A builder's guide to energy efficient homes in Georgia

A Builder's Guide to Energy Efficient Homes in Georgia
Georgia Environmental Facilities Authority

Builder's Guide to Energy Efficient Homes in Georgia
Georgia Environmental Facilities Authority, Division of Energy Resources Atlanta, Georgia September 1999

Third Edition--September 1999
Principal Authors Jeffrey S. Tiller, PE Dennis B. Creech
Technical Review Mike Barcik, Mike Andreyuk
Graphics and Desktop Composition Greg Brough
Publication Management Julie Simon
Research Assistants Suzie Spivey, Greg Sandine
For additional copies of this publication or other energy information, please contact:
Georgia Environmental Facilities Authority (GEFA) Division of Energy Resources (formerly known as the Governor's Office of Energy Resources) 100 Peachtree Street, Suite 2090 Atlanta, GA 30303 404-656-5176 FAX 404-656-7970 www.gefa.org
This publication was prepared under contract to the Georgia Environmental Facilities Authority, Division of Energy Resources by the Southface Energy Institute, Inc. Southface may be reached at:
Southface Energy Institute, Inc. 241 Pine Street Atlanta, GA 30308 404-872-3549 FAX 404-872-5009 www.southface.org
DISCLAIMER
This publication was prepared with funds made available within the guidelines of U.S. Department of Energy (DOE) Grant No. DE-FG44-77CS60212. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of DOE. The contents of this publication are offered as guidance. Neither the Georgia Environmental Facilities Authority/ Division of Energy Resources, nor any of their employees, contractors, subcontractors, or any technical sources referenced in this handbook makes any warranty or representation, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed or represents that its use would not infringe on privately owed rights. Reference to any trade names, manufacturer, specific commercial products, process, or service is for information or example only and does not constitute an endorsement or recommendation for use.

TABLE OF CONTENTS
1: Step-by-Step Energy Efficient Construction ............ 1 2: Why Build Efficiently? ............................................ 15 3: The House as a System ........................................... 19 4: Air Leakage--Materials and Techniques ............... 33 5: Insulation Materials and Techniques .................... 45 6: Windows and Doors .................................................71 7: Heating, Ventilation, Air Conditioning (HVAC) .... 85 8: Duct Design and Sealing ....................................... 105 9: Domestic Water Heating ........................................ 115 10: Appliances and Lighting ....................................... 121 11: Passive Solar Homes--Designs for Today ............ 127 Appendix 1: Mortgage Rate Tables ............................... 137 Appendix 2: Fingertip Facts .......................................... 141 Appendix 3: Earth Craft House .................................... 145 Appendix 4: Resources ................................................... 151

Step-by-Step Energy Efficient Construction

1. Step-by-Step Energy Efficient Construction

When properly used in home construction,
energy features save money, improve indoor air quality, enhance comfort, prevent moisture problems, and increase the long term durability of the building.
Key .eatures of Energy Efficient Homes
Create continuous air barrier system--eliminate leakage between conditioned and unconditioned spaces, in particular between living areas and crawl spaces, unheated basements, and attics.
Create continuous insulation barrier--install insulation as continuously as possible between conditioned and unconditioned spaces. Focus on:
s exterior walls
s floor systems over unconditioned or exterior spaces
s ceilings below unconditioned or exterior spaces
s wall areas adjacent to attic space--such as knee walls and attic stairways
s wall areas that extend into unheated basements--such as basement stairways
Select and install energy efficient windows
s design home with minimal east and west glass area, locate additional glass area on south side for passive heating in winter months
s use double-glazed windows with U-values under 0.60 (R-values of at least 1.65)

s consider low-emissivity coatings and other high performance features
s shade windows in summertime
Design heating and cooling system for efficiency
s select high efficiency equipment designed for local climatic conditions
s size and install equipment properly s eliminate potential for backdrafting of com-
bustion appliances s install fresh air ventilation systems to bring
in outside air when needed
Seal ductwork s size ductwork to meet the heating and cooling load of each room s lay out ductwork to supply proper airflow; measure airflow to guarantee comfort s seal all duct leaks, except those in removable components, with mastic or mastic plus fiber mesh s seal leaks around removable components with duct tape
Minimize water heating costs
Choose energy efficient appliances and lighting
Consider passive solar design to further reduce winter heating and summer cooling needs

Builders Guide to Energy Efficient Homes in Georgia

1

Step-by-Step Energy Efficient Construction
Building Section

Continuous ridge vent

Insulate knee walls R-19 to Install continuous air R-30 barrier on backside of insulation
All duct leaks sealed with mastic
Continuous R-30 attic insulation

Continuous R-25 to R-30 cathedral ceiling

Drywall forms continuous, airtight barrier

Seal ductwork penetrations

Recessed lights should be avoided; where used,
specify airtight, IC-rated fixtures
Soffit vent

Continuous insulation R-13
to R-21

Seal leaks into dropped
soffits
Continuous air barrier

Seal and insulate band
joists

HVAC unit properly sized

Minimum doubleglazed; low-e
windows preferred

Continuous insulated sheathing
R-2 to R-3.6
Earth slopes away from home

Seal all air leaks

R-19 to R-21 floor insulation

Seal all electrical penetrations

Continuous vapor barrier

2

Builders Guide to Energy Efficient Homes in Georgia

Site Planning

Step-by-Step Energy Efficient Construction

Gutter directs water from foundation

Low branching trees on east and west to shade in summer

South windows to let in sunlight during winter

Slope soil away from house
Minimal east and west windows

Continuous foundation drain in gravel bed with filter fabric connected to drain carrying
moisture away from foundation

Builders Guide to Energy Efficient Homes in Georgia

3

Step-by-Step Energy Efficient Construction
.ooting and .oundation Wall
1. If required, insulate footing and foundation wall--make trench wide enough for foam insulation board for basement. Confirm acceptance of foam insulation with local code inspector. Meet with a reputable termite treatment company and discuss treatment plan.
2. Install layer of polyethylene as a capillary break. 3. Set rebar as required and pour concrete. 4. Build foundation wall. 5. Waterproof below-grade portion of foundation wall and install drainage plane material if
conditioned spaces are on other side of wall. 6. If conditioned basement or rooms are located behind foundation wall, insulate exterior with
1 to 2 inches of foam insulation. Confirm acceptance with local code inspector and reputable termite company. 7. Cover perforated drain pipe with gravel. 8. Install filter fabric over drainage pipe and gravel. 9. When back filling foundation wall, slope earth away from house 5% on all sides.

6

5

4

9

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1
3 2

4

Builders Guide to Energy Efficient Homes in Georgia

.oundation Alternatives

Step-by-Step Energy Efficient Construction

A) For uninsulated crawl space walls--skip foam insulation and waterproofing. Drainage system is recommended.

Foundation drain

Concrete block

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Vapor barrier

B) Investigate insulated concrete foundation systems and insulated foam blocks--check with manufacturer carefully for recommended water proofing, type of termite treatments, concrete specifications, reinforcing requirements, and other stipulations. Confirm acceptance by local code official.

Foam insulation
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Waterproofing

C) Permanent wood foundation--use pressure treated (PT) plywood and framing lumber; waterproof outside, cover with polyethylene plastic, and insulate. Install drainage system and back fill carefully.

Air barrier (PT

plywood or

polyethylene

Plastic

caulked in place)

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Builders Guide to Energy Efficient Homes in Georgia

5

Step-by-Step Energy Efficient Construction
Crawl Space or Unconditioned Basement
1. Install operable foundation vents, as required by local codes, and close them year round. 2. Consider manufactured joists in place of dimensional lumber, such as 2x10s or 2x12s. 3. Set band joists and floor joists. 4. Glue subfloor in place, except use caulking:
s between band joist and subfloor, s around other openings and subfloor.
5. Seal all holes through floor as home is constructed. 6. Lay plastic moisture barrier on 100% of crawl space floor.

Subfloor Band joist Anchor bolt Pressure-treated sill plate Termite shield Gravel and drain tile Plastic vapor barrier
6

4

5

23

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6

Builders Guide to Energy Efficient Homes in Georgia

Step-by-Step Energy Efficient Construction
.loorConditioned Basement
See details for crawl space floors, plus: 1. Caulk under termite shield. 2. Set termite shield on top of foundation wall. 3. Lay sill sealant material. 4. Predrill pressure-treated sill plate--bolt in place. 5. Set band joists and floor joists. 6. Seal seam between band joist and sill plate with durable caulking--either between
joists and plates or from outside after floor framing is completed. Insulate band joist area. 7. Caulk subfloor to band joist and floor joists. 8. Waterproof wall and install drainage plane material plus drain tile adjacent to footing. 9. Install interior foam insulation or interior framed, insulated wall.

Interior Foam Insulation

Band joist seal (applied between joist and plate)

7

Subfloor

Sill sealant 6

4
3 2
1

Earth

8
Caulking

5
Band joist Anchor bolt Bottom plate Termite shield
Drywall
2" foam 9
Furring Strip

Builders Guide to Energy Efficient Homes in Georgia

Interior Framed, Insulated Wall
9
Sill plate sealed to band joist from outside
Framed wall built following wall insulation guidelines Band joist fully insulated
7

Step-by-Step Energy Efficient Construction
Insulated .loor

R-19 floor insulation
Rigid wire insulation supports Seal and insulate band joist area
Seal and insulate wall

Line of conditioned building envelope

Basement stairways (or other stairways or plenums from conditioned to unconditioned zones)--determine location of conditioned
building envelope. Provide a continuous layer of insulation and an air barrier across
the envelope.

8

Builders Guide to Energy Efficient Homes in Georgia

Wall .raming
Header detail
4

Step-by-Step Energy Efficient Construction
T-wall framing detail

5 6

3 2 1

1. In corners, use single stud corner or double stud corner when using wood siding with vertical cornerboard trim.
2. Use 1x4 or metal T-brace near corners.
3. At partition wall (T-wall) intersection, eliminate additional studs for nailing drywall; use "ladder" instead.
4. Add " foam to structural headers.
5. Cover entire wall with " foam sheathing, including band joists and second top plates.
6. Before lifting wall in place, install sill sealant material between wall and subfloor.

1
Drywall clip Corner framing detail with vertical corner board and wood siding permits
installation of corner insulation

Builders Guide to Energy Efficient Homes in Georgia

9

Step-by-Step Energy Efficient Construction
Ceiling Details

Raised top plate-- provides ample
room for insulation

Continuous coverage of
R-30 to R-38
insulation

Add blown insulation dam to obtain full height
at access, porches, etc.

Attic storage areas--add 2x4 framing on edge on top of joists to allow room for
insulation

Insulated attic cover--either attached to attic door or foam insulated cover

10

Builders Guide to Energy Efficient Homes in Georgia

Step-by-Step Energy Efficient Construction
Seal Holes and Penetrations

Seal plumbing penetrations
1 Locate plumbing on interior walls.
2. Use firestop rated caulk to seal holes into attic.
3. Seal under tubs and showers.
4. Caulk between drywall and piping penetrations.

4
2 1

3

2 1

4

Seal electrical penetrations

1. Seal holes through bottom plate of all walls.

2. Use firestop rated caulk to seal holes into attic.

3.
3 4.

Caulk between drywall and all electrical boxes, including receptacles, switches and lights.
Minimize use of recessed lights; where used choose IC (insulated cover) fixtures that also have airtight ratings.

Builders Guide to Energy Efficient Homes in Georgia

11

Step-by-Step Energy Efficient Construction
HVAC Systems

1. Size for heating and cooling load using Manual J techniques. 2. Size latent (dehumidification) load for cooling system. 3. Compare cost and projected energy savings of at least 3 HVAC contractor
bids and 3 equipment options: a. Minimum efficiency: SEER 10 cooling, AFUE .78 furnace, HSPF 6.8 heat
pump b. Moderate efficiency: SEER 12 cooling, AFUE .80 furnace, HSPF 7.2 heat
pump c. High efficiency: SEER 14 cooling, AFUE .90 furnace, HSPF 7.8 heat pump 4. Consider automatic zoned system instead of multiple separate systems. 5. When selecting a contractor, don't just go by price. Consider: a. reputation for quality b. type of duct system c. number of returns d. sound muffling components e. willingness to ensure and test for airtight ductwork

12

Builders Guide to Energy Efficient Homes in Georgia

Ductwork
1. Design using Manual D Concepts. 2. Install returns in each room with a
closeable door and more than one supply. 3. Seal all duct leaks with mastic or mastic and fiber mesh--use guidelines in Chapter 8. 4. Test ducts for air tightness. 5. Test home for pressure imbalance problems.

Step-by-Step Energy Efficient Construction
Pressure gauge Duct tester fan Fan control s w i tc h
Registers sealed with tape Duct Testing Fan Set-up

Removable tape

Mastic

Many air handler cabinets come from the factory with leaks. They should be sealed with duct-sealing mastic. Removable panels should be sealed with metal duct tape.

Attach flex-duct to take-off collar
with strap

Apply mastic to seal flex-duct to collar and collar
to plenum

Closed doors isolate supplies
from returns

Pull insulation and outer liner over sealed take-off;
strap outer liner in place

Prevent Pressure Imbalance Problems

Step-by-Step Duct Sealing

Builders Guide to Energy Efficient Homes in Georgia

13

Step-by-Step Energy Efficient Construction
Notes:

14

Builders Guide to Energy Efficient Homes in Georgia

Why Build Efficiently?

2. Why Build Efficiently?

Investments in energy efficient features in new
construction are remarkable because everyone wins:
s Homeowners receive a positive cash flow within 1 to 3 years.
s Homeownersbenefitadditionallyfromimproved comfort, better indoor quality, reduced moisture problems, and fewer health problems.
s Builders have fewer call-backs and make additional profit from the added value.
s Heating and cooling contractors have fewer call-backs.
s Realtors earn additional fees from the value added features and enhance their reputation by selling higher quality homes that consumers appreciate.
s Bankers generate higher mortgage payments for homes with lower annual costs of ownership due to the reduced energy bills.
s National lending agencies, such as the Federal Housing Authority (FHA), the Veteran's Administration (VA), and Fannie Mae offer preferred financing options to owners of energy efficient homes.
s The local economy benefits as more money stays within the community and local subcontractors and product suppliers make additional income by selling improved energy efficient features.
s Everyone enjoys reduced pollution from fossilfueled power plants and increases in national security from decreased demand for nonrenewable energy sources.

Achieving Efficiency
Energy efficient homes are no accident. Too often, measures that may be easier to market are installed, but key ingredients--such as sealing air leaks and duct leaks--are left undone. The results are homes that fall far short of the goals of a truly energy efficient home--energy bills higher than necessary, comfort and moisture problems, and homeowners who are thoroughly dissatisfied.
Designing and building a home that uses energy wisely does not mean sacrificing a home's aesthetics or amenities. Homes of any architectural style can meet the requirements of this book. Any good home design considers the characteristics of a particular site: the local climate, the availability and cost of energy sources, and the lifestyle of the occupants.
Building an energy efficient home requires no special materials or construction skills. However, the quality of basic construction has a major influence on building comfort and energy costs, especially:
s Quality of framing and installation of insulation and windows.
s Attention to detail in sealing air leaks.
s Design and installation of the heating and cooling equipment.
s Effectiveness of sealing duct leaks.
Table 2-1 shows the savings available for a "typical energy efficient home." The cumulative net savings are about $8,000 over a 30-year period. The investment begins providing a positive cash flow in the second year, once the additional downpayment for the energy feature, added into the first year's extra

Builders Guide to Energy Efficient Homes in Georgia

15

Why Build Efficiently?

mortgage has been paid. Table 2-2 shows the rate of return for energy investments with different payback periods.

Independent Home Energy Rating
Because most of the energy efficiency of a home is dependent on the quality of installation, purchasing a home energy rating provides the assurance of third party verification of your home's quality and savings. The Home Energy Rating System (HERS) is a national effort to train and certify home energy raters to evaluate the energy performance of homes.

Table 2-1 Savings from an Energy Efficient Home

Standard

Annual

Year Energy

Cost

1 $1,200

2

1,218

3

1,236

4

1,255

5

1,274

6

1,293

7

1,312

8

1,332

9

1,352

10 1,372

11 1,393

12 1,414

13 1,435

14 1,456

15 1,478

16 1,500

17 1,523

18 1,546

19 1,569

20 1,592

21 1,616

22 1,640

23 1,665

24 1,690

25 1,715

26 1,741

27 1,767

28 1,794

29 1,821

30 1,848

Energy Efficient

Extra

Annual Total

Mortgage Energy Cost

Cost

Cost

$526*

$850 $1,376

166

863 1,029

166

876 1,042

166

889 1,055

166

902 1,068

166

916 1,082

166

929 1,096

166

943 1,124

166

958 1,138

166

972 1,138

166

986 1,153

166

1,001 1,167

166

1,016 1,182

166

1,032 1,198

166

1,047 1,213

166

1,063 1,229

166

1,079 1,245

166

1,095 1,261

166

1,111 1,277

166

1,128 1,294

166

1,145 1,311

166

1,162 1,328

166

1,179 1,346

166

1,197 1,363

166

1,215 1,381

166

1,233 1,399

166

1,252 1,418

166

1,271 1,437

166

1,290 1,456

166

1,309 1,475

Cumulative Savings $(176) 13 208 407 613 824 1,040 1,491 1,725 1,725 1,965 2,211 2,464 2,722 2,987 3,259 3,537 3,622 4,113 4,412 4,717 5,029 5,349 5,676 6,010 6,352 6,701 7,058 7,423 7,796

*The extra mortgage costs are for financing energy efficient features. The first year costs are higher because they include the additional downpayment.

Home energy ratings involve an on-site inspection of a home by a residential energy efficiency professional, a home energy rater. Home energy raters are trained and certified by the operating home energy rating system. As a rule, home energy raters come from either the housing or energy fields. Their backgrounds include experience as home inspectors, appraisers, energy auditors, low-income weatherization contractors, and energy efficient home builders and designers.
The home energy rater inspects the home and measures its energy characteristics, such as insulation levels, window efficiency, window-to-wall ratios, the heating and cooling system efficiency, the solar orientation of the home, and the water heating system. Diagnostic testing, such as air leakage and duct leakage testing, is often part of the rating.

Table 2-2 Rate of Return for Energy Investments (%)

Payback (Years) 5
1.5 67 2 47 3 25 4 13 55 60 70 80 90 10 0 11 0 12 0 13 0 14 0 15 0 16 0 17 0 18 0 19 0 20 0

Lifetime of Energy Investments (Years) 7 10 12 15 17 20
73 73 75 75 75 75 53 57 57 57 57 57 22 37 39 39 39 39 21 27 29 29 31 31 14 20 22 25 25 25 9 15 18 20 20 21 5 12 14 16 17 18 1 9 12 14 15 16 0 7 9 12 13 14 0 5 8 10 11 13 0 3 6 9 10 11 0 1 4 8 9 10 003689 002578 001568 000457 000346 000246 000235 000134

Note: A zero indicates the rate of return is either negligible or negative. The table assumes energy prices escalate 4% per year.

16

Builders Guide to Energy Efficient Homes in Georgia

Why Build Efficiently?

The data gathered by the home energy rater is input into a computer program and translated into points. The home receives a score from 1 to 100, depending on its relative efficiency. An estimate of the home's energy costs is also provided. The home's energy rating is then given a star rating ranging from one star for a very inefficient home to five stars for a highly efficient home. Along with the rating sheet, a home owner receives a report listing cost-effective options for improving the home's energy rating.
Home energy rating is also a major component in most green builder programs. In addition to energy efficiency, these programs address other environmental concerns regarding home building, such as materials conservation, water efficiency, land preservation, waste management, and indoor air quality. Appendix 3 provides more information about Earth Craft HouseSM, a green building program now available in Georgia.
Home energy rating offers many benefits including:
s Verification of home quality
s Estimate of annual energy costs
s Design process tool to choose energy features
s Nationally-approved scoring system that allows home buyers to compare energy efficiency of homes
s Added value that increases the appraised value
s Compliance tool for the Model Energy Code adopted by Georgia
s Home certification for marketing programs such as ENERGY STAR and others
s Home certification for energy efficient mortgages (see below)
For more information on home energy ratings and a list of certified raters in Georgia, see Appendix 4.
.inancing Energy Efficiency
A useful tool is now available in Georgia to help finance energy efficiency features and solar technologies--energy efficient mortgages. With energy efficient mortgages, different finance options are available depending on the lender. These mortgages help make it easier for homebuyers to qualify for energy efficient homes or to afford a more costly home at a given income.

For example, preferred terms for homebuyers purchasing ENERGY STAR Homes through an ENERGY STAR Mortgage can include:
s Cash back at closing
s Increased debt-to-income ratio
s Assured appraisal values
s Free interest lock
s Reduced loan origination fees
s Discounted interest rates
Lenders of energy efficient mortgages usually require a home energy rating.
For more information on energy efficient mortgages and programs that currently operate in Georgia, please see Appendix 4.
The Georgia Energy Code
The Georgia Energy Code is based on the 1995 Model Energy Code, a national code developed by the Council of American Building Code Officials. The code has requirements for:
s Thermal insulation
s Air sealing
s HVAC system design
s Hot water conservation
s Duct insulation and sealing
Table 2-3 shows combinations of energy measures that will pass the code in different cities. The requirements allow the designer great flexibility as tradeoffs can be made between areas with too little insulation and those that exceed the code.
R-30 insulation is required for virtually all flat ceilings; however, allowances from 25% to 30% of the ceiling area are provided for R-19 cathedral ceilings. The only exception is the northernmost climatic zone where the builder must install R-38 insulation in the flat attic if R-19 cathedral ceilings are built.
Walls and window R-values vary substantially depending on the percentage of glass in the walls. Floors generally need R-13 to R-19 insulation.
The strength of the code is its breadth compared to previous versions. It includes specific air sealing measures for code compliance, going as far as to include three paragraphs on recessed lighting. In

Builders Guide to Energy Efficient Homes in Georgia

17

Why Build Efficiently?

addition, the duct requirements stipulate that duct sealing mastic must be used to seal leaks in the HVAC's air distribution system.
Compliance with statewide codes is required in all localities. Most home purchase contracts contain an assurance by the builder that the home complies with all applicable codes. Thus, all new homes built in Georgia should comply with the energy code.
A copy of the energy code can be found at the Georgia Department of Community Affairs website listed in Appendix 4.

Table 2-3 Designs That Meet The Georgia Energy Code

City

Flat Ceiling Insulation R-value

R-19 Cathedral Ceiling Area (% of Total Ceiling)

Wall Composite R-value

Window and Door Area (% of Total Wall)

Window R-value

Floor Insulation R-value

Valdosta R-30

30%

R-18 11.1% R-0.77 R-13

R-30

30%

R-13 19.8% R-1.49 R-13

Macon R-30

25%

R-16 13.5% R-0.77 R-13

R-30

25%

R-15 19.6% R-1.79 R-13

Atlanta R-30

25%

R-17 12.0% R-1.15 R-19

R-30

25%

R-15 18.4% R-1.92 R-19

Clayton R-30

0%

R-17 13.3% R-1.49 R-19

R-38 25%* R-20 16.9% R-1.79 R-19

* Flat attic must be R-38 if using 25% allowance for cathedral ceiling.

EVALUATING ENERGY EFFICIENT PRODUCTS

The energy efficient builder seeks to minimize the lifetime costs of a home rather than the first costs. Making such calculations is often time-consuming and confusing. One of the best ways to determine whether an investment is sound is to compare the annual energy savings with the additional annual mortgage costs to find the Net Annual Savings.
For example, suppose you are wondering whether it is worthwhile for a home to have high efficiency, low-e windows, which use special coatings to reduce heat loss and gain. A builder had planned to install double-glazed units, but is now considering an upgrade to low-e units. He receives the following information from a window dealer:
s Additional Window Cost = $500
s First Year Energy Savings = $75
He can easily calculate that the payback period on the above investment is just under 7 years. However, he is unsure whether the payback is acceptable. To find the Net Annual Savings, first, he finds the extra mortgage costs for the windows:
s Mortgage Interest Rate = 8.5%
s Term of Mortgage = 30 years
s Monthly Payment per $1,000 (from Appendix 1) = $7.69

s Annual Payment per $1 (multiply the above by 12 and divide by 1,000) = $.092
s Extra Annual Payment (multiply the additional cost of the windows by the above factor) = $500 * $.092 = $46
s Net Annual Energy Savings (subtract the annual payment from annual energy savings) = $75 - $46 = $29
Since the Net Annual Energy Savings is positive, the investment is sound, especially when considering that energy costs will increase over time, while mortgage costs will remain relatively constant.
It is often useful to calculate the Rate of Return (ROR) for an energy investment. Homeowners can compare the annual percentage return for an energy measure to that earned by their financial investment. The steps for finding the ROR, using the above example, are as follows:
1. Find the payback period (divide the total cost by the annual savings) = 500/75 = about 7 years
2. Determine the life of the energy measure = over 20 years
3. For the payback period and lifetime, find the ROR in Table 2-3 = 18% (and it's tax free)

18

Builders Guide to Energy Efficient Homes in Georgia

The House As A System

3. The House As A System

We sometimes think of our homes as indepen-
dent structures, placed on an attractive lot, and lived in without regard to the world around. Yet, most homes have problems--some minor nuisances, others life-threatening:
s Mold on walls, ceilings, and furnishings
s Mysterious odors
s Excessive heating and cooling bills
s High humidity
s Rooms that are never comfortable
s Decayed structural wood and other materials
s Termite or other pest infestations
s Fireplaces that do not draft properly
s High levels of formaldehyde, radon or carbon monoxide
These problems occur because of the failure of the home to properly react to the outdoor or indoor environment. The house should be designed to function well amid fluctuating temperatures, moisture levels, and air pressures.

Health and Comfort .actors
The following factors define the quality of the living environment. If kept at desirable levels, the house will provide comfort and healthy air quality.
s Moisture levels--often measured as the relative humidity (RH). High humidity causes discomfort and can promote growth of mold and organisms such as dust mites.
s Temperature--both dry bulb (that measured by a regular thermometer) and wet bulb, which indicates the amount of moisture in the air. The dry bulb and wet bulb temperatures can be used to find the relative humidity of the air.
s Air quality--the level of pollutants in the air, such as formaldehyde, radon, carbon monoxide, and other detrimental chemicals, as well as organisms such as mold, pollen, and dust mites. The key determinant of air quality problems is the strength of the source of pollution.
s Air movement--the velocity at which air flows in specific areas of the home. Higher velocities make occupants more comfortable in summer, but less comfortable in winter.
s Structural integrity--the ability of the materials that make up the home to create a long-term barrier between the exterior and inside.

Builders Guide to Energy Efficient Homes in Georgia

19

The House As A System

Concepts
Heat .lows in Homes
The health and comfort factors are affected considerably by how readily heat moves through a home and its exterior envelope. The sidebar explains the three primary modes of heat transfer.
New homes in Georgia are required to meet the Georgia Energy Code, which requires insulation on all exterior surfaces--floors, walls, and ceilings. As shown in Table 3-1, when the thermal envelope is well insulated, air leakage and duct leakage problems become the major sources of heat loss and gain.
In summer, the cooling needs are driven by the location and shading of windows. Also, the percentage of the cooling load that is for latent cooling (humidity removal) can increase substantially in homes with a well insulated thermal envelope. The major sources of moisture, some of which can be controlled, include cooking activities, human respiration and perspiration, and infiltration of hot, humid, exterior air.

Table 3-1: Typical Home Energy Use (Percentage of Total Energy Bill)*

Standard Home

Home with Improved Insulation

Heating Conduction Air Leakage

37% 26% 11%

31% 18% 13%

Cooling Conduction Air Leakage Solar Gain Internal Gain Latent Cooling
(dehumidification)

35% 8% 3% 12% 3% 9%

31% 5% 2% 9% 4% 11%

Other Hot Water Appliances Lighting

28% 14% 6% 8%

38% 19% 8% 11%

* Percentages will vary according to the local climate, choice of energy source, and building design.

HOW HEAT MOVES
Conduction
s The transfer of heat through solid objects, such as the ceiling, walls, and floor of a home.
s Insulation (and multiple layers of glass in windows) reduce conduction losses.
Convection
s The flow of heat by currents of air.
s As air becomes heated it rises; as it cools, it becomes heavier and sinks.
s The convective flow of air into a home is known as infiltration; the outward flow is called exfiltration. In this book, this air flow is known generally as air leakage.
Radiation
s The movement of energy in waves from warm to cooler objects across empty spaces.
s Examples include radiant heat traveling from:
inner panes of glass to outer panes in double-glazed windows in winter
roof deck to attic insulation during hot, sunny days
s Can be minimized by installing reflective barriers; examples include radiant heat barriers in attics and low-emissivity coatings for windows.

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Air Leaks and Indoor Air Quality
Both building professionals and homeowners have concerns about indoor air quality. It is important to understand that few studies on the subject have shown a strong relationship between indoor air quality and the air tightness of a home.
The major factor affecting indoor air quality is the level of the pollutant causing the problem. Thus, most experts feel that the solution to poor indoor air quality is removing the source of the pollution. Building a leakier home may or may not help lessen the intensity of the problem, but it will not eliminate it, nor necessarily create a healthy living situation.
Air leaks often bring in air quality problems from outside, such as:
s Mold from crawl spaces and outdoors
s Radon from crawl spaces and under-slab areas
s Humidity from crawl spaces and outdoor air
s Pollen and other allergens from outdoor air
s Dust and other particles from crawl spaces and attics
The best solution to air quality problems is to build a home as tightly as possible and install an effective ventilation system that can bring in fresh outside air (not crawl space or attic air). Ventilation system design options and indoor air quality are described in greater detail in Chapter 7.
.igure 3-1: Air Quality Problems from ".resh" Air
in a Leaky House

.igure 3-2: Conditions for Condensation
Surface at or below dew point of air
Air at given temperature and relative humidity
Condensation

How Condensation Occurs

Air is made up of gases such as oxygen, nitrogen, and water vapor. The amount of water vapor that air can hold is determined by its temperature. Warm air can hold more vapor than cold air. The amount of water vapor in the air is measured by its relative humidity. At 100% RH, water vapor condenses into a liquid. The temperature at which water vapor condenses is its dewpoint.

RH =

the amount of water vapor in the air at a given temperature
the maximum amount of water vapor that air can hold at that temperature

Humidity Dust

Dust Insulation, Humidity

Pollen Allergens

The dew point of air depends on its temperature and relative humidity. A convenient tool for examining how air, temperature and moisture interact is the Psychrometric Chart, explained in the sidebar Understanding Relative Humidity. Preventing condensation involves reducing the RH of the air or increasing the temperatures of surfaces exposed to the air.

Mold, Radon Humidity, Pesticides

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MOISTURE AND RELATIVE HUMIDITY
A psychrometric chart aids in understanding the dynamics of moisture control. A simplified chart shown in Figure 3-3 relates temperature and moisture. Note that at a single temperature, as the amount of moisture increases (moves up the vertical axis), the relative humidity of the air also increases. At the top curve of the chart, the relative humidity reaches 100%--air can hold no additional water vapor at that temperature, called the dew point, so condensation can occur.
Winter Condensation in Walls
In a well built wall, the temperature of the inside surface of the sheathing will depend on the insulating value of the sheathing, and the indoor and outdoor temperatures. When it is 35oF outside and 70oF at 40% relative humidity inside:
s The interior surface of plywood sheathing will be around 39oF
s The interior surface of insulated sheathing would be 47oF
The psychrometric chart can help predict whether condensation will occur:
1. In Figure 3-4, find the point representing the indoor air conditions
2. Draw a horizontal line to the 100% RH line
3. Next, draw a vertical line down from where the horizontal line intersects the 100% RH line
In the example, condensation would occur if the temperature of the inside surface of the sheathing were at 44oF. Thus, under the temperature conditions in this example, water droplets may form on the plywood sheathing, but not on the insulated sheathing.
Summer Condensation in Walls
Figure 3-5 depicts a similar case in summer. If the interior air is 75oF, and outside air at 95oF and 40% relative humidity enters the wall cavity, will condensation occur? Using the psychrometric chart we find that the dew point of the outside air leaking into the wall cavity would be about 67oF. Since the drywall temperature is greater than the dew point, condensation should not form.

Figure 3-3 Psychrometric Chart
Figure 3-4 Winter Dewpoint Temperature Inside Walls
Figure 3-5 Summer Dewpoint Temperature Inside Walls

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Effect of Relative Humidity

Structural System

Humans respond dramatically to changes in relative humidity (RH):
s At lower RH, we feel cooler as moisture evaporates more readily from our skin.
s At higher levels, we may feel uncomfortable, especially at temperatures above 78 degrees.
s Dry air can often aggravate respiratory problems.
s Molds grows in air over 70% RH. s Dust mites prosper at over 50% RH. s Wood decays when the RH is near or at 100%. s Ideal health and comfort for humans occurs at
30% to 50% RH.
Systems in a Home
Whether the health and comfort factors of temperature, humidity, and air quality remain at comfortable and healthy levels depends on how well the home works as a system. Every home has systems that are intended to provide indoor health and comfort:
s Structural system s Moisture control system s Air barrier system s Thermal insulation system s Comfort control system

The purpose of this book is not to show how to design and build the structural components of a home, but rather to describe how to maintain the integrity of these components. Key problems that can affect the structural integrity of a home include:
s Frost heaving
s Erosion
s Roof leaks
s Water absorption into building systems
s Excessive relative humidity levels
s Fire
s Summer heat build-up
Structural recommendations
To prevent these structural problems, the home designer and builder should:
s Ensure that the footer is installed level and below the frost line. Install adequate reinforcing and make sure the concrete has the proper slump and strength.
s Divert ground water away from the building through a properly designed and installed foundation drainage system and install effective gutters, downspouts, and rain water drains. Specifications are shown in Chapter 1 and are described as well in the later discussion of moisture control systems.
s Ensure the roof is watertight to prevent rainwater intrusion. The homeowner should clean gutters and drainage piping regularly.
s Seal penetrations that allow moisture to enter the building envelope via air leakage. Use firestopping sealants to close penetrations that are potential sources of "draft" during a fire.
s Prevent air from washing over attic insulation.
s Install a series of capillary breaks that keep moisture from migrating through foundation systems into wall and attic framing.

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The House As A System

Moisture Control System

Homes should be designed and built to provide comfortable and healthy levels of relative humidity. They should also prevent both liquid water and water vapor from migrating through building components.
The moisture control system includes quality construction to shed water from the home and its foundation, vapor and air barrier systems that hinder the flow of water vapor, and heating and cooling systems designed to provide comfort throughout the year.
There are four primary modes of moisture migration into our homes. Each of these must be controlled to preserve comfort, health, and building durability.
Bulk moisture transport

Gaps Between Horizontal Siding

.igure 3-7 Capillary Action
Membrane serving as a capillary break should have been
installed
Capillary Action through Porous
Materials

s The flow of moisture through holes, cracks, or gaps
s Primary source is rain s Causes include:
Poor flashing Inadequate drainage Poor quality weatherstripping or caulking
around joints in building exterior (such as windows, doors, and bottom plates) s Solved through quality construction with durable materials s Most important of the four modes of moisture migration
.igure 3-6 Bulk Moisture Transport
Openings in Building Envelope
Poor Drainage

Capillary action
s Wicking of water through porous materials or between small cracks
s Primary sources are from rain or ground water
s Causes include:
water seeping between overlapping pieces of exterior siding
water drawn upward through pores or cracks in concrete slabs
water migrating from crawl spaces into attics through foundation walls and wall framing
s Solved by completely sealing pores or gaps, increasing the size of the gaps (usually to a minimum of 1/8 inch), or installing a water proof, vapor barrier material to form a capillary break

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Air transport

Vapor diffusion

s Unsealed penetrations and joints between conditioned and unconditioned areas allow air containing water vapor to flow into enclosed areas. As shown in Figure 3-8, air transport can bring 50 to 100 times more moisture into wall cavities than vapor diffusion.
s Primary source is water vapor in air s Causes include air leaking through holes,
cracks, and other leaks between:
interior air and enclosed wall cavities interior air and attics exterior air and interior air, adding humid-
ity to interior air in summer crawl spaces and interior air s Solved by creating an Air Barrier System
.igure 3-8 Typical Water Vapor Transport (100 sq ft Wall Without a Vapor Barrier)

s Water vapor in air moves through permeable materials (those having Perm ratings over 1)
s Primary source is water vapor in the air
s Causes:
interior moisture permeating wall and ceiling finish materials
exterior moisture moving into the home in summer
moist crawl space air migrating into the home
s Solved by proper installation of a vapor barrier; sample materials are shown in Table 3-2. In Middle and North Georgia, vapor barriers are recommended on the inside surface (warm-inwinter side) of floors, walls, and ceilings. However, in South Georgia, vapor barriers are not necessarily recommended.
s Least important of the four modes of moisture migration.

Vapor Diffusion: 2/3 pint per
heating season
Air Leakage (1/2" hole): 50 pints of water per
heating season

.igure 3-9 Vapor Barrier Recommendations
Use vapor barrier on warm-in winter
side

Table 3-2 Perm Ratings of Different Materials

Asphalt-coated paper backing on insulation Polyethylene plastic (6 mil) Plywood with exterior glue Plastic-coated insulated foam sheathing Aluminum foil (.35 mil) Vapor barrier paint or primer Drywall (unpainted)

0.40 0.06 0.70 under 0.30 0.05 0.45 50.0

No vapor barrier No vapor barrier or external vapor barrier
From the ASHRAE Handbook of Fundamentals, 1993, page 21.12.

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MOISTURE PROBLEM EXAMPLE
The owner of a residence in Georgia complains that her ceilings are dotted with mildew. On closer examination, an energy inspector finds that the spots are primarily around recessed lamps located close to the exterior walls of the building.
What type of moisture problem may be causing the mildew growth, which requires relative humidities over 70%? In reality, any of the forms of moisture transport could cause the problem:
Bulk moisture transport--the home may have roof leaks above the recessed lamps.
Capillary action--the home may have a severe moisture problem in its crawl space or under a slab. Via capillary action, moisture travels up the slab, into the framing lumber, and all the way into the attic. If the attic air becomes sufficiently moist, it may condense on the surface of the cool roof deck and drip onto the insulation and drywall below.
Air transport--most recessed lamps are quite leaky; if the air leaking into the attic is relatively warm and moist, and the roof deck is cool, the water vapor in the air may condense and drip onto the drywall. This is the most likely explanation.
Vapor diffusion--the home's ceiling may not have an adequate vapor barrier in the vicinity of the recessed lamps, causing excessive vapor flow into the attic. This is the least likely explanation.

Capillary Action

3. Excess humidity in attic

4. Roof deck cool-- condensation forms

2. Wood fibers carry moisture
to attic via capillary action

1. Severe moisture in crawl space

Air Transport
2. Moisture laden air hits roof deck -
condensation occurs

1. Air leak

Bulk Moisture Transport Roof leak

Vapor Diffusion

2. Excess humidity

3. Condensation

1. Vapor diffusion

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Air Barrier System
Air leakage can be detrimental to the long term durability of homes. It can also cause a substantial number of other problems, including:
s High humidity levels in summer and dry air in winter.
s Allergy problems. s Radon entry via leaks in the floor system. s Mold growth. s Drafts. s Window fogging or frosting. s Excessive heating and cooling bills. s Increased damage in case of fire.
An air barrier system may sound formidable, but it is actually a simple concept--seal all leaks between conditioned and unconditioned spaces with durable materials. Achieving success can be difficult without diligent efforts, particularly in homes with multiple stories and changing roof lines.
Air barriers may also help a home meet local fire codes. One aspect of controlling fires is preventing oxygen from entering a burning area. Most fire codes have requirements to seal air leakage sites.
Chapter 4 describes a number of air barrier systems--all can be effective with proper installation. They are one of the key features of an energy efficient home. The basic approach is:
s Seal all air leakage sites between conditioned and unconditioned spaces:
caulkorotherwisesealpenetrationsforplumbing, electrical wiring, and other utilities
seal junctions between building components, such as bottom plates and band joists between conditioned floors
consider air sealing insulating materials, such as cellulose or plastic foam
s Seal bypasses--hidden chases, plenums, or other air spaces through which attic or crawl space air leaks into the home.
s Install a continuous air barrier material such as the airtight drywall approach or the continuous polyethylene air barrier system.
Builders Guide to Energy Efficient Homes in Georgia

.igure 3-10 Air Barrier System Requirements
Seal all penetrations
Seal bypasses at attic floor and crawlspace/ unheated basement ceiling
Install continuous air barrier system 27

The House As A System

Thermal Insulation System

HVAC System

Thermal insulation and energy efficient windows are intended to reduce heat loss and gain due to conduction. As with other aspects of energy efficient construction, the key to a successfully insulated home is quality installation.
Substandard insulation not only inflates energy bills, but may create comfort and moisture problems. Key considerations for effective insulation include:
n Install R-values equal to or exceeding the Georgia Energy Code.
n Do not compress insulation.
n Provide full insulation coverage of the specified R-value; gaps dramatically lower the overall R-value and can create areas subject to condensation.
n Prevent air leakage through insulation--in some insulation materials, R-values decline markedly when subject to cold or hot air leakage.
n Air seal and insulate knee walls and other attic wall areas with a minimum of R-19 insulation.
n Support insulation so that it remains in place, especially in areas where breezes can enter or rodents may reside.

The heating, ventilation, and air conditioning system is designed to provide comfort and improved air quality throughout the year, particularly in winter and summer. Energy efficient homes, particularly passive solar designs, can reduce the number of hours during the year when the HVAC systems are needed.
These systems are often not well designed and may not be installed to perform as intended. As a consequence, homes often suffer higher heating and cooling bills and more areas with discomfort than necessary. Poor HVAC design often leads to moisture and air quality problems, too.
One major issue concerning HVAC systems is their ability to create pressure imbalances in the home. The sidebar on the following page shows that duct leaks can create serious problems. In addition, even closing a few doors can create situations that may endanger human health.
Pressure imbalances can increase air leakage, which may draw additional moisture into the home. Proper duct design and installation helps prevent pressure imbalances from occurring.
HVAC systems must be designed and installed properly, and maintained regularly by qualified professionals to provide continued efficient and healthy operation.

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DUCT LEAKS AND INFILTRATION
Forced-air heating and cooling systems should be balanced--the amount of air delivered through the supply ducts should be equal to that drawn through the return ducts. If the two volumes of air are unequal, pressure imbalances may occur in the home, resulting in increased air leakage and possible health and safety problems.

If supply ducts in unconditioned areas have more leaks than return ducts:
s Heated and cooled air will escape to the outside, increasing energy costs.
s Less air volume will be "supplied" to the house, so the pressure inside the house may become negative, thus increasing air infiltration.
s The negative pressure can actually backdraft flues--pull exhaust gases back into the home from fireplaces and other combustion appliances. The health effects can be deadly if flues contain substantial carbon monoxide.
If return ducts in unconditioned spaces leak:
s The home can become pressurized, thus increasing air leakage out of the envelope.
s Hot, humid air is pulled into the ducts in systems in summer; cold air is drawn into the ducts in winter.
s Human health may be endangered if ducts are located in areas with radon, mold, or toxic chemicals

Balanced Air Distribution
from soil termite treatments, paints, cleansers, and pesticides.
s If combustion appliances are located near return leaks, the negative pressure created by the leaks can be great enough to backdraft flues and chimneys.
Pressure differences can also result in homes with tight ductwork if the home only has one or two returns. When interior doors are closed it may be difficult for the air in these rooms to circulate back to the return ducts. The pressure in the closed-off rooms increases, and the pressure in rooms open to the returns decreases.
Installing multiple returns, "jumper" ducts that connect closed off rooms to the main return, and undercutting doors to rooms without returns will alleviate these problems.

Air Leaks in Supply Ducts

Air Leaks in Return System

Return Blocked by Door

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The House As A System

WALL MOISTURE EXAMPLE
The following pages describe two examples of building science problems due to common failures of the home's systems. These problems can be minimized through careful attention to the construction techniques described in this book.
A homeowner notices that paint is peeling on the exterior siding near the base of a bathroom wall. The drywall interior has mildew and the baseboard paint is peeling as well. What happened?
1. The interior of the wall has numerous air leaks-- an air barrier system failure.
2. The door to the bathroom is usually closed. When the heating and cooling system operates, the room becomes pressurized, as it has no return and its door is not undercut at the bottom. This is an HVAC system failure.
3. The bath fan is installed improperly and does not exhaust moist air--another HVAC system failure.
4. When air leaks into the wall, it carries substantial water vapor, thus the failure of the air barrier and HVAC systems has led to a moisture control system failure.
5. The interior wall has a polyethylene vapor barrier, which is not an air barrier. The exterior wall has CDX plywood sheathing, which is a vapor barrier.

6. When the air leaks carry water vapor into the wall cavity, the two vapor barriers hinder drying--a moisture control system failure.
7. In winter, the inner surface of the plywood sheathing will be several degrees cooler than foam sheathing would have been. Thus, the plywoodsheathed wall has more potential for condensation--a thermal insulation system failure.
8. As the water vapor condenses on the sheathing, it runs down the wall and pools on the bottom plate of the wall. Now the following problems occur:
s The water threatens to cause structural problems by rotting the wall framing.
s It wets the drywall, causing mold to grow.
s It travels through the unsealed back surfaces of the wood siding and baseboard, causing the paint to peel when it soaks through the wood.
s The multiple failures of the building systems create a potential structural disaster.
To solve this moisture problem the builder must address all of the failures. If only one aspect is treated, the problem may even become worse.

Air leaks around electrical and plumbing
Drywall Baseboard
Polyethylene vapor barrier with hole around electrical outlet

Plywood sheathing
R-13 batt insulation
Moisture-laden air touches cool plywood sheathing--
condensation occurs and water pools on bottom plate

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CARBON MONOXIDE DISASTER
1. A home has been built to airtight specifications--an air barrier system success.
2. However, the home's ductwork was not well sealed-- a HVAC system failure. It has considerably more supply leakage than return leakage which creates a strong negative pressure inside the home when the heating and cooling system operates.
3. The homeowners are celebrating winter holidays. With overnight guests in the home, many of the interior doors are kept closed. The home has only a single return in the main living room.
4. When the system operates, the rooms with closed doors become pressurized, while the central living area with the return becomes significantly depressurized. Because the house is very airtight, it is easier for these pressure imbalances to occur.
5. The home has a beautiful fireplace without an outside source of combustion air. When the fire in the unit begins to dwindle, the following sequence of events could spell disaster for the household.

s The fire begins to smolder and produces considerable carbon monoxide.
s Because the fire's heat dissipates, the draft pressure, which draws gases up the flue, decreases.
s Thereducedoutputofthefirecausesthethermostat to turn on the heating system. Due to the duct problems, the blower creates a relatively high negative pressure in the living room.
s Because of the reduced draft pressure in the fireplace, the negative pressure in the living room causes the chimney to backdraft--the flue gases are drawn back into the home. They contain carbon monoxide and can now cause severe, if not fatal, health consequences for the occupants.
This example is extreme, but similar conditions occur in a number of Georgia homes each year. The solution to the problem is not to build leakier homes--they can experience similar pressure imbalances. Instead, eliminate the causes of pressure imbalances, as described in detail in Chapter 7, and install an external source of combustion air for the fireplace.

5
Chimney backdrafts
Carbon monoxide in indoor air

Airtight construction
1

4

CO

3

2 Excess
supply leaks

High negative pressure in living room
Interior doors closed

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Notes:

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4. Air Leakage Materials and Techniques

Air leakage is a major problem for both new and
existing homes and can:
s Contribute over 30 percent of heating and cooling costs.
s Create comfort and moisture problems.
s Pull pollutants such as radon and mold into homes.
s Serve as a prime entry for insects and rodents.
To reduce air leakage effectively requires a continuous air barriersystem-- acombinationofmaterialslinkedtogether to create a tight building envelope. An air barrier also minimizes air currents inside the cavities of the building envelope which helps maintain insulation R-values.
The air barrier should seal all leaks through the building envelope--the boundary between the conditioned portion of the home and the unconditioned area. Most standard insulation products are not effective at sealing air leakage. The R-value for this material may drop if air leaks through the material.
Some spray applied insulation materials can seal against air leakage. However, these materials are often only applied in framing cavities; therefore additional air sealing must be done between framing components.
The builder should work with his or her own crew and subcontractors to seal all holes through the envelope. Then, he or she should install a continuous material, such as drywall, around the envelope. It is critical in the air sealing process to use durable materials and install them properly.

Materials
Most air barrier systems rely on a variety of caulks, gaskets, weatherstripping, and sheet materials, such as plywood, drywall, polyethylene plastic, and housewraps. The extra cost of these materials is usually under $500 for standard house designs.
.igure 4-1 Creating a Continuous Air Barrier
Boundary of building envelope
1. Install continuous insulation 2. Seal penetrations and bypasses 3. Install drywall or polyethylene as air barrier

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Table 4-1 Leaks and Sealants

Type of Leak
Thin gaps between framing and wiring, pipes or ducts through floors or walls
Leaks into attics, cathedral ceilings, wall cavities above first floor
Gaps, or cracks or holes over 1/8 inch in width not requiring firestop sealant

Commonly Used Sealants 40-year caulking; one-part polyurethane is recommended Firestop caulking, foam sealant
Gasket, foam sealant, or stuff with fiberglass or backer rod, and caulk on top

Open areas around flues, chases, plenums, plumbing traps, etc.
Final air barrier material

Attach and caulk a piece of plywood or foam sheathing material that covers the entire opening. Seal penetrations. If a flue requires a non-combustible clearance, use a noncombustible metal collar, sealed in place, to span the gap
Install Airtight Drywall Approach, polyethylene sealed in place, or other air barrier system

Seal Penetrations and Bypasses

.igure 4-2 Air Leakage Through Bypass

Dropped soffit

Chase for ducts or flues

The first step for successfully creating an air barrier system is to seal all of the holes in the building envelope. Too often, builders concentrate on air leakage through windows, doors, and walls, and ignore areas of much greater importance. Many of the key sources of leakage--called bypasses-- are hidden from view behind soffits for cabinets, bath fixtures, dropped ceilings, chases for flues and ductwork, or insulation. Attic access openings and whole house fans are also common bypasses. Sealing these bypasses is critical to reducing air leakage in a home and maintaining the performance of insulation materials.
The guidelines that follow in Figure 4-3 show important areas that should be sealed to create an effective air barrier. The builder must clearly inform his or her subcontractors and workers of these details to ensure that the task is accomplished successfully.

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.igure 4-3 Typical Home Air Leakage Sites

18 9

12 13 11
8

14

67

15

10

5

16

19

43 2

17 1
;y;y;y;y;y;y;y;y;y;y;y;y;y;y;y;y;y;y;y

1. Slab Floors-- seal all holes in the slab to prevent entry of water vapor and soil gas. A 4- to 6-inch layer of gravel under the slab is important to stop the seepage of water by capillarity.
2. Sill Plate and Rim Joist-- seal sill plates in basements and unvented crawl spaces. Caulk or gasket rim or band joists between floors in multi-story construction.
3. Bottom Plate-- use either caulk or gasket between the plate and subflooring.
4. Subfloor-- use an adhesive to seal the seams between pieces of subflooring.
5. Electrical Wiring-- use wire-compatible caulk or spray foam to seal penetrations.
6. Electrical Boxes-- use approved caulk to seal wiring on the outside of electrical boxes. Seal between the interior finish material and boxes.
7. Electrical Box Gaskets-- caulk foam gaskets to all electrical boxes in exterior and interior walls before installing coverplates.

8. Recessed Light Fixtures-- consider using surface-mounted light fixtures rather than recessed lights. When used, specify airtight models rated for insulation coverage (IC).
9. Exhaust Fans-- seal between the fan housing and the interior finish material. Choose products with tight-fitting backdraft dampers.
10. Plumbing--locate plumbing in interior walls, and minimize penetrations. Seal all penetrations with foam sealant or caulk.
11. Attic Access -- weatherstrip attic access openings. For pull-down stairs, use latches to hold the door panel tightly against the weatherstripping. Cover the attic access opening with an insulated box.
12. Whole House Fan-- use a panel made of rigid insulation or plastic to seal the interior louvers.
13. Flue Stacks--install a code-approved flue collar and seal with fire-rated caulk.
14. Combustion Appliances-- closely follow local codes for firestopping measures, which reduce air leakage as well as increase the safety of the appliance. Make certain all combustion appliances, such as stoves, inserts, and fireplaces, have an outside source of combustion air and tight-fitting dampers or doors.
15. Return and Supply Registers--seal all boots connected to registers or grilles to the interior finish material.
16. Ductwork-- seal all joints in supply and return duct systems with mastic.
17. Air Handling Unit (for heating and cooling system)--seal all cracks and unnecessary openings with mastic. Seal service panels with tape.
18. Dropped Ceiling Soffit-- use sheet material and sealant to stop air leakage from attic into the soffit or wall framing, then insulate.
19. Chases (for ductwork, flues, etc.)--prevent air leakage through these bypasses with sheet materials and sealants.

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.igure 4-4 Sealing Bypasses

Drywall extends behind bathtub

Major leak sealed Plumbing - Seal penetrations, especially under bathtubs and other fixtures. Install drywall,
plastic, or housewrap behind bathtub to provide an air barrier.
Drywall or plywood covers air leakage path

Dropped Ceiling Soffit - If kitchen cabinets or bath/shower enclosures have dropped soffits, provide a continuous seal at the attic floor.

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.igure 4-5 Sealing Bypasses for .lues and Ductwork

non-combustible flue

flue

collar (sheet metal)

plywood

Chases - Framed chases for flues should be sealed at the attic floor. Use a continuous layer of plywood or other solid sheet-good. Seal between the flue and combustible materials with fire-rated
caulk and a noncombustible flue collar.
sheet-good
sealant

Return and Supply Plenums - Seal framed areas for ductwork.

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Infiltration ControlMaterials and Techniques

AIR LEAKAGE DRIVING FORCES
Requirements for air leakage to occur:
s Holes--the larger the hole, the greater the air leakage. Large holes have higher priority for air sealing efforts.
s Driving force-- a pressure difference that forces air to flow through a hole. Holes that experience stronger and more continuous driving forces have higher priority.
The common driving forces are:
s Wind--caused by weather conditions.
s Stack effect--upward air pressure due to the buoyancy of air.
s Mechanical blower--induced pressure imbalances caused by operation of fans and blowers.
Wind is usually considered to be the primary driving force for air leakage. When the wind blows against a building, it creates a high pressure zone on the windward areas. Outdoor air from the windward side infiltrates into the building while air exits on the leeward side. Wind acts to create areas of differential pressure which cause both infiltration and exfiltration. The degree to which wind contributes to air leakage depends on its velocity and duration.
The temperature difference between inside and outside causes warm air inside the home to rise while cooler air falls, creating a driving force known as the stack effect. The stack effect is weak but always present. Most homes have large holes into the attic and crawl space or basement. Because the stack effect is so prevalent and the holes through which it drives air are often so large, it is usually a major contributor to air leakage, moisture, and air quality problems.
Poorly designed and installed forced-air systems can create strong pressure imbalances inside the home which can triple air leakage whenever the heating and cooling system operates. In addition, unsealed ductwork located in attics and crawl spaces can draw pollutants and excess moisture into the home. Correcting duct leakage problems is critical when constructing an energy efficient home.

.igure 4-6 Wind Driven Infiltration
On average, wind in the Southeast creates a pressure difference of 10 to 20 Pascals on the windward side. However, most homes have only small cracks on the exterior.
.igure 4-7 The Stack Effect
The stack effect can create pressure differences between 1 to 3 Pascals due to the power of rising warm air. Crawl space and attic holes are often large.
.igure 4-8 Mechanical System Driven Infiltration
Leaks in supply and return ductwork can cause pressure differences of up to 30 Pascals. Exhaust equipment such as kitchen and bath fans and clothes dryers can also create pressure differences.

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Builders Guide to Energy Efficient Homes in Georgia

Infiltration ControlMaterials and Techniques

MEASURING AIRTIGHTNESS WITH A BLOWER DOOR

While there are many well known sources of air leakage, virtually all homes have unexpected air leakage sites called bypasses. These areas can be difficult to find and correct without the use of a blower door. This diagnostic equipment consists of a temporary door covering which is installed in an outside doorway and a fan which pressurizes (forces air into) or depressurizes (forces air out of) the building. When the fan operates, it is easy to feel air leaking through cracks in the building envelope. Most blower doors have gauges which can measure the relative leakiness of a building.
One measure of a home's leakage rate is air changes per hour (ACH), which estimates how many times in one hour the entire volume of air inside the building leaks to the outside. For example, a home that has 2,000 square feet of living area and 8-foot ceilings has a volume of 16,000 cubic feet. If the blower door measures leakage of 80,000 cubic feet per hour, the home has an infiltration rate of 5 ACH. The leakier the house, the higher the number of air changes per hour, the higher the heating and cooling costs, and the greater the potential for moisture, comfort, and health problems.
To determine the number of air changes per hour, many experts use the blower door to create a negative pressure of 50 Pascals. A Pascal is a small unit of pressure about equal to the pressure that a pat of butter exerts on a piece of toast--about 0.004 inches water gauge. Fifty Pascals is approximately equivalent to a 20 mile-per-hour wind blowing against all surfaces of the building. Energy efficient builders should strive for fewer than 5 air changes per hour at 50 Pascals pressure (ACH50).

.igure 4-9 Blower Door

Gauges
Pressure measurement tubes
Door cover
Fan

Table 4-2 Typical Infiltration Rates .or Homes
(in air changes per hour at 50 Pascals - ACH50)

New home with special airtight construction and a controlled ventilation system

1.5 - 2.5

Energy efficient home with continuous air barrier system
Standard new home
Standard existing home
Older, leaky home

4.0 - 6.0
7.0 - 15.0 10.0 - 25.0 20.0 - 50.0

Builders Guide to Energy Efficient Homes in Georgia

39

Infiltration ControlMaterials and Techniques

Airtight Drywall Approach
The Airtight Drywall Approach (ADA) is an air sealing system that connects the interior finish of drywall and other building materials together to form a continuous barrier. ADA has been used on hundreds of houses and has proven to be an effective technique to reduce air leakage as well as keep moisture, dust, and insects from entering the home.
In a typical drywall installation, most of the seams are sealed by tape and joint compound. However, air can leak in or out of the home in the following locations:
s Between the edges of the drywall and the top and bottom plates of exterior walls.
s From inside the attic down between the framing and drywall of partition walls.
s Between the window and door frames and drywall.
s Through openings in the drywall for utilities and other services.
ADA uses either caulk or gaskets to seal these areas and make the drywall a continuous air barrier system.

.igure 4-10 Airtight Drywall Approach Air Barrier

Drywall Clip

For exterior walls seal at top and bottom plates

Seal all penetrations

Seal electrical boxes to drywall
For interior walls seal at top plate

ADA Advantages
Effective--ADA has proven to be a reliable air barrier.
Simple--does not require specialized subcontractors or unusual construction techniques. If gasket materials are not available locally, they can be shipped easily.
Does not cover framing--the use of ADA does not prevent the drywall from being glued to the framing.
Scheduling--gaskets can be installed anytime between when the house is "driedin" and the drywall is attached to framing.
Adaptable--builders can adapt ADA principles to suit any design and varying construction schedules.
Cost--materials and labor for standard designs should only cost a few hundred dollars.

ADA Disadvantages
New--although ADA is a proven technique, many building professionals and code officials are not familiar with its use.
Not a vapor barrier-- if required, a separate vapor barrier must be used with ADA. However, faced insulation batts, polyethylene plastic, or vapor retarder paint work well.
Requires thought--while ADA is simple, new construction techniques require careful planning to ensure that the air barrier remains continuous. However, ADA is often the most error-free and reliable air barrier for unique designs.
Requires care--gaskets and caulking can be damaged or removed by subcontractors when installing the drywall or utilities.

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Builders Guide to Energy Efficient Homes in Georgia

Infiltration ControlMaterials and Techniques

ADA Installation Techniques
Wood framed floors
s Seal the rim joist to minimize air currents around floor insulation. Also, seal rim joists for multi-story construction.
s For unvented crawl spaces or basements, seal beneath the sill plate.
s Seal the seams between pieces of subflooring with good quality adhesive.
Slab floors
s Seal expansion joints and penetrations with a concrete sealant such as one-part urethane caulk.
Exterior framed walls
s Seal between the bottom plate and subflooring with caulk or gaskets.
s Install ADA gaskets or caulk along the face of the bottom plate so that when drywall is installed it compresses the sealant to form an airtight seal against the framing. Some builders also caulk the drywall to the top plate to reduce leakage into the wall.
s Use drywall joint compound or caulk to seal the gap between drywall and electrical boxes. Install foam gaskets behind coverplates and caulk holes in boxes.
s Provide for a vapor retarder where recommended by using faced insulation batts, polyethylene, foil-backed drywall, or vapor retarder paint.
s Seal penetrations through the top and bottom plates for plumbing, wiring, and ducts. Local fire codes may require firestopping for leaks through top plates.

Partition walls
s Seal the drywall to the top plate of partition walls with unconditioned space above.
s Install gaskets or caulk on the face of the first stud in the partition wall. Sealant should extend from the bottom to the top of the stud to keep air in the outside wall from leaking inside.
s Seal the ductwork where it projects through partition walls.
s Seal penetrations through the top and bottom plates for plumbing, wiring, and ducts.
Windows and doors
s Seal drywall edges to either framing or jambs for windows and doors.
s Fill rough opening with spray foam sealant or suitable substitute.
s Caulk window and door trim to drywall with clear or paintable sealant.
Ceiling
s Follow standard finishing techniques to seal the junction between the ceiling and walls.
s When installing ceiling drywall do not damage ADA gaskets, especially in tight areas such as closets and hallways.
s Seal all penetrations in the ceiling for wiring, plumbing, ducts, attic access openings, and whole house fans.
s Seal all openings for chases and dropped soffits above kitchen cabinets and shower/ tub enclosures.
s Avoid recessed lights; where used, install airtight, IC-rated fixtures and caulk between fixtures and drywall.

Builders Guide to Energy Efficient Homes in Georgia

41

Infiltration ControlMaterials and Techniques

.igure 4-11 Between .loor Air Barrier
Bottom wall

Batt insulation in stud cavity
Continuous drywall system

Caulk between band joist and floor joists and plates after framing or Caulk or gasket between plates and band joists during framing

Floor joists Insulation at band joist

Polyethylene Air Barrier
Polyethylene is frequently used as a vapor barrier in homes. When installed correctly, it can also serve as an effective air barrier. To stop air leakage, the polyethylene (poly) must be sealed to the framing, and all penetrations and seams in the poly sealed as well. In practice, however, it is difficult to install poly in an airtight manner. Hence for most homes, the poly serves as only a vapor barrier--not an air barrier. Poly is not recommended for homes with predominately cooling climates, such as south Georgia.
Poly Advantages
Air/vapor barrier--if installed correctly, poly can serve as both an air and vapor retarder.
Availability--poly has been used for years in homes as a vapor diffusion barrier and is readily available in local building supply houses.
Installation--poly requires no special tools and can be installed in large sheets with relatively few joints. Standard 4-mil poly tears easily so most builders use 6-mil or stronger. Tears can be repaired with approved tapes. Special reinforced polyethylene products resist tearing and degradation by sunlight.

Cost--materials and labor for completely air sealing standard home designs should only cost a few hundred dollars.
Poly Disadvantages
Tears-- lightweight poly is easily torn.
Sealing penetrations and seams-- it can be difficult to seal poly to plumbing, wiring, and ducts; between overlapped seams; and at the junctions between floors, walls and ceilings. Many standard caulks do not provide an effective, long-term seal, so select products with 30 to 50-year guarantees.
Prevents use of interior finish adhesives-- poly covers the face of studs and joists, so the interior finish material cannot be glued to the framing.
Bulges--when installed, the poly can bunch or have bulges which may cause the interior finish material to bow.
Weatherability--standard polyethylene is degraded by ultraviolet light, so it must not be exposed to sunlight. More durable products must usually be special ordered and are more expensive.

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Builders Guide to Energy Efficient Homes in Georgia

Infiltration ControlMaterials and Techniques

Scheduling-- poly must be installed after the wall insulation and all utilities are in place. If left exposed during construction, poly is likely to be torn or damaged by sunlight.
Poly Installation Techniques
Seal all holes and penetrations as described in the ADA procedures.
Wood framed floors
s Most builders prefer to glue the subfloor to the floor joists so poly cannot be used between these materials. Instead, seal joints in the subflooring with caulking or quality adhesive, seal all penetrations between conditioned floors, and provide an effective seal at the band joist.
Slab floors
s Poly used beneath a slab floor helps reduce the movement of moisture and soil gases migrating upward through seams and cracks in the slab.
.igure 4-12 Sealing Polyethylene Sheets

Exterior framed walls
s Staple poly at studs to the interior surface of the exterior wall studs and plates after all utilities are roughed in and sealed, and insulation is installed.
s Overlap the ends of separate sheets at least one stud space. Staple the sheets over a framing member, and caulk or tape the seams.
s Caulk or tape poly to electrical boxes, plumbing, and registers.
s Pleat the poly at the corners so that drywall can fit tightly.
Partition walls
s Seal the poly to the partition wall studs or drywall nailing surface.
s Ceiling poly must be sealed to the partition wall top plates to create a continuous air barrier.
Windows and doors
s Caulk and staple the poly covering the wall directly to the window or door jamb, or attach a separate piece of poly to a window or door prior to installation, then seal this piece to the poly sheet covering the wall.

Sealant

Top plate

.igure 4-13 Polyethylene Window Seal

Stud
6 mil polyethylene
Sealant on studs where poly overlaps
Overlap polyethylene one stud cavity; staple at 4" - 6" spacing
Builders Guide to Energy Efficient Homes in Georgia

Wall vapor barrier sealed directly to window with
sealant and staples
43

Infiltration ControlMaterials and Techniques
Ceiling
s Poly can be used as a ceiling air barrier if stapled to the room surface of the ceiling joists.
s Ceiling poly must be sealed to the exterior wall poly to create a continuous air barrier.
s Ceiling poly must be sealed to the partition wall top plate.
s All penetrations in the ceiling poly must be sealed.
Housewraps
Housewraps serve as exterior air barriers and help reduce air leakage through outside walls. Most products block only air leakage, not vapor diffusion, so they are not vapor barriers.
Typical products are rolled sheet materials that can be stapled and sealed to the wall between the sheathing and exterior finish material. For best performance, a housewrap must be sealed with caulk or tape at the top and bottom of the wall and around any openings, such as for windows, doors, and utility penetrations.
A housewrap can help reduce air leakage through exterior walls, but by itself is not a continuous air barrier for the entire envelope, and hence is not a substitute for the ADA system. Housewraps, recommended primarily as further insurance against air leakage and because they block liquid water penetration, can help protect the building from moisture damage.
In some instances, the exterior sheathing may be used as an outside air barrier. Careful sealing of all seams and penetrations is required.

.igure 4-14 Housewrap installation details
.igure 4-15 Exterior air sealing of sheathing

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Builders Guide to Energy Efficient Homes in Georgia

Insulation Materials and Techniques

5. Insulation Materials and Techniques

An energy efficient building envelope contains
both a thermal barrier and an air barrier. The key to an effective thermal barrier is proper installation of quality insulation products. A house should have a continuous layer of insulation around the entire building envelope. Studies show that improper installation can cut performance by 20% or more. While some types of insulation offer reduced air infiltration, most do not, so always include an air barrier (see Chapter 4).

.igure 5-1 Insulating the Building Envelope
Minimum R-values

R-30 attic

R-19 to R-30 knee walls

R-16 walls

R-19 floors

R-1.7 windows

R-10 below-grade foundation wall

R-5 slab

Insulation Materials
The wide variety of insulation materials makes it difficult to determine which products and techniques are the most cost effective.
s Fiberglass and mineral wool products come in batt, roll and loose-fill form, as well as a highdensity board material. Many manufacturers use recycled glass in the production process. Fiberglass is used for insulating virtually every building component--from foundation walls to attics to ductwork.
s Cellulose insulation, made from recycled newsprint, comes primarily in loose-fill form. Cellulose batt insulation has also been introduced in the marketplace. Loose-fill cellulose is used for insulating attics and can be used for walls and floors when installed with a binder or netting. Because of its high density, cellulose has the advantage of helping stop air leaks in addition to providing insulation value.
s Rock wool insulation is mainly available as a loose-fill product. It is fireproof and many manufacturers use recycled materials in the production process.
s Expanded polystyrene (EPS), often known as beadboard, is a foam product made from molded beads of plastic. While it has the lowest Rvalue per inch of the foam products, it is also the lowest in price. EPS is used in many alternative building products discussed in this chapter, including foam foundation forms and structural insulated panels.

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45

Insulation Materials and Techniques

Table 5-1 Batt Insulation Characteristics

Thickness (inches)
3-1/2 3-5/8 3-1/2 6 to 6-1/4 5-1/4 8 to 8-1/2
8 9-1/2 to 9-3/4
12

R-value
11 13 15 19 21 25 30 30 38

Cost (/sq.ft.)
12-16 15-20 25-31 19-26 24-30 27-35 34-38 30-34 40-45

This chart is for comparison only. Determine actual thickness, R-value, and cost from manufacturer or local building supply.

INSULATION & THE ENVIRONMENT
There has been considerable study and debate about potential negative environmental and health impacts of insulation products. These concerns range from detrimental health effects for the installer to depletion of the earth's ozone layer.
Fiberglass and mineral wool--concerns about impacts on health from breathing in fibers - no universal proof as yet accepted.
Cellulose--concerns about the flammability, but the fire retardant chemical added to cellulose, along with its greater density, may provide greater fire safety than other insulation products.
Foam products and ozone--for years, many foam products contained CFC's, which are quite detrimental to the earth's ozone layer. The CFC's were the blowing agent which helped create the lightweight foams. Current blowing agents are:
s Expanded polystyrene--pentane, which has no impact on ozone layer, but may increase potential for smog formation.
s Extruded polystyrene, polyisocyanurate and polyurethane--use primarily HCFC's which are 90% less harmful to the ozone layer than CFC's. Some companies are moving to non-HCFC blowing agents.
s Open-cell polyurethane-- uses carbon dioxide, which is much less detrimental than other blowing agents.
For additional information about these and other insulation materials, see Table 5-2.

s Extruded polystyrene (XPS), also a foam product, is a homogenous polystyrene produced primarily by three manufactures with characteristic colors of blue, pink, and green.
s Polyisocyanurate and polyurethane are insulating foams with some of the highest available Rvalues per inch. They are not designed for use below grade, unlike the other foam insulation products.
s Open-cell polyurethane foam, used primarily to seal air leaks and provide an insulating layer.
s Aerated concrete, including lightweight, autoclaved (processed at high temperature) concrete, can provide a combination of moderate R-values and thermal mass for floors, walls, and ceilings in addition to structural framing.
Insulation Strategies
Commonly used fiberglass and cellulose products are the most economical, while foam products should be used more judiciously. Builders should use fiberglass, rockwool, or cellulose insulation in attics, walls, and floors. In attics loose-fill products are usually less expensive than batts or blankets. Blown cellulose is more dense than fiberglass or rockwool, which helps it stop air leaks.
.oam insulation strategies
Foam products are primarily economical when they can be applied in thin layers as part of a structural system or to help seal air leaks. Examples include:
s Foundation wall or slab insulation
s Exterior sheathing over wall framing
s Forms in which concrete can be poured
s As part of a structural insulated panel for building walls
s Spray-applied foam insulation
Critical guidelines
When installing any insulating material, the following guidelines are critical for optimum performance:
s Seal all air leaks between conditioned and unconditioned areas.

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Builders Guide to Energy Efficient Homes in Georgia

Insulation Materials and Techniques

Table 5-2 , Comparison of Insulation Materials (Environmental Characteristics, Health Impacts, and Typical Costs*)

Type of Insulation

Installation Method(s)

.iber Insulation

R-Value per inch (RSI/m) Raw Materials

Pollution from Manufacture IAQ impacts

Comments

Typical Cost ($/sq ft per R-value

Cellulose

loose fill, wetspray, dense pack, stabilized

3.0 - 3.7 newspaper, borates, (21 - 26) ammonium sulfate

Negligable

.iberglass

batts, loose fill, 2.2 -4.0 stabilized, rigid (15 - 28) board

silica, sand, limestone, boron, P. resin, cullet

Air pollution from energy use

Mineral wool

loose fill, batts

Perlite

loose fill

.oam Insulation and sheathing
Expandend polystyrene

rigid boards

Extruded polystyrene

rigid boards

Polyisocyanura- foil-faced rigid

te

boards

Phenollc

foil-faced rigid boards

Polyurethane

sprayed-in

Open cell Polyurethane

sprayed-in

2.8 - 3.7 (19 - 26) 2.5 - 3.3 (17 - 23)
3.6 - 4.4 (25 - 31)
5.0 (35)
5.6 - 7.7 (39 - 53)
8.0 (55)
5.6 - 6.8 (40 - 47)
4.3 (30)

steel slag, P. natural rock Air pollution from energy use

volcanic rock

Negligable

fossil fuels, pentane fossil fuels, HC.C-142b fossil fuels, HC.C-141b fossil fuels, HC.C-141b fossil fuels, HC.C-141b fossil fuels

Pentane emissions contribute to smog
Ozone depletion, global warming, energy use
Ozone depletion, global warming, energy use
Ozone depletion, global warming, energy use
Ozone depletion, global warming, energy use
Negligable

.iberboard sheathing
O.S.B. sheathing

rigid boards

2.6

rigid boards

1.3

sawmill waste, organic

Dryer

by-products, asphalt, wax emissions

Aspen or thinnings from commercial forests, phenol formel or isopropane, wax

Blue haze, particulates

.ibers and chemicals can be irrit ants, should be isolated from interior space
.ibers and chemicals can be irritants, should be isolated from interior space
see fiberglass

High recycled content, very low embodied energy

.011 - .016

New Miraflex fiber has no binder

batts: .019 .028 loose fill: .015 - .018

see fiberglass

NA

Concern only for those with chemical sensitivities

Primary nonHC.C foam board

.063 - .084

Concern only for those with chemical sensitivities

Only Amofoam-RCY has recycled content

.075 - .091

Concern only for those with chemical sensitivities

One non-HC.C based product is available

.061 - .075

Concern only for

Not currently NA

those with chemical manufactured

sensitivities

in U.S.

Concern only for those with chemical sensitivities

see polyisocyanurate

Unknown, appaears to be very safe
NA

Doesn't harden, good air sealing

NA .082 - .136

NA

.337 - .571

* not including installation
Source: Adapted with permission from Environmental Building News. For subscription information contact: Environmental Building News, 122 Birge St., Suite 30, Brattleboro, VT 05301 (USA). E-mail: ebn:@ebuild.com. Web site: www.ebuild.com.

Builders Guide to Energy Efficient Homes in Georgia

47

Insulation Materials and Techniques

s Obtain complete coverage of the insulation. s Minimize air leakage through the material. s Avoid compressing insulation. s Avoid lofting (installing too much air) in loose-
fill products.
.oundation Insulation
Slab-on-Grade Insulation
In many homes in Georgia, the bottom heated floor is a concrete slab-on-grade, meaning that a slab situated near ground level serves as the floor itself. Uninsulated slabs lose considerable heat in winter through their perimeter edges, even as far south as Albany.
Termite problems in slab insulation
While slab insulation reduces energy bills, its use is questioned in the Southeast because termites can burrow undetected through slab insulation to gain access to the wood framing above. The industry is working on solutions to the termite problem, but in the meantime, check with pest control companies to ensure termite contracts are valid for insulated perimeter slabs.
The Georgia Energy Code prohibits foam plastic within 6 inches of grade, instead allowing builders to substitute extra attic insulation and other measures for slab insulation. Unfortunately, any uninsulated portion

of the building envelope will increase energy bills and may create comfort problems. To avoid this, insulate slabs with non-plastic insulation (such as rigid fiberglass) or use a termite-resistant approach and obtain approval by the local inspector and a reputable termite company. Keep in mind these exceptions to the prohibition of foam plastic below grade:
s When approved protective membranes are provided that separate the foam plastic from the soil.
s Foam filled doors.
s Interior of basement walls.
Preventing termite problems is a key goal of any building, especially where a visual inspection of the foundation is not possible. Among the important preventive measures are:
s Good drainage--slope soil away from home and install foundation drains.
s Remove organic matter--remove all wood from around the foundation before backfilling.
s Direct moisture away from the home--use well maintained gutters and downspouts that connect to a drainage system.
s Provide continuous termite shields--protect wooden sill plate and other framing members. The sill plate should be made of pressure-treated lumber.
s Treat soil--or use an approved termite monitoring system.

Type of Treatment

Table 5-3 Economics of Slab .loor Insulation*

Incremental Energy Savings
($/yr)

Incremental Installed Costs ($)

1-inch perimeter insulation 2-inch perimeter insulation 2-inch perimeter insulation with 1-inch under floor of rooms on south side

70 90 n/a**

260 - 737 354 - 831 880 - 1,330

Annual Rate of Return
16 - 37% 18 - 36%
n/a

Incremental Mortgage Costs ($/yr)
32 - 91 44 - 103
n/a

*Shows savings in Atlanta versus no slab insulation. Ranges reflect different techniques for finishing exposed edges of slab. The insulation should always be rated for below-grade applications. Estimates are for an 1,800-square-foot slab.
**The energy savings for these options are difficult to predict accurately.

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Builders Guide to Energy Efficient Homes in Georgia

Insulation Materials and Techniques

SLAB INSULATION DETAILING
Detailing perimeter slab insulation should be planned carefully to prevent both aesthetic and moisture problems. The goals of detailing work are to blend foundation exterior finish with framed wall finish, prevent moisture problems, and create at least 2 feet of continuous perimeter insulation. Once again, make certain your termite contract covers homes with slab insulation.

.igure 5-2 Exterior Insulation with Termite Resistant Membrane

.igure 5-3 Interior L-shaped Insulation with Termite Resis-
tant Membrane

Drywall

Baseboard

Foam insulation

Insulated

sheathing

Sill gasket membrane

(also serves as capillary break)

Rigid insulation encapsulated or covered with membrane to
;y;y;y;y;y;y;y;y protect from
termites and
;;;;yyyy;;;;yyyy;;;;yyyy;;;;yyyy;;;;yyyy;;;;yyyy;;;;yyyy;;;;yyyy exterior damage

;;;yyy;;;;;yyyyy;;;;;yyyyy;;;;;yyyyyMons;;;;;yyyyyolalibGbtahrasi;;;yyycevel ;;;;;yyyyy6Gmbraailsvpeeolly

provides thermal break for slab
functions as an expansion joint
6mil poly
Gravel base
Non-monolithic slab

Carpet tack attached to slab

yyy;;;yy;y;;;;yy;;yyy;yy;y;;yy;y;;y;;yy;;y;yy;yy;y;;yyy;;;;yy;;yy;y;y;yy;;yyyy;;;;yyyy;;;;yyyy;;;;yyyy;;;;y;yyyy;;;;y;yyyy;;;;

Insulated sheathing
Sill gasket membrane (capillary break)
Metal termite flashing
Interior L-shaped insulation with termite resistant membrane

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49

Insulation Materials and Techniques

.oundation Wall Insulation
Foundation walls and other masonry walls are usually built of concrete block or poured concrete. Insulating foundation walls is more difficult than framed walls as there is no convenient cavity into which mineral wool batts can fit.
Insulating concrete block cores

.igure 5-5 Exterior .oam Insulation
(R-11 to R-12 overall)
Foundation wall

Builders can insulate the interior cores of concrete block walls with insulation such as:
Vermiculite-R-2.1 per inch
Polystyrene inserts or beads - R-4.0 to 5.0 per inch
Urethane foam-R-7.2 per inch
Unfortunately, the substantial thermal bridging in the concrete connections between cores continues to depreciate the overall R-value. This approach is only a partial solution to providing a quality, well insulating wall.

.igure 5-4 Insulating Concrete Block Cores
(R-4 to R-6 overall)

Loose fill vermiculite or

polystyrene beads

R-13

R-11

2-Inch, R-10 rigid insulation (continuous--prevents thermal bridging but must be 6" above grade if foam plastic)

Waterproofing

Interior foam wall insulation
Foam insulation can be installed on the interior of foundation walls; however, it must be covered with a material that resists damage and meets local fire code requirements. Half-inch drywall will typically comply, but furring strips will need to be installed as nailing surfaces. Furring strips are usually installed between sheets of foam insulation; however, to avoid the direct, uninsulated thermal bridge between the concrete wall and the furring strips, a continuous layer of foam should be installed underneath or on top (preferred) of the nailing strips.

R-2
Top view Exterior rigid fiberglass or foam insulation

.igure 5-6 Interior .oam Wall Insulation
(R-10 to R-14 overall)

Foundation wall

1 x 4 furring strips

1/2" Drywall

Rigid insulation is more expensive than mineral wool or cellulose; however, its rigidity is a major advantage. It can be placed directly over a foundation wall prior to backfilling and yield excellent insulating value. In addition, the exterior insulation will help protect waterproofing and will allow the block or concrete wall to provide thermal mass in winter and summer. However, it is difficult and expensive to obtain R-values as high as in framed walls.

Waterproofing 1- to 2-inch foam insulation

R-8 to 13
R-11 to 15

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Builders Guide to Energy Efficient Homes in Georgia

Insulation Materials and Techniques

Interior framed wall

Lightweight concrete products

In some cases, designers will specify a framed wall on the interior of a masonry wall. Standard framed wall insulation and air sealing practice can then be applied.

.igure 5-7 Interior .ramed Wall (R-11 to R-13 overall)
R-13 Batt insulation

2 X 4 Stud

Lightweight, aerated autoclaved concrete is an alternative wall system. The aerated concrete, which can be shipped as either blocks or panels, combines elevated R-values (compared to standard concrete) with thermal mass.
.igure 5-9 Lightweight Concrete Products (R-1.1 per inch plus mass effect)

Waterproofing

8-inch wall nominally R-9; equivalent to higher R-value because of thermal mass effect

Concrete block

1/2" Drywall

;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yyyy;;;;yy;yy;;;yy;yy;;;yy;yy;;y;yy;;yy;;y

Insulated Concrete .oundation systems

Permanent wood foundations

Polystyrene or polyurethane foam can be used as formwork for poured or sprayed structural concrete. Many of these systems can be economically attractive in areas with substantial heating and cooling requirements.

.igure 5-8 IC.s System (R-17 to R-24 overall)

Poured concrete

Rebar

;;yy;;yy;y;y;y;y;;yy;;;;yyyy;;;;yyyy;;yy;;;yyy;;yy;;;yyy;;yy;;;yyy;;;;;;;;;yyyyyyyyy;y;;;yyy;;;;;;;;;yyyyyyyyy;y;;;yyy;;;;;;;;;yyyyyyyyy;;;;yyyy;;;;;;;;;yyyyyyyyy

Plastic or metal furring

Foam block--

strips used for attaching

R-16 to 23

finishing materials

Wood foundations use pressure-treated (P.T.) plywood and framing to create a non-masonry foundation wall. These systems can be installed without concrete footers. The framed walls can be filled with mineral wool insulation, and the exterior, once waterproofed, can be covered with a drainage plane material. Builders must make certain to install effective drainage systems when using pressure-treated walls below grade to increase the longevity of the system.
.igure 5-10 Permanent Wood .oundations
(R-12 to R-22 overall)

Waterproofing
DpirpPfair.niTang.masgiinellgpla;;;;;yyyyyte;;;;;;;;;;yyyyyyyyyy;;;yyya;;;;;;;;;;yyyyyyyyyy;;;yyynd;;;;yyyy;;;;;;yyyyyy;;;yyy;;;;yyyy;;;;;;yyyyyy;;;yyy;;;;yyyy;;;;;;yyyyyy;;;;yyyy;;;;;;yyyyyy;;;;;;;;;;yyyyyyyyyy;;;;;;;;;;yyyyyyyyyy;;;;;;;;;;yyyyyyyyyy;;;;;;;;;;yyyyyyyyyy;;;;;;;;;;yyyyyyyyyy;;;;;;;;;;yyyyyyyyyy;;;;;;;;;;yyyyyyyyyy;;;;;;;;;;yyyyyyyyyy;;;;;;;;;;yyyyyyyyyy

P.T. plywood
R-13 to 21 insulation
Sealant

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51

Insulation Materials and Techniques

FOAM FORM FOUNDATION SYSTEMS

Foam insulation systems that serve as formwork for concrete foundation walls can save on materials and cut heat flow. Among these types of products are:
Foam blocks--Several companies manufacture foam blocks that can be installed quickly on the footings of a building. Once stacked, reinforced with rebar, and braced, they can be filled with concrete. Key considerations are:
s Bracing requirements--bracing the foam blocks before construction may outweigh any labor savings from the system. However some products require little bracing.
s Stepped foundations--make sure of the recommendations for stepping foundations--some systems have 12" high blocks or foam sections, while others are 16" high.
s Reinforcing--follow the manufacturer's recommendations for placement of rebar and other reinforcing materials.
s Concrete fill--make sure that the concrete ordered to fill the foam foundation system has sufficient slump to meet the manufacturer's requirements. These systems have been subject to frequent blowouts when the installer did not fully comply with the manufacturer's specifications. A blow-out is when the foam or its support structure breaks and concrete pours out of the form.
s Termites--these systems may require approval by code inspection officials. Also, be sure to consult with a reputable termite contractor.
Spray-on systems--Concrete can be sprayed onto foam panels which are covered by a metal reinforcing grid, part of which is exposed. Structural concrete mixture is sprayed onto the exposed reinforcing metal. As with foam block systems, installers must follow manufacturer's recommendations carefully for a successful system.

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Foam panel/ snap tie systems--Some companies produce systems in which insulation panels are locked together with plastic snap ties. A space, typically eight inches, is created between the foam panels that is filled with concrete. As with foam block systems, installers must follow manufacturer's recommendations carefully for a successful system.

;;;;;yyyyy;;;;;yyyyy;;;;;yyyyy;;;;;yyyyy;;;;;yyyyy;;;;;yyyyy ;;;;;;;yyyyyyy;;;;;;;yyyyyyy

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Builders Guide to Energy Efficient Homes in Georgia

Insulation Materials and Techniques

.ramed .loor Insulation
Insulating Under .loors

.igure 5-11 Insulated Wood .ramed .loors

1

2

Most floors in conventional homes are constructed with 2x10 or 2x12 wood joists, wood I-beams, or

3

6

trusses over unconditioned crawl spaces or base-

ments. Generally, insulation is installed underneath

4

7

the subfloor between the framing members. To meet

the Georgia Energy Code most homes need R-13 to R-

5

19 floor insulation, depending on climatic zone.

8

Most builders use insulation batts with an attached

11

9

vapor barrier for insulating framed floors. The batts

should be installed flush against the subfloor to

eliminate any gaps which may serve as a passageway

for cold air between the insulation and floor. Special

rigid wire supports called "tiger teeth" hold the insu-

10

lation in place. The vapor barrier of the insulation

should face up toward the living area.

1. Bottom plate

Run wiring, plumbing, and ductwork below the bottom of the insulation so that a continuous layer can be installed. Be certain to insulate all plumbing and ductwork in unconditioned spaces such as crawl

2 Sealant 3. Exterior finish 4. Insulated sheathing 5. Band joist 6. Subfloor

spaces and unheated basements.

7. 6-inch insulation batt with vapor

barrier against subfloor

8. Wire support

9. Sill plate (pressure treated)

10. Foundation wall

11. Capillary break and termite shield

Table 5-4 Economics of .ramed .loor Insulation*

Type of Treatment

Incremental Energy Savings
($/yr)

Incremental Installed Costs ($)

Annual Rate of Return

Incremental Mortgage Cost ($/yr)

R-11 batt (compared to no insulation)

207

R-13 batt (compared to R-11)

9

R-19 batt (compared to R-11)

17

317

75%

29

42

27%

4

85

25%

8

*For a home in Atlanta with 1,056 square feet of framed floor over a crawl space or unheated basement.

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53

Insulation Materials and Techniques

Insulating Crawl Space Walls
For years, building professionals have assumed the optimal practice for insulating floors over unheated areas was to insulate underneath the floor. However, studies performed in Tennessee several years ago found that insulating the walls in well sealed crawl spaces and unconditioned basements can be an effective alternative to underfloor insulation. While the annual heating bills in the homes tested were 1 to 3% higher than those with underfloor insulation, the cooling bills dropped by approximately the same amount. Because the crawl space remains cool in summer, the home can conduct heat to the crawl space if there is no insulation under the floor.
Crawl space wall insulation requirements:
s Cover the earth floor with 6- to 10-mil polyethylene (recommended in all homes).

s In winter, close the foundation vents. (As the sidebar on crawl space ventilation describes, it may be better to close the vents in summer as well.)
s Furnaces or water heaters that are located in these areas and require outside air for combustion should have a direct inlet duct from the outside.
s A 1- or 2-inch gap should be left at the bottom of the insulation to serve as a termite inspection strip.
s Insulate the band joist area in addition to the foundation wall.
s The crawl space or basement should be made airtight.
s Review plans for the insulation with local building officials to ensure code compliance.

.igure 5-12 Insulated Crawl Space Walls

Interior foam

Interior batt

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7

1

6

;;;;;;;yyyyyyy;;;;;;;yyyyyyy2;;;;;;;yyyyyyy;;;;;;;yyyyyyy;;;;;yyyyy;;yy;;;;;;;yyyyyyy;y;;;;;yyyyy;y;;;;;;;yyyyyyy;;;;;;;yyyyyyy;y;;;;;yyyyy;y;y;;;;;yyyyy;y;y;;;;;yyyyy;y;;;;;;;yyyyyyy;;;;;;;yyyyyyy;;;;;;;yyyyyyy;;;;;;;yyyyyyy

3

;;;;;;;yyyyyyy;;;;;;;yyyyyyy;;;;;;;yyyyyyy;;;;;;;yyyyyyy;;;;;;;yyyyyyy;;;;;yyyyy;y;y;;;;;yyyyy;y;y;;;;;yyyyy;y;y;;;;;yyyyy;y;y;;;;;yyyyy;y;y

4 5

1. 1- to 2-inch extruded polystyrene 2. 6-inch gap above ground 3. Insulation batt for band joist 4. R-13 to R-19 Batt 5. 2-inch termite inspection strip 6. Continuous poly coverage 7. Capillary break and termite shield

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Builders Guide to Energy Efficient Homes in Georgia

Insulation Materials and Techniques

ARE FOUNDATION VENTS NECESSARY?

Considerable research has recently delved into the murky world of foundation insulation. Research in the Southeast is questioning venting crawl spaces. During summers, air conditioning often cools the floor framing and crawl spaces below the dewpoint temperature of outdoor air. Vapor barriers, such as polyethylene, installed over earth floors in crawl spaces, can virtually eliminate moisture migration from the soil below. In summer, crawl spaces become quite humid. Using warm or hot outdoor air to lower humidity is virtually impossible.
When outdoor air at 92oF 60% RH enters a crawl space at 72oF 90% RH, condensation occurs. Venting crawl spaces which have air conditioning ducts can be of particular concern. Often the ductwork is leaky and poorly insulated and creates a cold surface that causes moisture in the air to condense. In some cases water accumulating in duct insulation has become heavy enough to pull ductwork loose.

Given the poor ability of outdoor air to aid in dehumidifying crawl spaces in summer, and most builders' desire to avoid ventilation in winter in order to keep crawl spaces warmer, many building professionals feel that an unvented crawl space is the best option in homes with good exterior drainage systems. However, get approval from local code officials before omitting vents.
.igure 5-13 Relative Humidity (RH) and .oundation Vents

92 60% RH

72 100%

92 70% RH

Table 5-5 Economics of .oundation Insulation Systems*

Type of Treatment
Masonry Wall Filled concrete blocks Exterior R-10 foam insulation Exterior R-5 foam insulation Interior R-10 foam insulation Interior R-5 foam insulation Interior framed wall (R-13 insulation)

Net Energy Savings
($/yr)
7 30 20 30 20 30

Net Installed Costs ($)
50 300 170 270 140 400

Annual Rate of Return
18% 13% 15% 14% 18% 9%

Net Mortgage Costs ($/yr)
5 28 16 25 13 37

Alternatives (due to highly variable costs and energy savings, the economics of these options are not evaluated) Foam block wall Spray-on-foam form Foam panel with snap ties Lightweight concrete block Permanent wood foundation

* For 500 square feet of wall in Atlanta, Georgia; net savings or costs compared to an uninsulated concrete block wall.

Builders Guide to Energy Efficient Homes in Georgia

55

Insulation Materials and Techniques

Advantages of crawl space wall insulation
s Less insulation required (around 800 square feet for a 2,000 square-foot crawl space with 4-foot walls)
s Pipe insulation is not required (spaces should stay warmer in winter)
Disadvantages of crawl space wall insulation s The insulation may be damaged by rodents and other pests
s If the soil has high radon concentrations, a radon mitigation system will generally require ventilation of the crawl space to the exterior, which necessitates under floor insulation
s If the crawl space is leaky to the outside, the home will lose considerably more heat than standard homes with underfloor insulation
s Proper site drainage is essential to keep the crawl space dry

Wall Construction
Walls are the most complex component of the building envelope to provide adequate thermal insulation, air sealing, and moisture control. Throughout the United States, debates continue on optimal wall construction. Table 5-6 summarizes typical problems and solutions in walls framed with 2x4 studs.
2x4 Wall Insulation
To solve some of the energy and moisture problems in standard wall construction, builders should follow the steps shown in Chapter 1. Some of these steps involve preplanning, especially the first time these procedures are used. In addition to standard framing lumber and fasteners, the following materials will also be required during construction:
s Foam sheathing for insulating headers
s 1x4 or metal T-bracing for corner bracing
s R-13 batts for insulating areas during framing behind shower/tub enclosures and other hidden areas
s -inch drywall or other sheet material where needed for sealing behind shower-tub enclosures and other areas that cannot be reached after construction

Table 5-6 2x4 .ramed Wall Problems and Solutions

Problem
Small space available for insulation
Enclosed cavities are more prone to cause condensation, particularly when sheathing materials with low R-values are used
Presence of wiring, plumbing, ductwork, and framing members lessens potential R-value and provides pathways for air leakage

Solutions
Install continuous exterior foam sheathing and medium (R-13) to high (R-15) density cavity insulation
Install a continuous air barrier system and a vapor barrier if applicable. Use continuous foam sheathing
Locate mechanical systems in interior walls; avoid horizontal wiring runs through exterior walls; use air sealing insulation system

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Builders Guide to Energy Efficient Homes in Georgia

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s caulking or foam sealant for sealing areas that may be more difficult to seal later
Avoid side stapling
Walls are usually insulated with fiberglass batts having an attached vapor retarder facing. The facing material has a flange that is often stapled to the sides of the studs in order to leave the face of the studs bare so that the drywall subcontractor can glue the interior finish to the wall studs. Gluing drywall requires fewer fasteners, thus saving on both installation and finishing costs. It can also reduce callbacks due to nail popping.
However, side stapling can compress the insulation and create an air space between the insulation and the interior finish, which allows cold air to circulate within the wall cavity. The combined effect of the compressed insulation and air circulation can reduce the effective insulating value of a R-13 batt to a value below R-10.
The insulation flange is designed to be stapled to the face of the studs at 12-inch intervals. Drywall cannot be glued over the flange, so it must be secured with fasteners. Face stapling the batt ensures that the insulation will completely fill the stud cavity and minimize air circulation. The facing has too many tears and seams to function as an adequate air barrier; however, it is an excellent vapor retarder.
An alternative to side stapling insulation batts with flanges is to use unfaced batts. They are slightly larger than the standard 16- or 24-inch stud spacing and rely on a friction-fit for support. Since unfaced batts are not stapled, they can often be installed in less time. In addition, it is easier to cut unfaced batts to fit around wiring, plumbing, and other obstructions in the walls.
Blown loose-fill insulation
Loose-fill cellulose, fiberglass, cotton, and rock wool insulation can also be used to insulate walls. It is installed with a blowing machine and held in place with a glue binder or netting. This technique can provide good insulation coverage in the stud cavities, however it is important that excess moisture in the binder be allowed to evaporate before the wall cavities are enclosed by a vapor barrier or interior finish.
Loose-fill materials with high densities, such as cellulose installed at around 3-4 pounds per cubic foot, are not only excellent insulators, but also seal air leaks. Fiberglass is less dense than cellulose and does not provide as much resistance to air circulation.

.igure 5-14 Insulating Walls With Batts Potential air movement
Compressed batt

Side stapled poor practice
Face stapled
Unfaced batts

Therefore, the additional benefits of air sealing must be considered when evaluating the economics of blown cellulose.
Neither unfaced insulation batts nor loose-fill products provides a vapor retarder. Many builders use polyethylene, foil-backed drywall, or a vapor retarder paint to reduce moisture diffusion through the interior finish material. A vapor retarder is not recommended for wet-spray installed insulation such as cellulose.

.igure 5-15 Blown Sidewall Insulation Options

Reinforced plastic
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off excess
;y;y;y;y ;y;y;y insulation

;;yy;y;y;y ;;;yyy;;;yyy;;;yyy Hosefor
moistening
;y insulation

Insulation hose from blowing machine

Builders Guide to Energy Efficient Homes in Georgia

57

Insulation Materials and Techniques
.igure 5-16 Blown .oam Insulation

.igure 5-17 Structural Insulated Panels (SIP)

Exterior siding

Drywall OSB panel

Extra foam over top and bottom plates seals air leaks
Blown foam insulation

1-Inch layer provides about R-7

OSB panel Metal framing

R-14 or greater foam

Some insulation contractors are now blowing polyurethane or icynene insulation into walls of new homes. This technique provides high R-values in relatively thin spaces and seals air leaks effectively. The economics of foam insulation should be examined carefully before deciding on its use.
Structural insulated panels
Another approach to wall construction is the use of structured insulated panels (SIP), also known as stress-skin panels. They consist of 4-inch or 6-inch thick foam panels onto which sheets of structural plywood or oriented strand board have been glued. They reduce labor costs, and because of the reduced framing in the wall, have higher R-values and less air leakage than standard walls.
SIPs are 4 feet wide and generally 8 to 12 feet long. There are a wide variety of manufacturers, each with its own method of attaching panels together. Procedures for installing windows, doors, wiring, and plumbing have been worked out by each manufacturer. In addition to their use as wall framing, SIPs can also form the structural roof of a building.
While homes built with SIPs may be more expensive than those with standard framed and insulated walls, research studies have shown SIP-built homes have higher average insulating values and are tighter. Thus, they can provide substantial energy savings.

Builders and designers are well aware of the increasing cost and decreasing quality of framing lumber. As a consequence, interest in alternative framing materials, such as metal framing, has grown. While metal framing offers advantages over wood such as consistency of dimensions, lack of warping, and resistance to moisture and insect problems, it has distinct disadvantages from an energy perspective.
Metal framing serves as an excellent conductor of heat. Homes framed with metal studs and plates usually have metal ceiling joists and rafters as well. Thus, the entire structure serves as a highly conductive thermal grid. Insulation placed between metal studs and joists is much less effective due to the extreme thermal bridging that occurs across the framing members.
The American Iron and Steel Institute is well aware of the challenges involved in building an energy efficient steel structure. In their publication Thermal Design Guide for Exterior Walls (Publication RG-9405), the Institute provides information on the thermal performance of steel-framed homes. Table 5-7 summarizes some of their findings.
There have been moisture-related problems in metal frame buildings in Georgia that do not use insulated sheathing on exterior walls. Metal studs cooled by the air conditioning system can cause outdoor air to condense leading to mildew streaks. In winter, studs covered by outside air can also cause streaking.

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Builders Guide to Energy Efficient Homes in Georgia

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STRUCTURAL INSULATED PANELS CONSTRUCTION
Wiring hole
1

Caulk or glue between OSB and framing
2

Wiring hole Sealant

s Install first panel on top of bottom plate--caulk in place
s Be careful to install panel plumb and level
s Continue installing panels, caulking all seams, and checking for plumb and level
s Install continuous top plate

Second top plate
3

Inset framing

s Install second top plate
s Run wiring
s Cut holes for windows if necessary
s Notch into foam using a special tool for inset framing around rough openings
s Install and caulk framing

Receptacles and switches notched into foam

Builders Guide to Energy Efficient Homes in Georgia

59

Insulation Materials and Techniques

Wall Sheathings
Many Georgia builders use 1/2 inch wood sheathing (R-0.6) or asphalt-impregnated sheathing, usually called blackboard (R-1.3), to cover the exterior walls of a building before installing the siding. Instead, use expanded polystyrene (R-2), extruded polystyrene (R-2.5 to 3), polyisocyanurate or polyurethane (R-3.4 to 3.6) foam insulated sheathing. (All R-values are per inch.)
Advantages of foam sheathing over wood or blackboard include:
s Saves energy
s Easier to cut and install
s Protects against condensation (Figure 5-20)
s Less expensive than plywood or oriented strand board
The recommended thickness of the sheathing is based on the desired R-value and the jamb design for windows and doors usually inch. Be certain that the sheathing completely covers the top plate and band

Table 5-7 Effective Steel Wall R-values

Cavity Insulation
11 11 11 13 13

Sheathing
2.5 5 10 2.5 5

Effective Overall R-value
9.5 13 18 10 14

joist at the floor. Most manufacturers offer sheathing products in 9- or 10-foot lengths to allow complete coverage of the wall. Once it is installed, patch all holes.
Because of its advantages over plywood, foam sheathing should be used continuously in combination with let-in bracing, which provides structural support.

.igure 5-18 .oam Sheathing Keeps Walls Warmer

R-13 Insulation

R-2.5 Foam sheathing

R-.5 Plywood sheathing

Sheathing temperature 38o

Sheathing temperature 43o

Inside = 68oF

Outside = 35oF

Water vapor will condense on cool surfaces below the 40oFdewpoint of air in the wall cavity. The foam sheathing is 5o warmer, thus helping prevent condensation.

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Builders Guide to Energy Efficient Homes in Georgia

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Table 5-8 Sheathing Costs*
Cost ($)

R-Value

1/2" oriented strand board 350

(OSB)

1/2" extruded polystyrene 383

1/2" blackboard

255

1/2" polyisocyanurate

383

1/2" beadboard (EPS)

255

0.60
2.5 1.3 3.5 - 3.7 2.0

* For an 1,824-square-foot home using 64 sheets of 4 x 8 material.

2x6 Wall Construction
There has been considerable interest in Georgia in the use of 2x6s for construction. In most code jurisdictions, 2x6s can be spaced on 24-inch centers, rather than 16-inch centers required for 2x4s. The advantages of using wider wall framing are:
s More space provides room for R-19 or R-21 wall insulation

s Thermal bridging across the studs is less of a penalty due to the higher R-value of 2x6s
s Less framing reduces labor costs
s There is more space for insulating around piping, wiring, and ductwork
Disadvantages of 2x6 framing include:
s Wider spacing may cause the interior finish or exterior siding to bow slightly between studs
s Window and door jambs must be wider and can add $12 to $15 per opening
s Walls with substantial window and door area may require almost as much framing as 2x4 walls and leave relatively little area for actual insulation
The economics of 2x6 wall insulation are affected by the number of windows in the wall, since each window opening adds extra studs and may require the purchase of a jamb extender. Table 5-9 shows a comparison of 2x4 versus 2x6 framing. Walls built with 2x6s having few windows provide a positive economic payback. However, in walls in which windows make up over 10% of the total area, the economics become more questionable.

Table 5-9 Analysis of 2x6 Walls*

Description of wall

Average R-values Extra Costs or Savings $

Wall Only Average with Costs ($)

30-year

Windows**

Savings ($)

no windows

2x4

15.37

same

2x6

19.94

same

18

60

2 windows (double-paned)

2x4

14.94

9.65

2x6

19.78

11.31

31

59

5 windows (double-paned)

2x4

14.20

6.20

2x6

19.15

6.82

103

57

* 400 sq.ft. with R-13, 2x4 construction versus R-19, 2x6 construction

**All windows double-glazed, 15 square feet

Net Savings
42
26
(-46)

Builders Guide to Energy Efficient Homes in Georgia

61

Insulation Materials and Techniques

2x4 stud

.igure 5-19 Let-In Bracing

Metal T-bracing saves on the labor cost of 1x4 let-in bracing

Saw kerf for T-brace

K-brace when window or door is near corner

1x4 let-in brace notched into wall studs

Table 5-10 Economics of Wall Insulation Systems*

Type of Treatment
2x4 Wall 1. R-11 batts, OSB corner sheathing,
R-2.6 insulated foam sheathing elsewhere (compared to a home with blackboard sheathing) 2. R-11 batts, R-2.6 sheathing, insulation detailing (compared to Case 1) 3. R-13 batts and treatment in Case 2 ( compared to Case 2) 4. R-15 batts and treatment in Case 2 (compared to Case 3) 5. R-11 batts, R-5.2 sheathing, insulation detailing (compared to Case 2) 2x6 Wall 6. R-19 batts, R-2.6 sheathing, insulation detailing (compared to Case 2) 7. R-21 batts, R-2.6 sheathing, insulation detailing

Incremental Incremental

Energy Savings Installed

($/yr)

Costs ($)

20

217

9

31

11

102

9

213

23

753

22

785

24

865

(compared to Case 2)

*For a home with 1,862 square feet of wall area located in Atlanta, Georgia

Annual Rate of Return 10.1%
36.0%
14.2% 3.4% 1.6%
minimal
minimal

Incremental Mortgage Costs ($/yr) 20
3
9 20 69
72
80

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Builders Guide to Energy Efficient Homes in Georgia

Insulation Materials and Techniques

Ceilings and Roofs
Attics over flat ceilings are usually the easiest part of a home's exterior envelope to insulate. They are accessible and have ample room for insulation. However, many homes use cathedral ceilings that provide little space for insulation. It is important to insulate both types of ceilings properly.

The combination of continuous ridge vents along the peak of the roof and continuous soffit vents at the eave provides the most effective ventilation. Ridge vents come in a variety of colors to match any roof. Some brands are made of plastic covered by cap shingles to hide the vent from view.
Powered attic ventilator problems

Attic Ventilation
In winter, properly designed roof vents expel moisture which could otherwise accumulate and deteriorate insulation or other building materials. In summer, ventilation reduces roof and ceiling temperatures, thus potentially saving on cooling costs and lengthening the life of the roof.
At present, several research studies are investigating whether attic ventilation is beneficial. For years, researchers have believed the cooling benefits of ventilating a well insulated attic are negligible. However, some experts are now questioning whether ventilation is even effective at moisture removal. Until the results of current research have been accepted, builders should follow local code requirements, which usually dictate attic ventilation.
Vent selection
If ventilating the roof, locate vents high along the roof ridge and low along the eave or soffit. Vents should provide air movement across the entire roof area. There are a wide variety of products available including ridge, gable, soffit, mushroom, and turbine vents.

Electrically powered roof ventilators can consume more electricity to operate than they save on air conditioning costs and are not recommended for most designs. Power vents can create negative pressures in the home which may have detrimental effects such as:
s Drawing air from the crawl space into the home
s Pulling pollutants such as radon and sewer gases into the home
s Backdrafting fireplaces and fuel-burning appliances

.igure 5-21 Pressure Problems Due to Powered
Attic Ventilators

Attic ventilation fan

When fan operates, attic pressure drops

.igure 5-20 Ridge and Soffit Vents

Air is drawn into attic causing house pressure to drop

Crawl space air is drawn into house

Builders Guide to Energy Efficient Homes in Georgia

63

Insulation Materials and Techniques

Guidelines for attic/roof ventilation
The amount of attic ventilation needed is determined by the size of the attic floor and the amount of moisture entering the attic. General guidelines are:
s 1 square foot of attic vent for each 150 square feet of attic floor area without a ceiling vapor retarder.
s 1 square foot of vent for each 300 square feet if there is a vapor retarder.
s The total vent area should be divided equally between high and low vents.

Table 5-11 Typical Attic Insulation Costs*
Flat Ceiling

R-19 Batt Insulation R-30 Batt Insulation

$371 540

R-19 Blown Insulation

264

R-30 Blown Insulation

360

R-38 Blown Insulation

443

*For a 1,056-square-foot attic

Attic .loor Insulation Techniques
Either loose-fill or batt insulation can be installed on an attic floor. Batts with attached vapor retarders should be installed with the backing next to the ceiling. As shown in Table 5-11, blowing loose-fill attic insulation is usually less expensive than installing batts or rolls. Most attics have either blown fiberglass, rock wool or cellulose.
Steps for installing loose-fill attic insulation:
1. Seal attic air leaks, as prescribed by fire and energy codes.
2. Follow manufacturers clearance requirements for heat-producing equipment found in an attic, such as flues or exhaust fans. Other blocking requirements may be mandated by local building codes. Use either metal flashing, plastic or card-

board baffles, or pieces of batt insulation for blocking. Attic blocking requirements are shown in the sidebar.
3. Use cardboard baffles, R-30 batts, or other baffle materials to preserve ventilation space at eave of roof for soffit vents.
4. Insulate the attic hatch or attic stair. There are foam boxes for providing a degree of insulation over a pull-down attic stairway.
5. Determine the attic insulation area; based on the spacing and size of the joists, use the chart on the insulation bag to determine the number of bags to install. Figure 5-13 shows a sample chart for cellulose insulation.

Table 5-12 Economics of Attic Insulation*

Type of Treatment
1. R-30 blown insulation (compared to R-19 blown insulation) 2. R-38 blown insulation (compared to Case 1)

Incremental Energy Savings
($/yr) 25
12

Incremental Installed Costs ($) 96
83

3. R-30 batts (compared to R-19 batts)

23

169

Annual Rate of Return 33.0%
18.0%
17.0%

Incremental Mortgage Costs ($/yr) 9
8
16

*For a home with a 1,056-square-foot attic area located in Atlanta, GA

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Builders Guide to Energy Efficient Homes in Georgia

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ATTIC BLOCKING REQUIREMENTS

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Recessed light

3-inch clearance on all sides, unless rated as Insulated Coverage (IC)

Doorbell transformer

Do not cover; no clearance on sides required

Masonry chimney

2-inch clearance

Metal chimney

2-inch clearance or follow manufacturer's recommendations

Kitchen/bath exhaust fan may require clearance

2-inch clearance around masonry chimney

Vent pipes from fuel-burning equipment

Follow manufacturer's recommendations

;;;;;;yyyyyy;;;;;;yyyyyy;;;;;;yyyyyy;;;;;;yyyyyy;;;;;;yyyyyy;;;;;;yyyyyy;;;;;;yyyyyy;;;;;;yyyyyy;;;;;;yyyyyy;;;;;;yyyyyy

Kitchen/bath exhaust Heat/light/ventilation Uncovered electric
Whole house fan

Duct to the outside; leave 3-inch clearance at mouth of blower if not ducted
3-inch clearance on all sides
Cover the box and insulate junction boxes over it. If it is left uncovered, leave a 3-inch clearance
Install blocking up to the fan housing; leave 3-inch clearance around fan motor

Put covers on all electric junction boxes and insulate over. If uncovered, maintain 3inch clearance

Attic access door

Block around the door if blowing in loose-fill insulation

*These are general guidelines. Follow specific manufacturer's recommendations.

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Insulation Materials and Techniques

R-value at 75oF R-40 R-32 R-24 R-19

Table 5-13 Blown Cellulose in Attics

2x6 Joists Spaced 24 Inches on Center

Minimum Thickness (in)
10.8 8.6 6.5 5.1

Minimum Weight Coverage per

(lb/ft2)

25-lb. bag (sq ft)

2.10

12

1.60

16

.98

21

.67

37

Bags per 1,000 sq ft
83 63 48 27

2x6 Joists Spaced 16 Inches on Center

Coverage per Bags per 25-lb bag (sq ft) 1,000 sq ft

13

77

18

56

23

43

41

24

6. Avoid fluffing the insulation (blowing with too much air) by using the proper air-to-insulation mixture in the blowing machine. A few insulation contractors have "fluffed" (added extra air to) loosefill insulation to give the impression of a high R-value. The insulation may be the proper depth, but if too few bags are installed, the R-values will be less than claimed.
7. Obtain complete coverage of the blown insulation at relatively even insulation depths. Use attic rulers to ensure uniform depth of insulation.
Steps for installing batt insulation
1. Seal attic air leaks, as prescribed by fire and energy codes.
2. Block around heat-producing devices, as described in Step 2 for Loose-fill Insulation.
3. Insulate the attic hatch or attic stair as described in Step 4 for Loose-fill Insulation.
4. Determine the attic insulation area; based on the spacing and size of the joists, order sufficient R-30 insulation for the flat attic floor. Choose batts that are tapered -- cut wider on top-- so that they cover the top of the ceiling joists. (Figure 5-24)

.igure 5-22 .ull Width Batts
Batts are cut wider on top-- they cover top of the ceiling joists

.igure 5-23 Insulating Under Attic .loors

2x4 spacer

Plywood floor

2x4 2x6

2x4 on edge allows for full insulation
Ceiling joist

Seal penetrations at ceiling

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Builders Guide to Energy Efficient Homes in Georgia

Insulation Materials and Techniques

.igure 5-24 Insulation Options for Eaves
Truss Roof
Problem Roof deck compresses insulation and blocks air flow from soffit vent
Solution--raised heel trusses Insulation not compressed; air flow path is open Wood-Framed Roof
Problem Roof compresses insulation at eave and blocks air flow from soffit vent
Solution--raised top plate Insulation not compressed; air flow path is open

5. When installing the batts, make certain they completely fill the joist cavities. Shake batts to ensure proper loft. If the joist spacing is uneven, patch gaps in the insulation with scrap pieces. Try not to compress the insulation with wiring, plumbing or ductwork. In general, obtain complete coverage of full-thickness, non-compressed insulation.
6. Attic storage areas can pose a problem. If the ceiling joists are shallower than the depth of the insulation (generally less than 2x10s), raise the finished floor using 2x4s or other spacing lumber. Install the batts before nailing the storage floor in place. (Figure 5-25)
Increasing the roof height at the eave
One problem area in many standard roof designs is at the eave, where there is not enough room for full R-30 insulation without preventing air flow from the soffit vent or compressing the insulation, which reduces its R-value. Figure 5-26 shows several solutions to this problem. If using a truss roof, purchase raised heel trusses that form horizontal overhangs. They should provide adequate clearance for both ventilation and insulation.
In stick-built roofs, where rafters and ceiling joists are cut and installed on the construction site, an additional top plate that lays across the top of the ceiling joists at the eave will prevent compression of the attic insulation. The rafters sitting on this raised top plate allow for both insulation and ventilation.
Problems with recessed lights
Standard recessed fixtures require a clearance of several inches between the sides of the lamp's housing and the attic insulation. In addition, insulation cannot be placed over the fixture. Even worse, recessed lights leak considerable air between attics and the home.
IC-rated fixtures have a heat sensor switch which allows the fixture to be covered with insulation. However, these units also leak air. Airtight, IC-rated fixtures are now required by the Georgia Energy Code, which has specific air tightness requirements. There are alternatives to recessed lights, including surface-mounted ceiling fixtures and track lighting.

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67

Insulation Materials and Techniques

Cathedral Ceiling Insulation Techniques
Cathedral ceilings are a special case because of the limited space for insulation and ventilation within the depth of the rafter. Fitting in a 10-inch batt (R-30) and still providing ventilation is impossible with a 2x6 or 2x8 rafter.
The Georgia Energy Code may allow R-19 cathedral ceiling insulation for some house designs, depending on the climatic zone. For most areas of the state, R-25 to R-30 insulation is recommended. Builders may find some installation cost savings using R-25 batts; however, they are about the same thickness as high density R-30 batts and would follow the same construction practices as outlined below.
Building R-30 cathedral ceilings
Cathedral ceilings built with 2x12 rafters can be insulated with standard R-30 batts and still have plenty of space for ventilation. Some builders use a vent baffle between the insulation and roof decking to ensure that the ventilation channel is maintained.
According to ASHRAE Fundamentals 1997, roof ventilation may not be necessary: "Because vents in cathedral ceilings are less likely to provide effective ventilation, potential beneficial effects on moisture conditions, shingle life, and energy conservation during the cooling season are very limited. Therefore, the benefits of vents in cathedral ceilings do not clearly outweigh their potential drawbacks and should not be required in cases where adding vents is particularly difficult or undesirable." Check with the local inspector to see if space for ventilation is required.
If 2x12s are not required structurally, most builders find it cheaper to construct cathedral ceilings with 2x10 rafters and high-density R-30 batts, which are 8 inches thick.
Some contractors wish to avoid the higher cost of 2x10 lumber and use 2x8 rafters. These roofs are usually insulated with R-19 batts. However, by using lower grade 2x10 lumber, such as a HemFir product, the additional costs may be avoided. In fact, the cost of a cathedral ceiling built with 2x10 HemFir may actually be less than one built with 2x8, #2 spruce or pine if the rafters can be spaced further apart. Another option is to lag 2x2s either in-line or perpendicular to the 2x8s to create additional space for insulation.

.igure 5-25 Choose Quality Recessed Lamps

Standard Recessed Lamp

Airtight, IC-Rated Recessed Lamp

Insulation clearance required

Can be fully insulated on sides and top

Airtight "can"

Substantial air leakage

Airtight seal to ceiling finish

Table 5-15 Cathedral Ceiling Insulation Options

Rafter

Batt

Typical Cost*

2x10

R-25

$1.50/ sq ft

2x10

R-30 High Density

$1.65/sq ft

2x12 R-30 Regular Density

$1.95/sq ft

* Typical labor and materials cost for rafter framing and insulation.

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Table 5-14 Economics of Cathedral Ceiling Insulation*

Type of Treatment

Net Energy Savings
($/yr)

1. 2x12 rafters** and R-30 batts

16

2. 2x8 rafters, R-19 batts, and

12

1-inch rigid insulation on interior

face of rafters

3. 2x10 rafters and R-25 batts

10

4. 2x10 rafters and high-density

16

R-30 batts

5. Cathedral ceiling with 4-inch R-27

13

foam insulation and exposed beams

Net Installed Costs ($)
276 307

Annual Rate of Return
6.0% minimal

Net Mortgage Costs ($/yr)
25 28

153 202
1,000 or more

8.0% 9.0%
minimal

14 19
92 or more

*For a home with 614 square feet of cathedral ceiling area located in Atlanta, Georgia; compared to a cathedral ceiling space with R19 insulation.
** Rafters are deeper than insulation to allow a ventilation space.

In framing with 2x6 and 2x8 rafters, higher insulating values can be obtained by installing rigid foam insulation under the rafters. However, foam can be expensive and using thicker rafters may be substantially less costly. Note that the rigid foam insulation must be covered with a fire-rated material when used on the interior of the building. Half-inch drywall usually meets the requirement. Check with local building codes if unsure.
Scissor trusses
Scissor trusses are another cathedral ceiling framing option. Make certain they provide adequate room for both R-30 insulation and ventilation, especially at their ends, which form the eave section of the roof.

Difficulties with exposed rafters
A cathedral ceiling with exposed rafters or roof decking is difficult and expensive to insulate well. Often, foam insulation panels are used over the attic deck as shown in Figure 5-26. However, to achieve R-30, 4 to 7 inches of foam insulation, which typically cost $1 to $3 per square foot, are needed. Ventilation is also a problem and some shingle manufacturers do not offer product warranties unless the outer roof decking is ventilated.
In homes where exposed rafters are desired, it may be more economical to build a standard, energy efficient cathedral ceiling, and then add exposed decorative beams underneath. Note that homes having tongue-and-groove ceilings can experience substantially more air leakage than solid, drywall ceilings. Install a continuous air barrier, sealed to the walls, above the tongue-and-groove roof deck.

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69

Insulation Materials and Techniques

.igure 5-26 Cathedral Ceiling - Exterior Roof Insulation

Outer roof decking

Exposed beam

Radiant heat barriers
Radiant heat barriers (RHB) are reflective materials that can reduce summer heat gain by the insulation and building materials in attics and walls. RHBs work two ways: first, they reflect thermal radiation well and second, they emit (give off) very little heat. RHBs should always face a vented airspace and be installed to prevent dust build-up. They are usually attached to the underside of the rafter or truss top chord or to the underside of the roof decking and may be cost effective in hot climates.

3- to 4-Inch rigid insulation

Exposed ceiling decking (drywall or tongue-ingroove interior finish)

.igure 5-27 Radiant Heat Barrier

Ventilation channel

Radiant barrier -

Roof

shiny side down

R-30 high density insulation batt
2x10 rafter

Decorative beam
Continuous air barrier (such as sealed housewrap) installed between batt and tongue-in-groove interior finish

Radiant heat barriers lower attic temperatures and may be beneficial in reducing air conditioning requirements.

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Windows and Doors

6. Windows and Doors

Windows connect the interior of a house to the
outdoors, provide ventilation and daylighting, and are one of the key aesthetic elements. In passive solar homes, windows can provide a significant amount of heat for a house in the winter.
Windows and doors are often the architectural focal point of residential designs, yet they provide the lowest insulating value in the building envelope. Although recent developments in energy efficient products have markedly improved the efficiency of windows, they still represent one of the major energy liabilities in new construction.
The type, size, and location of windows greatly affect heating and cooling costs. Select good quality windows, but shop wisely for the best combination of price and performance. Many housebuilding budgets have been blown by spending thousands of additional dollars on premium windows with marginal energy savings. In general, if the windows are double-glazed, well-built and have good weatherstripping, they will serve you well. Even better, consider low-emissivity, gas-filled windows for additional energy savings as these are available at relatively low extra cost.
Typical costs for several types of windows are shown in Table 6-1. Well designed homes carefully consider window location and size. In summer, unshaded windows can double the costs of keeping a house cool. Year round, poorly designed windows can cause glare, fading of fabrics, and reduced comfort. Chapter 11 on passive solar design describes how to design windows to save even more energy.

WINDOW ANATOMY

Inside casing Foam sealant Jamb
Weatherstripping
Stool Apron

Flashing Outside casing
Parting stop Rail for upper sash
Meeting rail
Lower sash Rail Sill

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Windows and Doors

Windows

Goals of Efficient Windows

To understand new window technologies, it is helpful to understand how they lose and gain heat:
s Conduction though the glass and frame
s Convection across the air space in double- and triple-glazed units
s Air leakage around the sashes and the frame
s Radiant energy from the sun travels through the glazing

s High R-values--a minimum of R-1.7 which requires double-glazed glass
s Low air leakage rates--
less than .25 cfm per linear foot of sash opening for double-hung windows
less than .10 cfm per linear foot for casement, awning, and fixed windows
s Moderate to high transmission rates of visible light
s Low transmission rates of invisible radiation --ultraviolet and infrared light energy

20o out

.igure 6-1 Winter Heat Loss in a Double-glazed Window
Radiant heat flow to cool window surfaces

Conduction from glass to outside air
Conduction through metal channel

Convection current

65 o in
Metal spacer channel filled with desiccant

Wood frame conduction

95o out

.igure 6-2 Summer Heat Gain in a Double-glazed Window

Incoming sunlight Absorbed Reflected

105o
Convection current

Radiant heat
Absorbed
Transmitted solar gain (78%)

75o in

Conduction through metal channel
Wood frame conduction

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Windows and Doors

Type of Window

Table 6-1 Cost Comparison of Window Alternatives
Cost per Square Foot of Rough Opening ($)*

Builder's Quality

Premium Quality

Single-glazed: Double-hung wood

5

11 - 18

Double-glazed:
Double-hung--wood Double-hung--vinyl or aluminum clad Casement or awning--wood Casement or awning--aluminum or vinyl clad Sliding glass door--metal Sliding glass door--wood Fixed/hinged operable door combination

8 10 14 - 18 19 - 23 5 - 8 9 - 14 n/a

11 - 18 12 - 25 20 - 27 25 - 31 7 - 10 10 - 15 11 - 18

*Windows generally cost about $50 in labor to install. Sealed, double-glazed glass units cost about $2.50 per square foot not including labor and trim, which may run about $7 per square foot.

Few windows can meet all of these goals, but in the past several years, the window industry has unveiled an exciting array of higher efficiency products. The most notable developments include:
s Low-emissivity coatings, which hinder radiant heat flow.
s Inert gas fills, such as argon and krypton, that help deaden the air space between layers of glazing and thus increase the insulating values of the windows.
s Tighter weatherstripping systems to lower air leakage rates.
s Thermal breaks to reduce heat losses through highly conductive glazing systems and metal frames.
The Problem of Reporting Window Insulating Values
Window insulating values are typically reported in Uvalues--the inverse of R-values. Double-glazed products have R-values as high as 2.0, or U-values of about 0.50 (1/R = = 0.50). Single-glazed windows generally have R-values of 1.0 and thus have U-values of 1.0.

The National Fenestration Rating Council (NFRC) offers a voluntary testing program for window and door products. The NFRC reports an average whole window U-value and R-value. If windows used in your home are listed by the NFRC, they will include a label showing test data for your windows.
Occasionally, window R-values are reported as the insulating value through the glass surface alone. However, windows are made of more than just glass. They have a frame or sash, spacer strips, typically made of aluminum, that hold the sections of glass in a double-glazed window apart, and a jamb. The claimed R-value should reflect the overall insulating value of all of the components. New procedures are encouraging all manufacturers to report window R-values consistently and accurately.
For example, there are two companies which produce extremely efficient windows. Both have two outer glass panes and two inner layers of low-e coated film. In one case, all air spaces are filled with argon, providing an R-value of 7.8 for the glass. However, losses through the edges and frames lower the overall window R-value to 4.0. Another window is filled with air rather than argon yielding an R-value of 6.6 for the glass. Due to

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73

Windows and Doors

Table 6-2 Typical R-Values for Windows with Various .rame Types
Glazing System

Frame Type

Single Glass

Double Glass

All Glass Window

.91

2.04

Window with Wood Frame

1.06

1.79

Window with Metal Frame and

0.93

1.49

Thermal Break

Window with Metal Frame

0.77

1.15

and No Thermal Break

Note: Double and triple glass systems have 0.5" air spaces between the layers of glass.

Triple Glass
3.20 2.75 2.25
1.60

LOW - EMISSIVITY COATINGS

Low-e coatings are primarily designed to hinder radiant heat flow through multi-glazed windows. Some surfaces, such as flat black metal used on wood stoves, have high emissivities and radiate heat readily. However, other surfaces, such as shiny aluminum, have low emissivities and radiate little heat, even when at elevated temperatures.
Low-e coatings are usually composed of a layer of silver applied between two protective layers. The coatings have swept through the window industry. Several window companies rarely sell products without low-e layers applied.
Low-e windows have additional benefits:
s Screen ultraviolet radiation, which reduces fabric fading
s Increase the surface temperature of inside glass, which makes us feel warmer because we radiate less heat.
s Helps prevent condensation and frost formation

.igure 6-3 Low-e, Gas-.illed Windows
Winter Performance
Low-e layer on interior of inside pane reduces radiant heat loss
Heavier inert gas increases insulating value and reduces convection currents
Summer Performance
Radiant heat gain reflected outside
More incoming sunlight reflected
Convection current reduced by inert gas fill

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Windows and Doors

.igure 6-4 Sample N.RC Label

National Fenestration

Rating Council

Incorporated

AAA Window Company

Manufacturer stipulates that these ratings were determined in accordance with applicable NFRC procedures.

Energy Rating Factors

Ratings
Residential Nonresidential

Product Description

U-Factor
Determined in Accordance w ith NRFC 100.

0.4 0.48 Model 1000
Casement

Solar Heat Gain Coefficient
Determined in Accordance w ith NRFC 200.

0.65

0.66 Low-e = 0.2
0.5" gap

Visible Light Transmittance 0.71 0.71 Argonfilled

Determined in Accordance w ith NFRC 300 & 301

Air Leakage

0.1 0.1

Determined in Accordance w ith NFRC 400.

NFRC ratings are determined for a fixed set of environmental conditions and specific product sizes and may not be appropriate for directly determining seasonal energy performance. For additional information, contact:

.igure 6-5 Metal Window .rame With Thermal
Break
Metal frames for windows
Insulating thermal break

its unique edge system, which has thermal breaks made of nylon spacers with insulation in between, the overall window R-value is about 6.3-- 50% greater than that for the window with higher glass R-value. Future development in windows will concentrate on both glass technology and the balance of the window--edge, seals, and frames.
NFRC also has an approved procedure to determine air infiltration of other fenestration products. NFRC labels will also provide:
s Air leakage rates (AL)
s Solar Heat Gain Coefficient (SHGC)--the fraction of sunlight transmitted through the window
s Visible Transmission (VT)--the fraction of visible light that is transmitted

Thermal Breaks and Window Spacers
Thermal breaks in metal window frames are of particular importance. Metal is a very poor insulator--in fact, it is a conductor of heat. A thermal break separates inside and outside pieces of the window frame with an insulating material, thus improving Rvalues. Always specify windows with thermal breaks, listed as "T.I.M" (thermally improved metal) when purchasing metal windows.
Thus, when shopping for windows, find out the total R-value, not just that for the glass. Also, ask how the R-value was determined and whether any standard test procedure was used to derive it. It makes no sense to pay top dollar for a window that looks great on paper, but performs poorly in the real world.

75oF inside

.igure 6-6: Inside Window Temperatures in Cold Weather

20oF outside

33oF

54oF

64oF

70oF

Single-glazed

Double-glazed

Double-glazed with low-e coating and inert gas fill

Quad-paned with low-e coating and inert gas fill

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75

Windows and Doors

Guidelines for Comparing Window Properties in the Southeast Region
The Southeast Region is a cooling dominated climate to the south and a mixed climate requiring both heating and cooling to the north.

U-.actor

Heat Loss

The rate of heat loss is

indicated in terms of the 0F

70F

U-factor (U-value) of a win-

dow assembly. The insu-

lating value is indicated

by the R-value which is

the inverse of the U-value.

The lower the U-factor, the

greater a window's resistance to heat flow and the

better its insulating value.

Recommendation:

Both Heating and Cooling/North Georgia: Select windows with a U-factor of 0.40 or less. The larger the heating bill, the more important a low U-factor becomes.

Mostly Cooling/South Georgia: A low U-factor is useful during cold days when heating is needed. A low U-factor is also helpful during hot days when it is important to keep the heat out, but it is less important than SHGC in warm climates. Select windows with a U-factor lower than 0.75 and preferably lower than 0.60.

Solar Heat Gain Coefficient (SHGC)

Solar Heat Gain

The SHGC is the fraction of incident solar radiation admitted through a window. SHGC is expressed as a number between 0 and 1. The lower a window's solar heat gain coefficient, the less solar heat it transmits.
Recommendations:
Both Heating and Cooling/North Georgia: If there are significant air conditioning costs or summer over-

heating problems, look for SHGC values of 0.40 or less. For moderate air conditioning requirements, select windows with a SHGC of 0.55 or less. While windows with lower SHGC values reduce summer cooling and overheating, they also reduce free winter solar heat gain. Use a computer program such as RESFEN to understand heating and cooling trade-offs.
Mostly Cooling/South Georgia: A low SHGC is the most important window property in warm climates. Select windows with a SHGC less than 0.40.

Visible Transmittance Daylight
(VTglass and VTwindow)
The visible transmittance (VT) is an optical property that indicates the amount of visible light transmitted. VT is expressed as a number between 0 and 1. The higher the VT, the more daylight is transmitted. A high VT is desirable to maximize daylight.
Recommendation:
A window with VTglass above 0.70 (for the glass only) is desirable to maximize daylight and view. This translates into a VTwindow above 0.50 (for the total window including a wood or vinyl frame).

Air Leakage (AL)

Infiltration

Heat loss and gain occur by infiltration through cracks in the window assembly. AL is expressed in cubic feet of air passing through a square foot of window area. The lower the AL, the less air will pass through cracks in the window assembly. While many think that AL is extremely important, it is not as important as U-factor and SHGC.
Recommendation:
Select a window with an AL of 0.30 or below (units are CFM/sq ft).
Source: This section adapted with permission from the Efficient Windows Collaborative, Alliance to Save Energy, 1200 18th St., NW, Suite 900, Washington, DC 20036, http://www.efficientwindows.org.

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Windows and Doors

Comparing Window Performance in Atlanta
The annual energy performance figures shown here were generated using RESFEN for a typical 2000 sq. ft. house with 300 sq ft of window area (15% of floor area). The windows are equally distributed on all four sides of the house and include typical shading (interior shades, overhangs, trees and neighboring buildings). The heating system is a gas furnace with air conditioning for cooling. The figures are based on typical energy costs for this location (natural gas: $0.60/therm and electricity: $0.082/kWh). U-Factor, SHGC, and VT are for the total window including frame.

Case Studies

Properties Annual Energy Use

Window 1 Single Glazing Clear Glass Aluminum Frame

U = 1.25 SHGC = 0.76 VT = 0.74

Window 2 Double Glazing Clear Glass Aluminum Frame

U = 0.79 SHGC = 0.68 VT = 0.67

Window 3 Double Glazing Low-E Coating
(low solar gain)* Aluminum Frame
with Thermal Break

U = 0.48 SHGC = 0.34 VT = 0.53

Window 4 Double Glazing Clear Glass Wood, Vinyl, Clad or
Hybrid/Composite Frame

U = 0.49 SHGC = 0.56 VT = 0.58

Window 5 Double Glazing Low-E Coating
(high solar gain) Wood, Vinyl, Clad or
Hybrid/Composite Frame

U = 0.36 SHGC = 0.52 VT = 0.53

Window 6 Double Glazing Low-E Coating
(low solar gain)* Wood, Vinyl, Clad or
Hybrid/Composite Frame

U = 0.32 SHGC = 0.30 VT = 0.50

*Spectrally Selective

Source: Adapted with permission from the Efficient Windows Collaborative.

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Windows and Doors

.uture Window Options
Electronic windows
A new genre of windows is composed of special materials that can darken the glazing by running electricity through the unit. Some manufacturers already have prototypes of these high technology windows in operation. At night and on sunny days, an electric switch can be turned on to render the windows virtually opaque.
Solid windows
Another new window technology uses gel-type material up to one inch thick between layers of glazing. The window offers increased insulating value, but at present is not completely transparent and is not economical in Georgia.

PROPER WINDOW INSTALLATION
Step 1: Make sure window fits in rough opening and that the sill is level.
Step 2: Install window level and plumb according to the manufacturer's instructions.
Step 3: Use non-expanding foam sealant to seal between the jamb and the rough opening, or stuff the gap with backer rod or insulation and cover the insulation with caulk (remember--most insulation doesn't stop air leaks--it just serves as a filter).
Step 4: If using an interior polyethylene air/vapor barrier or exterior air barrier, seal the barrier to the window jamb with long-life caulk or other appropriate, durable sealant.
Step 5: After interior and exterior trim is installed, seal the gap between the trim and the interior or exterior finish with long-life caulk.

Table 6-3 Economics of Energy Conserving Windows and Doors*

Type of Treatment
Windows 1. All windows double-glazed (R-1.7) (compared to single-glazed windows)
2. All windows double-glazed with low-emissivity coating (R-2.6) (compared to Case 1)
3. All windows double-glazed with low-emissivity coating and inert gas fill (R-3.1) (compared to Case 1)
4. All windows with double glass, double inner film with low-emissivity coating, inert gas fill (R-4.8) (compared to Case 1)
Doors (compared to solid wood doors) 1. Foam insulated doors (R-7)

Incremental Energy Savings
($/yr) 133 52
67
96
20

Incremental Installed Costs ($)** 400 450
550
1,750
60

Rate of Return 39.0% 15.0% 16.4% 6.0%
39.0%

2. Storm doors over solid wood doors (R-3.2)

9

150

6.4%

Incremental Mortgage Costs ($/yr) 37 41
51
101
6 14

* Savings and costs are for a two-story home with 254 square feet of windows and 2 exterior doors located in Atlanta, GA.
**Window and door costs vary widely. Markedly different values may be found from some distributors.

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Doors
Exterior wood doors have low insulating values, typically R-2.2. Storm doors increase the R-value only to about R-3.0 and are not good energy investments. The best energy-conserving alternative is a metal or fiberglass insulated door. Metal doors have a foam insulation core which can increase the insulating value to above R-7. They usually cost no more than conventional exterior doors and come in decorative styles, complete with raised panels and insulated window panes.
Insulated metal or fiberglass doors usually have excellent weatherstripping and long lifetimes. They will not warp, and offer increased security; however, they are difficult to trim, so careful installation is required. Table 6-3 examines the costs and savings of energy conserving doors. As with windows, it is important to seal the rough openings. Thresholds should seal tightly against the bottom of the door and must be caulked underneath. After the door is installed, check it carefully when closed to see if there are any air leaks.
Accessible Design
Almost one out of ten people will suffer from physical disabilities during their lifetime. Designing homes to ensure accessibility for the physically impaired adds little to the cost of a home. One important feature is to ensure that both exterior and interior door openings and hallways are 3'-0" wide to allow passage of a wheelchair or walker. Ensuring that baths and kitchens have adequate room for wheelchairs is another feature that adds little to construction costs but is expensive to retrofit.
Windows and Ventilation
Natural Ventilation
A primary purpose of windows is to provide for ventilation. With Georgia's mild climate, natural ventilation can maintain comfort for much of the spring and fall. The size and placement of the window openings affect ventilation. Casement windows open fully for ventilation, while double-hung and slider windows open only 50 percent of their total area. In addition, casement windows can be used to channel breezes into the home.

.igure 6-7 Insulated Metal Door
Wood framing
Metal surface of door
Foam insulation
The optimum placement of windows for ventilation would be on each side of the house to take advantage of breezes from any direction. However, the ventilation benefits of east and west windows are overshadowed by the problems they pose by allowing summer sunlight into the home. In general, it is best to avoid east and west windows. Place the major glass areas on the south and a moderate number of windows on the north for cross ventilation.
Each room should have a window to allow air to enter (ideally located on the south or north wall) and a separate opening to enable air to exit. The outlet may be a doorway leading into another area of the home. The inlet and outlet should be located so that they create breezes in the areas most frequently occupied.
In addition to providing for cross ventilation, windows can be used to create ventilation between low and high areas. For example, in a two-story house, as air inside warms it rises and exits through upper level windows. As the air rises, it draws outside air through the lower windows into the house. This process is known as the stack effect. However, the force of the rising air is weak, so it is not practical to provide special design features in a house to encourage this type of ventilation.
In fact, natural ventilation of any type is unpredictable. While having some operable windows is desirable, it is not usually worthwhile to increase construction costs solely to increase the window area for ventilation. Mechanical ventilation provided by fans is economical and much more reliable.

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Windows and Doors

Mechanical Ventilation

Windows and Shading

Mechanical ventilation--using fans or blowers-- provides an inexpensive means of creating a cooling air flow. Internal air movement created by portable fans or ceiling fans can provide comfort inexpensively. Use fans even when the air conditioning is operating. For each degree that the thermostat is raised, air conditioning costs drop 3 to 8 percent. By setting the thermostat between 80 and 85F and using fans, homeowners can save 20 to 50 percent on cooling bills.
Whole house fans, also called attic fans, blow hot room air from inside up into the attic and pull supply air into the home from outside. Be sure to construct an insulated cover for the whole house fan and place it in the attic.
The primary disadvantage of whole house fans is that they bring in outside air containing dust and, at times, pollen and other allergens. They also pull in moisture. However, for most people, whole house fans can save considerably on cooling bills. In fact, some homes without air conditioning rely solely on whole house fans to maintain comfort.
Whole house fans can be coupled with ceiling fans to reduce cooling costs 50 to 70 percent as follows:
s When it is hotter than 85F outside, set the air conditioner thermostat at 85F and run ceiling and portable fans. Do not use whole house fan when air conditioning.
s When it is cooler than 85F outside and not excessively humid, turn the air conditioner off, open the windows, and run the whole house fan.
s On days when temperatures do not rise above 85F until mid- or late afternoon, try ventilating during the cooler morning hours. As temperatures increase, close windows and pull shades to keep the heat outside. Use interior fans to create a breeze. As temperatures cool in the evening, open the house and ventilate.
See Chapter 7 for more information on ventilation strategies.

Shading Coefficients
An important characteristic of windows is the shading coefficient (SC), which measures how much sunlight is transmitted through a window compared to that transmitted through clear, single-glazed glass. The more layers of glass, coatings, or tints that a window has, the more sunlight it impedes and hence, the lower the shading coefficient. Typical values are shown in Table 6-4.
In sections of Georgia with hotter summers and warmer winters, tinted glass may be recommended for windows that face east, west and south. These windows have lower shading coefficients and block sunlight in summer so as to reduce cooling bills.

Table 6-4 Window Treatment Shading Coefficients

Treatment

Window Type

Shading Coefficient*

Single-glazed window

1/8-inch glass -inch glass tinted (-inch)

1.00 .94 .78

Double-glazed

1/8-inch glass

.88

window

-inch glass

.81

tinted (-inch)

.67

Venetian blinds

-inch single glass

.60

-inch double glass

.54

Roller blinds (white)

-inch single glass

.25

-inch double glass

.25

Light, airy drapes

-inch single glass

.70

-inch double glass

.58

Heavy drapes

-inch single glass

.45

-inch double glass

.42

Exterior shade

-inch single glass

.38

screen/louvered -inch double glass

.42

sun screen

*Fraction of sunlight that passes through glass and window treatment. Assumes sunlight strikes perpendicular to glass. SHGC ~ 0.89 x SC

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Windows and Doors

Window Shading Options
Most windows in Georgia require shading devices other than window tinting. Options include:
s Overhangs s Blinds s Shutters s Landscaping and trees
The effectiveness of different window shading options depends on the composition of the incoming sunlight. Sunlight reaches the home in three forms: direct, diffuse, and ground reflected. On a clear day, most sunlight is direct, traveling as a beam without obstruction from the sun to a home's windows. In winter, most of the direct sunlight striking a window is transmitted; however, in summer, the sun strikes south windows at a much steeper angle, and much of the direct sunlight is reflected.
The majority of the sunlight entering south-facing windows in the summer is either diffuse--bounced between the particles in the sky until it arrives as a bright haze--or is reflected off the ground.
In developing a strategy for effectively shading windows, both direct and indirect sources of sunlight must be considered. Overhangs, long thought to be totally effective for shading south-facing windows, are best at blocking direct sunlight and are therefore only a partial solution.
Overhangs
Overhangs shade direct sunlight on windows facing within about 30 degrees of south. Overhangs on east and west windows are ineffective unless they are as long as the window is high.
Overhangs above south-facing windows should provide complete shade for the glazing in midsummer-- around July 21--yet still allow access to winter sunlight. For a standard 8-foot wall with windows, the overhang should be 2 to 2 feet in length. Make certain that there is a gap between the bottom of the overhang and the top of the glazing to prevent shading the upper portion of the glass in winter. Figure 6-8 illustrates a method for sizing overhangs above south-facing windows.
Retractable awnings allow full winter sunlight, yet provide effective summer shading. They should have open sides or vents to prevent accumulation of hot air underneath. Awnings may be more expensive than other shading options, but they serve as an attractive design feature.

.igure 6-8 Guidelines for Overhangs

2

3

4

5

35 degrees

1
75 degrees

8 feet

Size south overhangs using the diagram above and these rules:

1. Draw to scale the wall to be shaded by the overhang.
2. Draw the summer sun angle upward from the bottom of the glazing.
3. Draw the overhang until it intersects the summer sun angle line.
4. Draw the line at the winter sun angle from the bottom edge of the overhang to the wall.
5. Use a solid wall above the line where the winter sun hits. The portion of the wall below that line should be glazed.

Summer and Winter Sun Angles (Degrees from horizon at noon)

Dalton Atlanta Macon Valdosta

July 21 73 74 75 76

January 21 33 34 35 36

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81

Windows and Doors

External shades and shutters
Exterior window shading treatments are effective cooling measures because they block both direct and indirect sunlight before it enters windows. Solar shade screens are an excellent exterior shading product with a thick weave that blocks up to 70 percent of all incoming sunlight before it enters the windows. The screens absorb sunlight so they should be used on the outside of the windows. From the outside, they look slightly darker than regular screening, and provide greater privacy. From the inside many people do not detect a difference. Most products also serve as insect screening and come in several colors. They should be removed in winter to allow full sunlight through the windows. A more expensive alternative to the fiberglass product is a thin, louvered metal screen that blocks sunlight, but still allows a view from inside to outside.
Hinged decorative exterior shutters which close over the windows are also excellent shading options. However, they obscure the view, block daylight, can be expensive, are subject to wear and tear, and can be difficult to operate on a daily basis.
Interior shades and shutters
Shutters and shades located inside the house include curtains, roll-down shades, and Venetian blinds. More sophisticated devices, such as shutters that slide over the windows on a track and interior movable insulation, are also available.
Interior shutters and shades are generally the least effective shading measures because they try to block sunlight that has already entered the room. However, if east-, south-, or west-facing windows do not have exterior shading, interior measures are needed. The most effective interior treatments are solid shades with a reflective surface facing outside. In fact, simple white roller blinds keep the house cooler than more expensive louvered blinds, which do not provide a solid surface and allow trapped heat to migrate between the blinds into the house.
Reflective films and tints
Reflective film, which adheres to glass and is found often in commercial buildings, can block up to 85% of incoming sunlight. The film blocks sunlight all year, so it is inappropriate on south windows in passive solar homes. However, it may be practical for unshaded east and west windows. It is not recom-

Table 6-5 Shading Coefficients for
Window Coverings

Type of Covering

Shading

Coefficient*

None

0.88

Medium-colored venetian blinds

0.57

Opaque dark shades

0.60

Opaque white shades

0.25

Translucent light shades

0.37

Open weave dark draperies

0.62

Close weave light draperies

0.45

*Lower numbers shade better. The table assumes windows are double-glazed. Source: ASHRAE Handbook of Fundamentals, 1985.
mended for windows that experience partial shading because as the film absorbs sunlight it may heat the glass unevenly. The uneven heating of windows may break the glass or ruin the seal between doubleglazed units.
The installed cost of reflective films ranges from $1 to $4 per square foot. Price should not be the sole criterion when selecting an installer--quality is a vital consideration affecting the appearance of the house and the beauty of the view to the outside.
Most window manufacturers offer tinted windows, which block sunlight all year. They can have shading coefficients under .30. The window tints can add color, such as green, amber, rose, or blue to the window. In some cases, the window can have a reflective finish to block additional sunlight. These tints are often inexpensive, costing only $3 to $10 extra per window for many units. However, don't forget that the tint is permanent, so incoming sunlight will be blocked in both summer and winter.
Landscaping and trees

Georgia's abundant trees are wonderful for natural shading, but they must be located appropriately so as to provide shade in summer and not block the winter sun coming from the south. Even deciduous trees that lose their leaves during cold weather block some winter sunlight--a few bare trees can block over 50 percent of the available solar energy. Some guidelines for energy efficient landscaping are shown in Figure 6-9.

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Builders Guide to Energy Efficient Homes in Georgia

.igure 6-9 Landscaping Guidelines

Windows and Doors

6 4

5

1

2

3

S

1. Major glass areas are oriented within 20 degrees of south and have overhangs for summer shading. 2. Ground cover reduces reflected sunlight. 3. Deciduous trees shade east, west, southeast, and southwest sides in summer. 4. Trellis with deciduous vine shades east wall. 5. Garage on west blocks summer sun and winter winds. 6. Windbreak of evergreen trees and shrubs to the north buffers winter winds.

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83

Windows and Doors
Notes:

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Builders Guide to Energy Efficient Homes in Georgia

Heating, Ventilation, Air Conditioning (HVAC)

7. Heating, Ventilation, Air Conditioning (HVAC)

One of the most important decisions regarding a
new home is the type of heating and cooling system to install. Equally critical is the heating and cooling contractor selected, as the operating efficiency of a system depends as much on proper installation as on the performance rating. Keys to obtaining the design efficiency of a system in the field include:
s Sizing the system for the specific heating and cooling load of the home being built
s Selection and proper installation of controls
s Correct design of the ductwork or piping
s Insulating and sealing all ductwork
Improper installation of components, in particular of ductwork, has negative impacts on comfort and energy bills, and can dramatically degrade the quality

of air in a home. Poorly designed and installed ducts can create dangerous conditions that may reduce comfort, degrade indoor air quality, or even threaten the lives of the homeowners.
Types of HVAC Systems
There are two primary types of central heating systems--forced air systems and radiant heating systems. Most new homes have forced-air heating and cooling systems--either using a central furnace and air conditioner or a heat pump. As shown in Figure 7-1, in forced air systems, a series of ducts distributes the conditioned heated or cooled air throughout the home. The conditioned air is forced through the ducts by a blower, located in a unit called an air handler.

Return plenum Filter Blower Heating source Refrigerant lines

.igure 7-1 Components of .orced Air Systems

Builders Guide to Energy Efficient Homes in Georgia

Supply plenum Branch duct Trunk duct Indoor coil
Condensate line
85

Heating, Ventilation, Air Conditioning (HVAC)

RADIANT HEATING SYSTEMS

Radiant systems typically combine a central boiler or water heater with piping to transport steam or hot water into the living area. Heating is delivered to the rooms in the home via radiators or radiant floor systems, such as radiant slabs or underfloor piping.
Advantages of radiant systems include:
s Quieter operation than heating systems that use forced air blowers.
s The higher radiant temperatures of the radiators or floors allow people to feel warmer at lower air temperatures--some homeowners with radiant heating report being comfortable at room air temperatures of 60oF.
s Better zoning of heat delivered to each room.
s Many homeowners with radiant systems find the heating more comfortable.

However, there are disadvantages with radiant systems:
s Radiant systems typically cost 40 to 60% more to install than comparable forced air heating systems.
s They do not include provisions for cooling--the cost of a radiant heating system combined with central cooling would be difficult to justify economically; some designers of two-story homes have specified radiant heating on the bottom floor and forced air heating and cooling on the second floor.
s Because air is not cycled between the system and the house, there is no filtering of air.
s Parts and a choice of dealers may be more difficult to find.

.igure 7-2 Radiant Heating Options

Thermostat to control valve
Radiator
Coernhhtoertaatwlbearot;yileer;yr ;y;y;y;y;y;y;y;y;y;y;y;y;y;y;y;;;;;;;yyyyyyy;;yy;;;;;;;yyyyyyy

Radiant under- floor
piping
Co;yern;yhhtoer;ytaatwl;ybearo;ytilee;yrr ;y;y;y;y;y;y;y;y;;;;;;;yyyyyyy;y;;;;;;;;yyyyyyyy;y;;yy
Radiant slab

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Builders Guide to Energy Efficient Homes in Georgia

Heating, Ventilation, Air Conditioning (HVAC)

Most homes in Georgia have a choice of two approaches for central, forced air systems: fuel-fired furnaces with electric air conditioning units or electric heat pumps. The best system for each home depends on the cost and efficiency of the equipment, annual energy use, and the local price and availability of energy sources. In most homes, either type of system, if designed and installed properly, will deliver comfort economically.
When considering a HVAC system for a residence, remember that energy efficient and passive solar homes have less demand for heating and cooling, so substantial savings may be obtained by installing smaller units that are properly sized to meet the load. Because energy bills in more efficient homes are lower, higher efficiency systems will not provide as much annual savings on energy bills and may not be as cost effective as in less efficient homes.
Sizing

Table 7-1 compares the size of heating and cooling systems for two homes with identical floor areas. The more efficient home reduces the heating load 35% and the cooling load 26%. Thus, the additional cost of the energy features in the more efficient home is offset by the $600 to $1,000 savings from reducing the size of the HVAC equipment.
Oversimplified rules of thumb would have provided an oversized heating and cooling system for the more efficient home. The oversized unit would have cost more to install. In addition, the operating costs would be higher, it would suffer greater wear, and it may not provide adequate dehumidification.
Proper sizing includes designing the cooling system to provide adequate dehumidification. In Georgia's humid climate it is critical to calculate the latent load-- the amount of dehumidification needed for the home. If the latent load is ignored, the home may become uncomfortable due to excess humidity.

It is important to size heating and air conditioning systems properly. Not only does oversized equipment cost more, but it can waste energy and may decrease comfort. For example, an oversized air conditioner cools a house but may not provide adequate dehumidification, thus creating cool, but clammy air.
Do not rely on rule-of-thumb methods to size HVAC equipment. Many contractors select air conditioning systems based on a rule such as 600 square feet of cooled area per ton of air conditioning (a ton provides 12,000 Btu per hour of cooling). Instead, use a sizing procedure such as:
s Calculations in Manual J published by the Air Conditioning Contractors Association
s Similar procedures developed by the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE)
s Software procedures developed by electric or gas utilities, the U.S. Department of Energy, or HVAC equipment manufacturers
The heating and cooling load calculations should be based on the exact area and type of construction for each component of the building envelope, as well as the heat given off by the lights, people, and equipment inside the house. If a zoned heating and cooling system is used, the loads in each zone should be calculated.

Table 7-1 Equipment Sizing and Cost Comparison

Type of House

More

Less

Efficient Efficient

Insulation R-Values

and Areas:

R-30 Attic

2,000 sq ft 1,000 sq ft

R-25 Cathedral Ceiling 0 sq ft 1,000 sq ft

Wall Area/ R-value

1,750 sq ft/ 1,600 sq ft/

R-21

R-16

Window Area/ R-value 250/ R-3 400/ R-2

Floors

2,000/ R-21 2,000/ R-13

Air Leakage (ach)*

0.35

0.60

Duct Leakage (CFM25)** 50

250

HVAC System Sizing:

Heating(Btu/hour)

22,000

Cooling(Btu/hour)

20,000

Estimated tons of cooling*** 2

Square feet/ton

1,000

34,000 27,000
2.5 800

Typical Equipment Cost:

Lower Efficiency

$3,600

Higher Efficiency

$4,000

$4,200 $4,700

* ach means the number of natural air changes per hour the home has due to air leakage.
** CFM25 is the duct leakage rate at a pressure of 25 Pascals-- a standard number used during a duct leakage test.
*** There are 12,000 Btu/hour in a ton of cooling.

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Heating, Ventilation, Air Conditioning (HVAC)

MANUAL J EXAMPLE*

Manual J, Load Calculation for Residential Winter and Summer Air Conditioning, is published by the Air Conditioning Contractors of America (ACCA.) The procedures in the manual calculate the building heating and cooling loads as follows:
1. Determine all dimensions of the exterior building envelope for each type of surface (wall, floor, window, door, ceiling, etc.)
2. Note R-values of all components.
3. Find the Construction Number of each component based on tables in the book.
4. Look up climatic data in the manual for the locality in which the home is being constructed.
5. Based on the Construction Number and the climatic data, find the Heat Transfer Multiplier (HTM) for the different components during the heating (Htg.) and cooling (Clg.) seasons.
6. Fill in the tables for the heating and cooling load.
7. Calculate the infiltration loads, internal gains, and latent loads in separate charts.
8. Find the grand total loads.
9. Use Manual S, Residential Equipment Selection, also published by ACCA, to help select the equipment for the home.

1 Name of Room 2 Running Ft. Exposed Wall 3 Room Dimensions Ft. 4 Ceiling Ht. Ft.

Entire House 94.5
32 62.5 8

TYPE OF EXPOSURE

Const. HTM Area/

Btuh

No. Htg. Clg. Length Htg. Clg.

5 Gross

a 12F

Exposed

b

Walls &

c

Partitions

d

6 Windows

a 3b 30.5

& Glass

b

Doors Htg. c

d

7 Windows North

& Glass E&W

Doors Clg. South

1,512
300 9,150
16 75 46 150 25 75

1,200 6,900 1,875

8 Other Doors

10D 23 10.9 42

9 Net

a 12F 3.5 1.7 1,170

Exposed

b

Walls &

c

Partitions

d

10 Ceilings

a 16G 1.6 1.2 2,000

b

11 Floors

a 19D 1.3

0 2,000

b

12 Infiltration HTM

13 Sub Total Btuh Loss = 6+8+9+10+11+12

14 Duct Btuh Loss

0.1

15 Total Btuh Loss = 13 + 14

16 People @ 300 & Appliances= 1200

17 Sensible Btuh Gain = 7+8+9+10+11+12+16

18 Duct Btuh Gain

0.05

19 Total Sensible Gain

966 4,095
3,200
2,600
11,757 31,768
3,177 34,945

458 1,989
2,400
0
5,878 20,700
0
2,400 23,100
1,155 24,255

Latent Gain Calculations Latent Infiltration Latent Ventilation Latent Internal Gains
Total Latent Gain

2,471 0
1,920 4,391

* A Manual J calculation takes approximately 30 to 60 minutes for an average home. The measurements for the calculations are available from the construction drawings. Manual S calculations require an additional 15 to 30 minutes.

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Heating, Ventilation, Air Conditioning (HVAC)

The Sensible Heating Fraction (SHF) designates the portion of the cooling load for reducing indoor temperatures (sensible cooling). For example, in a HVAC unit with a .75 SHF, 75% of the energy expended by the unit goes to cool down the temperature of indoor air. The remaining 25% goes for latent heat removal--taking moisture out of the air in the home. To accurately estimate the cooling load, the designer of a HVAC system must also calculate the desired SHF and thus, the latent load.
Many homes in Georgia have design SHF's of approximately 0.7--70% of the cooling will be sensible and 30% latent. Systems that deliver less than 30% latent cooling may fail to provide adequate dehumidification in summer.

Temperature Controls
The most basic type of control system is a heating and cooling thermostat. Programmable thermostats, also called setback thermostats, can be big energy savers for homes by automatically adjusting the temperature setting when people are sleeping or are not at home. Be certain that the programmable thermostat selected is designed for the particular heating and cooling equipment it will be controlling. This is especially important for heat pumps, as an improper programmable thermostat can actually increase energy bills.
A thermostat should be located centrally within the house or zone. It should not receive direct sunlight or

COOLING EQUIPMENT SELECTION
Table 7-2 and 7-3 show equipment charts for two sample air conditioning units. Each system provides a wide range of outputs, depending on the blower speed and the temperature conditions. The SHF in the chart is the Sensible Heating Fraction--the fraction of the total output that cools down the air temperature. The remainder of the output dehumidifies the air--provides latent cooling. Note that both systems provide about 36,000 Btu/ hour of cooling.
System A: with 80o return air, SEER = 12.15
At low fan speed, provides 35,800 Btu/hour, 0.71 SHF, and thus 29% latent cooling (dehumidification).
At high fan speed, provides 38,800 Btu/hour, but a 0.81 SHF, and only 19% latent cooling--not enough dehumidification in many Georgia homes.
System B: with 80o return air, SEER = 11.55
At low fan speed, provides 32,000 Btu/ hour, 0.67 SHF and 33% dehumidification.
At high fan speed, provides 35,600 Btu/hour, 0.76 SHF and 24% dehumidification.
Thus, System A, while nominally more efficient than B, provides less dehumidification and potentially less comfort.

Table 7-2 Sample Cooling System A Data

Total Ain Volume (cfm) 950 1,200 1,450

Total Cooling Capacity (Btuh) 35,800 37,500 38,800

Sensible Heating

Fraction (SHF)

Dry Bulb (deg F)

75oF

80oF

85oF

0.58 0.71 0.84

0.61 0.76 0.91

0.64 0.81 0.96

Table 7-3 Sample Cooling System B Data

Total Ain Volume (cfm)

Total Cooling Capacity (Btuh)

Sensible Heating

Fraction (SHF)

Dry Bulb (deg F)

75oF

80oF

85oF

950 1,200 1,450

32,000 34,100 35,600

0.56 0.58 0.61

0.67 0.71 0.76

0.78 0.84 0.90

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Heating, Ventilation, Air Conditioning (HVAC)

Table 7-4 Typical Savings from Programmable Thermostats

Winter Heating Setting
72F Day/72F Night 72F Day/65F Night 68F Day/68F Night 68F Day/60F Night 68F Day/55F Night

Energy Savings ($/yr)
0 28 48 74 77

be near a heat-producing appliance. A good location is often 4 to 5 feet above the floor in an interior hallway near a return grille.
The interior wall on which it is installed, like all walls, should be well sealed at the top and bottom to prevent circulation of cool air in winter or hot air in summer. Some homeowners have experienced discomfort and increased energy bills for years because air from the attic leaked into the wall cavity behind the thermostat and caused the cooling or heating system to run much longer than needed.

still tries to deliver the same air flow as before, but now through only a few ducts. Back pressure created against the blades of the blower may cause damage to the motor. There are three primary design options:
1. Create two zones and oversize the ductwork so that when the damper to one zone is closed, the blower will not suffer damage.
2. Install a manufactured system that uses a dampered bypass duct connecting the supply plenum to the return ductwork. These controls always allow the same approximate volume of air to circulate.
3. Use a variable speed HVAC system. Because variable speed systems are usually more efficient than single-speed systems, they will further increase savings.
.igure 7-3 Automatic Zoned System

Zoned HVAC Systems

Larger homes often use two or more separate heating and air conditioning units for different floors or areas. Multiple systems can maintain greater comfort throughout the house while saving energy by allowing different zones of the house to be at different temperatures. The greatest savings come when a unit serving an unoccupied zone can be turned off.
Rather than install two separate systems, HVAC contractors can provide automatic zoning systems that operate with one system. The ductwork in these systems typically has a series of thermostatically controlled dampers that regulate the flow of air to each zone. Although somewhat new in residential construction, thermostats, dampers, and controls for zoning large central systems have been used for years in commercial buildings.
If your heating and air conditioning subcontractor feels that installing two or three separate HVAC units is necessary, have him or her also estimate the cost of a single system with damper control over the ductwork. Such a system must be carefully designed to ensure that the blower is not damaged if dampers are closed to several supply ducts. In this situation, the blower

Air flow to Both Zones Bypass damper opens automatically
Air Flow to One Zone

Damper closed by thermostat
in zone

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Heating, Ventilation, Air Conditioning (HVAC)

Air Conditioning Equipment
Air conditioners and heat pumps work similarly to provide cooling and dehumidification. In the summer, they extract heat from inside the home and transfer it outside. In winter, a heat pump reverses this process and extracts heat from outside and transfers it inside.
Both systems typically use a vapor compression cycle, which is described in a sidebar. This cycle circulates a refrigerant, a material that increases in temperature significantly when compressed and cools rapidly when expanded. The exterior portion of a typical air conditioner is called the condensing unit and houses the compressor, the noisy part that uses most of the energy, and the condensing coil.
An air-cooled condensing unit should be kept free from plants and debris that might block the flow of air through the coil or damage the thin fins of the coil. Ideally the condensing unit should be located in the shade. However, do not block air flow to this unit with dense vegetation, fencing or overhead decking.
The inside mechanical equipment, called the airhandling unit, houses the evaporator coil, the indoor blower, and the expansion, or throttling valve. The controls and ductwork for circulating cooled air to the house complete the system.
The SEER Rating
The cooling efficiency of a heat pump or an air conditioner is rated by the Seasonal Energy Efficiency Ratio (SEER), a ratio of the average amount of cooling provided during the cooling season to the amount of electricity used. Current national legislation mandates a minimum SEER 10.0 for most residential air conditioners. Efficiencies of some units can exceed SEER 15.0. Packaged units, which combine the outdoor and indoor components into one package located outside, have a minimum SEER of 9.5.
Builders should be aware that the SEER rating is a national average based on equipment performance in Virginia. Some equipment may not produce the listed SEER in actual operation in Georgia's homes. One of

the main problems has been the inability of some higher efficiency equipment to dehumidify homes adequately.
If units are not providing sufficient dehumidification, the typical homeowner response is to lower the thermostat setting. Since every degree the thermostat is lowered increases cooling bills 3 to 7%, systems that have nominally high efficiencies, but inadequate dehumidification may suffer from higher than expected cooling bills.
In fact, poorly functioning "high" efficiency systems may actually cost more to operate than a well designed, moderate efficiency unit. Make certain that the contractor has used Manual J techniques so that the air conditioning system meets both sensible and latent (humidity) loads at the manufacturer's claimed efficiency.
Variable Speed Units
The minimum standard for air conditioners of SEER 10.0 provides for a reasonably efficient unit. However, higher efficiency air conditioners may be quite economical. Table 7-4 examines the economics of different options for a sample home.
In order to increase the overall operating efficiency of an air conditioner or heat pump, multispeed and variable speed compressors have been developed. These compressor units can operate at low or medium speeds when the outdoor temperatures are not extreme. They can achieve a SEER of 15 to 16.
The cost of variable speed units is generally about 30% higher than standard units. Advantages they offer over standard, single-speed blowers:
s They usually save energy.
s They are quieter, and because they operate fairly continuously, there is far less start-up noise (often the most noticeable sound in a standard unit.)
s They dehumidify better. Some units offer a special dehumidification cycle, which is triggered by a humidistat that senses when the humidity levels in the home are too high.

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Heating, Ventilation, Air Conditioning (HVAC)

AIR CONDITIONERS AND HEAT PUMPS
Air Conditioners use the vapor compression cycle, a 4-step process:

1. The compressor (in the

2

4

outside unit) pressurizes a

gaseous refrigerant.The

refrigerant heats up during

this process.

2. Fans in the outdoor unit

blow air across the

heated, pressurized gas in

the condensing coil; the

refrigerant gas cools and condenses into a liquid.

1

3. The pressurized liquid is

3

piped inside to the air-handling unit. It enters a throttling or expansion valve, where it expands and cools.

4. The cold liquid circulates through evaporator coils. Inside air is blown across the coils and cooled while the refrigerant warms and evaporates. The cooled air is blown through the ductwork. The refrigerant, now a gas, returns to the outdoor unit where the process starts over.

Heat pumps use a reversed version of the same cycle for heating. A reversing valve allows the heat pump to work automatically in either heating or cooling mode. The steps for heating are:

1. The compressor (in the

outside unit) pressurizes

4

2

5

the refrigerant, which is piped inside.
2. The hot gas enters the

inside condensing coil.

Room air passes over the

coil and is heated. The

refrigerant cools and

condenses.

1

3

3. The refrigerant, now a pressurized liquid, flows outside to a throttling valve where it expands to become a cool, low pressure liquid.

4. The outdoor evaporator coil, which serves as the condenser in the cooling process, uses outside air to boil the cold, liquid refrigerant into a gas. This step completes the cycle. 5. If the outdoor air is so cold that the heat pump cannot adequately heat the home, electric resistance strip heaters usually provide supplemental heating. 6. Periodically in winter, the heat pump must switch to a "defrost cycle," which melts any ice that has formed on the outdoor coil.
Packaged systems and room units use smaller versions of these components in a single box.

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Type of Treatment

Table 7-5 Air Conditioner Economics*

Incremental Energy Savings
($/yr)

Incremental Installed Costs ($)

Annual Rate of Return

Incremental Mortgage Costs ($/yr)

SEER 11 (3 tons)--Compared to SEER 10

45

SEER 13 (3 tons)--Compared to SEER 11

135

SEER 11 (5 tons)--Compared to SEER 10

67

SEER 13 (5 tons)--Compared to SEER 11

202

250

19.8%

4

650

24.5%

57

425

18.6%

37

725

31.0%

64

*For Atlanta, GA

Proper Installation
Too often, high efficiency cooling and heating equipment is improperly installed, which can cause it to operate at substantially reduced efficiencies. A SEER 12 air conditioning system that is installed poorly with leaky ductwork may only deliver a SEER 7. Typical installation problems are:
s Improper charging of the system--the refrigerant of the cooling system is the work horse-- it flows back and forth between the inside coil and the outside coil, changing states, and undergoing compression and expansion. The HVAC contractor should use the manufacturer's installation procedures to charge the system properly. The correct charge cannot be ensured by pressure gauge measurements alone. In new construction, the refrigerant should be weighed in.
s Reduced air flow --if the system has poorly designed ductwork, constrictions in the air

distribution system, clogged or more restrictive filters, or other impediments, the blower may not be able to transport adequate air over the indoor coils of the cooling system. Reduced air flow of 20% can drop the operating efficiency of the unit by about 1.7 SEER points; thus a unit with a SEER of 10.0 would only operate at SEER 8.3.
s Inadequate air flow to the outdoor unit-- if the outdoor unit is located under a deck or within an enclosure, adequate air circulation between the unit and outdoor air may not occur. In such cases, the temperature of the air around the unit rises, thereby making it more difficult for the unit to cool the refrigerant that it is circulating. The efficiency of a unit surrounded by outdoor air that is 10 degrees warmer than the ambient outside temperature can be reduced by over 10%.

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Heating Systems
Two types of heating systems are most common in new homes--furnaces, which burn natural gas, propane, or fuel oil, and electric heat pumps. Furnaces are generally installed with central air conditioners. Heat pumps provide both heating and cooling. Some heating systems are integrated with water heating systems.

.igure 74 Types of Heat Pumps
Air-Source Heat Pump

Heat Pump Equipment

Air-source heat pumps
The most common type of heat pump is the airsource heat pump, which extracts heat from warm inside air in the summer, just like an air conditioner. In winter, it reverses the cycle and obtains heat from cool outside air. Most heat pumps operate at least twice as efficiently as conventional electric resistance heating systems. They have typical lifetimes of 15 years, compared to 20 years for most furnaces.
At outside temperatures of 25 to 35F, a temperature known as the balance point, heat pumps can no longer meet the entire heating load of the home, so many use electric resistance coils called strip heaters to provide supplemental backup heat. Strip heaters, located in the air handling unit, are much more expensive to operate than the heat pump itself. They should not be oversized, as they can drive up the peak load requirements of the local electric utility. A staged, heat pump thermostat can be used in concert with multi-stage strip heaters to minimize strip heat operation. To overcome this problem, some houses use a dual-fuel or piggyback system that heats the home with natural gas or propane when temperatures drop below the balance point.
Air-source heat pumps should have outdoor thermostats, which prevent operation of the strip heaters at temperatures above 35oF or 40 oF. The energy code requires controls to prevent strip heater operation during weather when the heat pump alone can provide adequate heating.
Geothermal heat pumps

Geothermal Heat Pumps Shallow trench loop
Deep well loop

Unlike an air-source heat pump which has an outside heat exchanger, a geothermal heat pump relies on fluid-filled pipes buried beneath the earth as a source of heating in winter and cooling in summer. In each season, the temperature of the earth is closer to the desired temperature of the home, so less energy

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is needed to maintain comfort. Eliminating the outside equipment means higher efficiency, less maintenance, greater equipment life, no noise, and no inconvenience of having to mow around that outdoor unit.
Geothermal heat pumps have SEER ratings above 15 and can save up to 40% on the heating and cooling costs for a standard air-source heat pump. Some products have greater dehumidification ability than air-source heat pumps. Many units can also provide hot water at much greater efficiency than standard electric water heaters. Because of the warmer temperatures of the earth, geothermal heat pumps deliver heated air in winter into the home at a temperature between 95 to 110oF.
There are several types of closed loop designs for piping:
s In deep well systems, a piping loop extends several hundred feet under ground.
s Shallow loops are placed in long trenches, typically about 6-feet deep and several hundred feet long. Coiling the piping into a "slinky" reduces the length requirements.
s For homes located on private lakes, loops can be installed at the bottom which usually decreases the installation costs and may improve performance.
Proper installation of the geothermal loops is essential for high performance and the longevity of the system, so choose only qualified professionals who have several years' experience installing geothermal heat pumps similar to that designed for your home.

Geothermal heat pumps provide longer service than air-source units. The inside equipment should last as long as any other traditional heating or cooling system. The buried piping usually has a 25-year warranty. Most experts believe the piping will last longer because it is made of a durable plastic with heat-sealed connections, and the circulating fluid has an anticorrosive additive.
Geothermal heat pumps cost $1,000 to $1,500 more per ton to install than conventional air-source heat pumps. The actual cost varies according to the difficulty of installing the ground loops as well as the size and features of the equipment. Because of their high installation cost, geothermal heat pumps may not be economical for homes with low heating and cooling needs. However, their lower operating costs, reduced maintenance requirements, and greater comfort may make them attractive to many homeowners.
Measures of efficiency for heat pumps
The heating efficiency of a heat pump is measured by its Heating Season Performance Factor (HSPF), which is the ratio of heat provided in Btu per hour to watts of electricity used. This factor considers the losses when the equipment starts up and stops, as well as the energy lost during the defrost cycle.
Typical values for the HSPF are 6.8 for standard efficiency, 7.2 for medium efficiency, and 8.0 for high efficiency. Variable speed heat pumps have HSPF ratings as high as 9.0, and geothermal heat pumps have HSPFs over 10.0. The HSPF averages the performance of heating equipment for a typical winter in the United States, so the actual efficiency will vary in different climates.

Type of Treatment

Table 7-6 Economic Analysis of Heat Pumps*

Incremental

Incremental

Energy Savings

Installed

($/yr)

Costs ($)

Annual Rate of Return

Incremental Mortgage Costs ($/yr)

SEER 11 (3 tons)--Compared to SEER 10

57

SEER 13 (3 tons)--Compared to SEER 11

243

SEER 11 (5 tons)--Compared to SEER 10

85

SEER 13 (5 tons)--Compared to SEER 11

365

Ground-Coupled (3 tons)

358

525

12.6%

46

1,057

27.5%

95

675

16.6%

59

1,175

36.0%

103

3,000

14.6%

264

*For Atlanta, GA.

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.urnace Equipment
Furnaces burn fuels such as natural gas, propane, and fuel oil to produce heat and provide warm, comfortable indoor air during cold weather in winter. They come in a variety of efficiencies. The comparative economics between heat pumps and furnaces depend on the type of fuel burned, its price, the home's design, and the outdoor climate. In general, moderately efficient natural gas furnaces with central air conditioning and electric, air-source heat pumps have similar installation and operating costs.
.urnace operation
Furnaces require oxygen for combustion and extra air to vent exhaust gases. Most furnaces are non-direct vent units--they use the surrounding air for combustion. Others, known as direct vent or uncoupled furnaces, bring combustion air into the burner area via sealed inlets that extend to outside air.
Direct vent furnaces can be installed within the conditioned area of a home since they do not rely on inside air for safe operation. Non-direct vent furnaces must receive adequate outside air for combustion and exhaust venting. The primary concern with nondirect vent units is that a malfunctioning heater may allow flue gases, which could contain poisonous carbon monoxide, into the area around the furnace. If there are leaks in the return system, or air leaks between the furnace area and living space, carbon monoxide could enter habitable areas and cause potentially severe health problems.
Most new furnaces have forced draft exhaust systems, meaning a blower propels exhaust gases out the flue to the outdoors. Atmospheric furnaces, which have no forced draft fan, are not as common due to federal efficiency requirements. However, some furnace manufacturers have been able to achieve the efficiency requirements in atmospheric units.
Atmospheric furnaces should be isolated from the conditioned space. Those units located in well ventilated crawl spaces and attics usually have plenty of combustion air and encounter no problem venting exhaust gases to the outside.
However, units located in closets or mechanical rooms inside the home, or in relatively tight crawl spaces and basements, may have problems. Furnace mechanical rooms must be well sealed from the other rooms of the home. The walls, both interior and

exterior, should be insulated. Two outside-air ducts sized for the specific furnace should be installed from outside into the room, one opening near the floor and another near the ceiling, or as otherwise specified in your locality's gas code.
Measures of efficiency for furnaces

The efficiency of a gas furnace is measured by the Annual Fuel Utilization Efficiency (AFUE), a rating which takes into consideration losses from pilot lights, start-up, and stopping. The minimum AFUE for most furnaces is now 78%, with efficiencies ranging up to 97% for furnaces with condensing heat exchangers.
Unlike SEER and HSPF ratings, the AFUE does not consider the unit's electricity use for fans and blowers. These can vary by over $50 annually.
An AFUE rating of 78% means that for every $1.00 worth of fuel used by the unit, approximately $.78 worth of usable heat is produced. The remaining $.22 worth of energy is lost as waste heat and exhaust up the flue. Efficiency is highest if the furnace operates

.igure 7-5 Sealed Mechanical Room Design

Screened high and low ventilation ducts into
mechanical room

Ventilate d attic

Insulated and sealed walls
between mechanical room
and home

Mechanical room access door is solid (non-louvered) with weatherstripping and a tight threshoold.

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for longer periods of time. Oversized units run intermittently, reducing efficiencies up to 15 percent.
Furnaces with AFUEs of 78 to 87% include components such as electronic ignitions, efficient heat exchangers, better intake air controls, and induced draft blowers to exhaust combustion products.
Models with efficiencies over 90%, commonly called condensing furnaces, include special secondary heat exchangers that actually cool flue gases until they partially condense, so that heat losses up the flue are virtually eliminated. A drain line must be connected to the flue to catch condensate. One advantage of the cooler exhaust gas is that the flue can be made of plastic pipe rather than metal and can be vented horizontally through a side wall.
There are a variety of condensing furnaces available. Some rely primarily on the secondary heat exchanger to increase efficiency, while others, such as the pulse furnace, have revamped the entire combustion process.
A pulse furnace achieves efficiencies over 90% using a spark plug to explode gases, sending a shock wave out an exhaust tailpipe. The wave creates suction to draw in more gas through one-way flapper valves, and the process repeats. Once such a furnace warms up, the spark plug is not needed because the heat of combustion will ignite the next batch of gas. The biggest potential problem is noise, so make sure the furnace is supplied with a good muffler, and do not install the exhaust pipe where any potential noise will be annoying.
Because of the wide variety of condensing furnaces on the market, compare prices, warranties, and service. Also, compare the economics carefully with those of moderate efficiency units. Condensing units may have longer paybacks than expected for energy efficient homes due to reduced heating loads.
Integrated Space and Water Heating

Gas-fired integrated systems
One type of integrated space and water heater system uses a quick recovery, high efficiency gas water heater to provide 140F water that provides space heating and hot water. Heating needs are met by pumping hot water from the water heater to a heating coil in the air handling unit.
Household air passing through ductwork connected to this coil is heated to between 110 and 120F. The water, cooled to about 120F by the air, returns from the heating coil to the integrated water heater for reheating. The air handler can also incorporate a cooling coil for air conditioning. The economics of these units can be quite favorable; however, it is often difficult to obtain an objective comparison between integrated systems and more conventional space and water heating equipment. Table 7-7 compares several options for a typical home.
.igure 7-6 Integrated Space and Water
Heating System

Supply ducts
Cooling coil
Blower
Heating coil with pump to water heater
Hot water for space heating Hot water for household needs

Return duct
Incoming cold water

An integrated space heating and domestic water heating unit provides a single, multipurpose system. The American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) has developed standards by which to evaluate such systems, as well as methods of measuring the efficiency of integrated systems with either space heating or water heating as their primary purpose.

High recovery gas water heater

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Type of Treatment

Table 7-7

Economic Analysis of Gas .urnaces*

Incremental

Incremental

Energy Savings ($/yr)

Installed Costs ($)

AFUE .80 (36,000 Btuh) Compared to AFUE .78

12

100

AFUE .93 (36,000 Btuh) Compared to AFUE .80

61

826

AFUE .80 (60,000 Btuh) Compared to AFUE .78

18

150

AFUE .93 (60,000 Btuh) Compared to AFUE .80

92

836

Integrated Gas Space and Water Heating

32

200

(.80 AFUE, 36,000 Btuh)

Compared to AFUE .78 with standard water heater

Integrated Gas Space and Water Heating

99

(.93 AFUE, 36,000 Btuh)

Compared to above integrated system

1,200

Annual Rate of Return 14.6%
8.4%
14.6%
12.6%
18.6%
9.1%

*For Atlanta, GA.

Incremental Mortgage Costs ($/yr) 9
73
13
74
18
106

Some advantages of integrated systems are:
s They can save floor space, as some air handling units mount to the wall or within the wall cavity above the water heater tank.
s They may have lower installed costs-- only one gas hook-up and a single flue are required.
s They often have a more efficient water heater than standard homes.
Another integrated approach uses a central boiler to provide space and water heating. Typically, the boiler can provide hot water even in nonheating seasons more efficiently than standard water heaters. However, the greater initial cost of this type of system may limit its use to families with high hot water demands.

Electric integrated systems
There are several products that use a central heat pump for water heating, space heating and air conditioning. These integrated units are available in both air-source and geothermal models.
To be a viable choice, integrated systems should: s Have a proven track record in the field. s Cost about the same, if not less, than comparable heating and hot water systems. s Provide at least a five-year warranty. s Be properly sized for both the heating and hot water load.
Make sure the unit is not substantially more expensive than a separate energy efficient heat pump and electric water heater . Units within $1,500 may provide favorable economic returns. The SEER of the unit should exceed 10.0.

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Wood Heating

Wood can be a thrifty alternative to conventional heating sources. However, if the homeowner must purchase wood fuel, the savings will diminish. Wood heating also requires work, and a fire-safe installation is essential.
Although there are wood-burning furnaces designed for homes, most homeowners interested in wood heating use a fireplace or wood heater--either free-standing stove or fireplace insert. Fireplaces and wood heaters are primarily space heaters. They radiate heat to people and objects close by and, to a lesser degree, heat the surrounding air.
Like other fuel-burning equipment, fireplaces and wood heaters need air for combustion and must vent exhaust products to the outside. In standard construction, air infiltration provides the necessary combustion air. However, in energy efficient homes, the sources of air infiltration are greatly reduced so special measures to supply outside combustion air must be provided.
An energy efficient fireplace must have a direct vent that brings air from outside the home to the firebox. The vent should be designed so that it remains clear of ashes, wood, and other materials when a fire is burning. It should be located toward the front of the firebox and have a damper or lid that prevents infiltration when the fireplace is not in use.

Table 7-8 Typical Wood Heating Savings ($/year)

Size of Home (sq ft) 1,200

Back-up Heating Efficiency Moderate * High**

1,800

Moderate High

2,400

Moderate High

3,200

Moderate High

% of Heating Needs Supplied 25% 50% 75% 100% 56 112 167 223 48 97 145 193
80 160 240 320 69 139 208 277
105 209 314 418 91 181 272 362
137 274 411 548 119 237 356 475

* Moderate efficiency units: Gas with AFUE of .78 to .80/ Heat pumps with HSPF of 6.8 to 7.4
** High efficiency units: Gas with AFUE over .90/ Heat pumps with HSPF over 7.5

.igure 7-7 Efficient Wood Heater Design
Rated flue properly installed
Flue damper
Radiant surfaces
Secondary combustion chamber
Catalytic device to aid combustion
Tight-fitting doors
Outside combustion air
In addition to an outside source of combustion air, a fireplace should have a tight-fitting flue damper and glass doors to further reduce infiltration. The flue damper should be opened before lighting a fire and closed after combustion is complete. The glass doors can be opened to let heat radiate to people near the fire and then closed as the fire dies to minimize room air being drawn up the chimney.
Some fireplace designs provide a means of heating room air by circulating it around the firebox where it is heated and then passed back into the house. These systems are more efficient than standard fireplaces.
Homeowners serious about using wood as a heat source should use a high efficiency wood heater, such as an airtight wood stove. As with fireplaces, wood heaters in energy efficient homes should have an outside source of combustion air. In fact, even standard houses may not have adequate infiltration levels to maintain proper combustion and venting for a wood heater.
To ensure safety, select a wood heater designed to supply its own outside combustion air. These units are required by code in manufactured housing and are usually sold by businesses supplying wood heaters and fireplaces. The wood heater should also be properly sized for the home. Many energy efficient homes have small heating loads, so large or even moderatesized wood heaters may produce too much heat.

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Unvented .uel-.ired Heaters
Unvented heaters that burn natural gas, propane, kerosene, or other fuels are not recommended. While these devices usually operate without problems, the consequences of a malfunction are life-threatening-- they can exhaust carbon monoxide directly into household air. They also can cause serious moisture problems inside the home.
Most devices come equipped with alarms designed to detect air quality problems. However, many experts question putting a family at any risk of carbon monoxide poisoning--they see no rationale for bringing these units into a home. A wide variety of efficient, vented space heaters is available.
Examples of unvented units to avoid include: s Vent-free gas fireplaces--use sealed combustion, direct vent units instead. s Room space heaters--choose forced draft, direct-vent models instead.
.igure 7-8 Unvented and Direct Vent Heaters
UNVENTED HEATER
Exhaust gases (including water vapor and carbon monoxide, usually
in small concentrations) Combustion air
(from interior of home)
DIRECT VENT HEATER
Exhaust gases to outside
Combustion air (from exterior)

Ventilation and Indoor Air Quality
All houses need ventilation to remove stale interior air and excessive moisture and to provide oxygen for the inhabitants. There has been considerable concern recently about how much ventilation is required to maintain the quality of air in homes. While it is difficult to gauge the severity of indoor air quality problems, most experts agree that the solution is not to build an inefficient, "leaky" home.
Research studies show that standard houses are as likely to have indoor air quality problems as energy efficient ones. While opening and closing windows offers one way to control outside air for ventilation, this strategy is rarely useful on a regular, year-round basis (consult the window chapter for more information). Most building researchers believe that no house is so leaky that the occupants can be relieved of concern about indoor air quality. They recommend mechanical ventilation systems for all houses.
The amount of ventilation required depends on the number of occupants and their lifestyle, as well as the design of the home. The ASHRAE standard, "Ventilation for Acceptable Indoor Air Quality" (ASHRAE 621989) recommends that houses have 0.35 air changes per hour (ach.)
Older, drafty houses can have infiltration rates of 1.0 to 2.5 ach. Standard homes built today are tighter and usually have rates of from 0.5 to 1.0 ach. New, energy efficient homes may have 0.35 ach or less.
The problem is that infiltration is neither continuous nor constant; it is unpredictable, and rates for all houses vary. For example, infiltration is greater during cold, windy periods and can be quite low during hot weather. Thus, pollutants may accumulate during periods of calm weather even in drafty houses. These homes will also have many days when excessive infiltration provides too much ventilation, causing discomfort, high energy bills, and possible deterioration of the building envelope.
Concerns about indoor air quality are leading more and more homeowners to install controlled ventilation systems for providing a reliable source of fresh air. The simplest approach is to provide spot ventilation of bathrooms and kitchens to control moisture. Nearly all exhaust fans in standard construction are ineffective -- a prime contributor to interior moisture problems in Georgia homes. Bath and kitchen exhaust fans should vent to the outside--not just into an attic or crawl space.

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General guidelines call for providing a minimum of 50 cubic feet per minute (cfm) of air flow for baths and 100 cfm for kitchens. Manufacturers should supply a cfm rating for any exhaust fan.
The cfm rating typically assumes the fan is working against an air pressure resistance of 0.1 inch of water--the resistance provided by about 15 feet of straight, smooth metal duct. In practice, most fans are vented with flexible duct that provides much more resistance. Some fans are also rated at pressures of 0.25 to 0.30 inches of water-- the resistance found in most installations. Most ventilation experts suggest choosing a fan based on this rating.
While larger fans cost more, they are usually better constructed and therefore last longer and run quieter. The level of noise for a fan is rated by sones. Choose a fan with a sone rating of 2.0 or lower. Top quality models are often below 0.5 sones.
Many ceiling- or wall-mounted exhaust fans can be adapted as "in-line" blowers located outside of the living area, such as in an attic or basement. Manufacturers also offer in-line fans to vent a single bath or kitchen, or multiple rooms. Distancing the in-line fan from the living area lessens noise problems.
While improving spot ventilation will certainly help control moisture problems, it may not provide adequate ventilation for the entire home. A whole house ventilation system can exhaust air

from the kitchen, all baths, and perhaps the living area or bedrooms.
Whole house ventilation systems usually have large single fans located in the attic or basement. Ductwork extends to rooms requiring ventilation. These units typically have two-speed motors. The low speed setting gives continuous ventilation--usually 10 cfm per person or 0.35 ACH. The high speed setting can quickly vent moisture or odors.
Removing Radon
In addition to ventilation within the home, ventilating from below the foundation will help remove radon and other soil gases such as moisture before they have a chance to enter the home in the first place. It is more cost-effective to include these radonresistant techniques while building a home, rather than retrofitting an existing home. A typical installation during construction will cost the homeowner roughly $50 to $300, whereas retrofitting an existing home can cost up to $2,000. In addition, no operating costs are associated with this passively vented system. If elevated radon levels are found in the home, a fan can be added easily to make it active (see sidebar on page 102).
Figure 7-11 shows the basics of radon resistant construction for crawlspaces and slabs/basement foundation types.

.igure 7-9 Ventilation with Spot .ans

.igure 7-10 In-Line Ventilation .ans

Spot fan
Air drawn in through inlet vents
Air drawn in through air leaks

In-line ventilation
fan

Outlet vent

Inlet vents to other rooms

Inlet vents

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Passive and active radon resistant construction
Passive concept: a perforated "T" fitting is attached to a vertical plastic vent stack that penetrates the roof. The "T" is buried in the gravel under the foundation slab and gases can slowly percolate through the "T" and out the stack.
Active concept: if unacceptable levels of radon are discovered once the homeowners test, inform them that a fan can be added to generate suction to pull gases out through the stack.
s Slab-on-grade or basement
Use a 4- to 6-inch gravel base. Install continuous layer of 6-mil polyethylene. Stub in "T" below polyethylene that protrudes
through polyethylene and extends above poured floor height. Pour slab or basement floor. Seal slab joints with caulk. s Crawl space
Install sealed, continuous layer of 6-mil polyethylene.
Install "T" below polyethylene that protrudes through polyethylene.
.igure 7-11 Radon Resistant Construction

s All foundations
Install a vertical 3-inch PVC pipe from the foundation to the roof through an interior wall.
Connect the "T" to the vertical 3-inch PVC pipe for passive mitigation.
Have electrician stub-in junction box in attic. Label PVC pipe " RADON" so that future
plumbing work will not be tied into the stack.
What is radon? Radon is a cancer-causing, radioactive gas that is found in soils all over the United States. Although you can't see, smell or taste radon, it can become concentrated at dangerous levels in any building--homes, offices, and schools. But people are most likely to get the greatest exposure at home because that is where most time is spent.
Testing for radon.
After building a radon-resistant home, it is still recommended to test the home for elevated radon levels. Lowcost "do-it-yourself" radon test kits can be obtained through the mail, in hardware stores and other retail outlets, and possibly from your local government. If desired, a trained contractor can be hired to do the testing. Make certain that they are NEHA-certified.
What if high levels are found?
With the basics of a radon mitigation system already installed, it is relatively inexpensive and easy for a homeowner to make it active. Adding an in-line fan rated for continuous operation is a relatively simple "do-it-yourself" project that will ensure the safe removal of radon from beneath your home.
See Appendix 4 for contact information regarding radon.

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Supplying outside air from air leaks
The air vented from the home by exhaust fans must be replaced by outside air --either through air leakage or a controlled inlet. Relying on air leaks requires no extra equipment; however, the occupant has little control over the air entry points. Plus, many of the air leaks come from undesirable locations, such as crawl spaces or attics. If the home is airtight, the ventilation fans will not be able to pull in enough outside air to balance the air being exhausted. It will generate a negative pressure in the home, which may cause

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increased wear on fan motors. Plus, the exhaust fans may threaten air quality by pulling exhaust gases from flues and chimneys back into the home.
Supplying outside air from inlet vents
Providing fresh outside air through inlet vents is another option. These vents can often be purchased from energy specialty outlets by mail order. They are usually located in exterior walls. The amount of air they allow into the home can be controlled manually or by humidity sensors.
Locate inlet vents where they will not create uncomfortable drafts. They are often installed in bedroom closets with louvered doors or high on exterior walls.
Supplying outside air via ducted make-up air
Outside air can also be drawn into and distributed through the home via the ducts for a forced-air heating and cooling system. This type of system usually has an automatically controlled outside air damper in the return duct system.
The blower for the ventilation system is either the air handler for the heating and cooling system or a smaller unit that is strictly designed to provide ventilation air. A slight disadvantage of using the HVAC blower is that incoming ventilation air may have sufficient velocity to affect comfort during very cold weather.
The return ductwork for the heating and cooling system may be connected to a small outside air duct that has a damper which opens when the ventilation fan operates. The resulting reduced air flow should not adversely affect comfort. Special controls are available to ensure that the air handler runs a certain percentage of every hour, thus fresh air is drawn in on a regular basis.
Dehumidification-Ventilation Systems
Georgia homes are often more humid than desired. A combined dehumidification-ventilation system can bring in fresh, but humid outdoor air, remove moisture, and supply it to the home. These systems can also filter incoming air. Because these systems require an additional mechanical device--a dehumidifier installed on the air supply duct--they should be designed for the specific needs of the home.

Heat Recovery Ventilators
Air-to-air heat exchangers, or heat recovery ventilators (HRV), typically have separate duct systems that draw in outside air for ventilation and distribute fresh air throughout the house. Winter heat from stale room air is "exchanged" to the cooler incoming air. Some models, called enthalpy heat exchangers, can also recapture cooling energy in summer by exchanging moisture between exhaust and supply air.
While energy experts have questioned the value of the heat saved in Georgia homes for the $400 to $1,500 cost for an HRV, recent studies on enthalpy units indicate their dehumidification benefit in summer offers an advantage over ventilation-only systems. The value of any heat recovery ventilation system should not be determined solely on the cost of recovered energy --the controlled ventilation and improved quality of the indoor environment must be considered as well.
.igure 7-12 .resh Air/Dehumidification Strategies
Introducing fresh air through the return system creates a positive pressure in the building.

950 cfm RETURN

1000 cfm SUPPLY

Wall cap with insect screen
and filter
50 cfm

Filter Modulating or Swing Shut-off Damper Damper

Air Handler

A dehumidification-ventilation unit does an excellent job of dehumidifying and filtering the outside air.

50 - 100 cfm

Filter

Filter APD Unit

Air Handler

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Heating, Ventilation, Air Conditioning (HVAC)

SAMPLE VENTILATION PLANS
Design 1: Upgraded Spot Ventilation
This relatively simple and inexpensive whole house ventilation system integrates spot ventilation using bathroom and kitchen exhaust fans with an upgraded exhaust fan (usually 100 to 150 cfm) in a centrally located bathroom. When the fan operates, outside air is drawn through inlets in closets with louvered doors. The fan is controlled by a timer set to provide ventilation at regular intervals. Interior doors are undercut to allow air flow to the central exhaust fan. The fan must be a long-life, high-quality unit that operates quietly. In addition to the automatic ventilation provided by this system, occupants can turn on all exhaust fans manually as needed.
Design 2: Whole House Ventilation System
This whole house ventilation system uses a centralized two-speed exhaust fan to draw air from the kitchen, bath, laundry, and living area. The blower is controlled by a timer. The system should provide approximately 0.35 ach on low speed and 1.0 ach on high speed. Outside air is supplied by a separate dampered duct connected to the return air system. When the exhaust fan operates, the outside air damper opens and allows air to be drawn into the house through the forced-air ductwork.
Design 3: Heat Recovery Ventilation (HRV) System
An enthalpy air-to-air heat exchanger draws fresh outside air through a duct into the heat exchange equipment and recaptures heating or cooling energy from stale room air as it is being exhausted. The system also dries incoming humid air in summer--a particular benefit in the Southeast. Fresh air flows into the house via a separate duct system, which should be sealed as tightly as the HVAC ductwork. Room air can either be ducted to the exchanger from several rooms or a single source. Some HRV units can be wallmounted in the living area, while others are designed for utility rooms or basements.

Spot fans

Upgraded exhaust
fan

Outside air inlet

Central exhaust
fan

Dampered outside air duct

Central heating and cooling system

Stale room air return ducts

Heat recovery ventilator

Exhaust air outlet
Fresh air inlet

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Duct Design and Sealing

8. Duct Design and Sealing

The Problem of Duct Leakage
Studies conducted throughout the country have found that poorly sealed ductwork is often the most prevalent and yet easily solved problem in new construction. Duct leakage contributes 10 to 30% of heating and cooling loads in many homes. In addition, duct leakage can lessen comfort and endanger health and safety.
Locating ducts in conditioned space eliminates many problems with leakage. They are often installed in chases framed air passageways situated behind the ceiling or wall finish. However, these chases are often connected more directly to unconditioned space than interior space. Therefore, it is important to seal these areas completely from unconditioned spaces.
The heating and cooling contractor should use proper materials when sealing ductwork--in particular, duct sealing mastic. Duct insulation does not provide an airtight seal. To ensure ducts are tight, have your HVAC contractor conduct a duct leakage test.
The Georgia Energy Code requires that duct systems are installed as tightly as possible. In particular, mastic and mesh tape must be used to seal leaks.
Duct Leaks and Air Leakage
Forced-air heating and cooling systems should be balanced--the amount of air delivered through the supply ducts should be equal to that drawn through the return ducts. If the two volumes of air are

unequal, then the pressure of the house can be affected. Pressure imbalances can increase air leakage into or out of rooms in the home.
Pressure imbalances can create dangerous air quality in homes including:
s Potential backdrafting of combustion appliances such as fireplaces, wood stoves and gas burners.
s Increasing air leakage from the crawl space to the home, which may draw in dust, radon, mold, and humidity.
s Pulling pollutants into the air handling system via return leaks.
Typical causes and concerns of pressure imbalances, addressed more fully in Chapter 3, include:
s HVAC systems with excessive supply leaks can cause homes to become depressurized, which may cause backdrafting of combustion appliances in the home.
s HVAC systems with excessive return leaks can cause homes to become pressurized and create negative pressures around the air handling unit. The negative pressures may cause combustion appliances near the air handling unit to backdraft.
s Homes with central returns can have pressure imbalances when the interior doors to individual rooms are closed. The rooms having supply registers and no returns become pressurized, while the areas with central returns become depressurized. Often the

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Duct Design and Sealing

returns are open to living rooms with fireplaces or combustion appliances. When these spaces become sufficiently depressurized, the flues will backdraft.
s Tighter homes with effective exhaust fans, such as kitchen vent hoods, clothes dryers, and attic ventilation fans, may experience negative pressures whenever these ventilation devices are operating.
Sealing Air Distribution Systems
Duct leakage should be eliminated. In standard construction, many duct seams are not sealed or are poorly sealed with ineffective materials such as cloth "duct tape," unrated aluminum tape, or similar products with lower quality adhesives not designed to provide an airtight seal over the life of the home. Use

only the following products for sealing the components of the air distribution system:
s Duct sealing mastic with fiberglass mesh tape--highly preferred--may add $20 to $55 to the cost of a $5,000 system, but will provide a lifetime, airtight seal.
s High quality caulking or foam sealant.
Note: Aluminum UL-181 A or B tape may be used for assembling fibrous duct board, but it must be installed properly to be effective. The duct surface must be clean of oil and dirt, and the tape must fully adhere to the duct with no wrinkles. A squeegee must be used to remove air bubbles from beneath the taped surface. UL-181 tape costs only $4 to $5 more than "silver tape," which has an inferior adhesive.

TESTING FOR DUCT LEAKAGE

The best method to ensure airtight ducts is to pressure test the entire duct system, including all boot connections, duct runs, plenums, and air handler cabinet. Much like a pressure test required for plumbing, ductwork can be tested during construction so that problems can be easily corrected.

In most test procedures, a technician temporarily seals the ducts by taping over the supply registers and return grilles. Then, the ducts are pressurized to a given pressure--usually 25 Pascals. This pressure is comparable to the pressure the ducts experience when the air handler operates.
The ducts are usually tested for tightness using a duct testing fan. Measuring the airflow through the fan gives an estimate of the air leakage through unsealed seams in the ductwork.

Pressure gauge
Duct testing fan
Fan control switch

Some energy efficiency programs require that the cubic feet per minute of duct leakage measured at a 25 Pascal pressure (CFM25) be less than 3% of the floor area of the house. For example, a 2,000-square-foot house should have less than 60 CFM25 of duct leakage.
Another test is to use a blower door (described in Chapter 3) and a duct testing fan together to measure duct leakage after construction is complete. This procedure gives the most accurate measurement of duct leakage to the outside of the home. A duct leakage test can usually be done in about one hour for an average sized home.

Registers sealed with tape
Duct Test on Return Grille

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Proper sealing and insulation of the ductwork in unconditioned areas requires careful attention to detail and extra time on the part of the heating and air conditioning contractor. The cost of this extra time is well worth the substantial savings on energy costs, improved comfort, and better air quality that an airtight duct system offers.
The easiest answer to the question of where to seal air distribution systems is "everywhere." A list of the key locations is as follows:
High priority leaks
s Disconnected components, including takeoffs that are not fully inserted, plenums or ducts that have been dislodged, tears in flexduct, and strained connections between ductwork (visible when the duct bends where there is no elbow).
s The connections between the air handling unit and the supply and return plenums.
s All of the seams in the air handling unit, plenums, and rectangular ductwork--look particularly underneath components and in any other tight areas. Also seal the holes for the refrigerant, thermostat, and condensate lines. Use tape rather than mastic to seal the seams in the panels of the air handling unit so they can be removed during servicing. After completion of service and maintenance work, such as filter changing, make sure the seams are retaped.

s The return takeoffs, elbows, boots, and other connections. If the return is built into an interior wall, all connections and seams must be sealed carefully. Look especially for unsealed areas around site-built materials.
s The takeoffs from the main supply plenum or trunk line.
s Any framing in the building used as ductwork, such as a "panned" joist in which sheet metal nailed to floor joists provides a space for conditioned air to flow. It is preferable to avoid using framing as a part of the duct system.
s The connections near the supply registers --between the branch ductwork and the boot, the boot and the register, the seams of the elbows, and all other potential leaks in this area.
Moderate priority leaks
s The joints between sections of the branch ductwork.
Low priority leaks
s Longitudinal seams in round metal ductwork.

.igure 8-1 Sealing .lex-duct Collar with Mastic

Attach flex-duct to take-off collar
with strap

Apply mastic to seal flex-duct to collar and collar
to plenum

Builders Guide to Energy Efficient Homes in Georgia

Pull insulation and outer liner over sealed take-off; strap outer
liner in place
107

Duct Design and Sealing
.igure 8-2 Disconnected Ducts Are High Priorities

.igure 8-3 Duct Leaks in Inside Spaces

yyy;;;y;y;yyyyyyyyyyyy;;;;;;;;;;;;y;y;yyyyyyyyyy;;;;;;;;;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;

Dislodged supply duct
Ducts can become disconnected during initial installation, maintenance, or even normal operation. They should be checked periodically for problems.

;yyy;;;yy;;;;;;;;;;;;yyyyyyyyyyy;y;yy;;;;;;;;;;;;yyyyyyyyyyy;y;yy;;y;y;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy;;yy
Although this supply duct is theoretically in conditioned space, the supply leaks pressurize the band joist area and air leaks to the outside. The best solution--seal all duct
leaks and all building envelope air leaks

.igure 8-4 Seal All Leaks in Air Handling Unit

Disconnection at boot

Sometimes, disconnected ducts can be hidden behind the insulation. Look for kinks or curves where there is no elbow.

Many air handling cabinets come from the factory with leaks, which should be sealed with duct-sealing mastic.
Removable panels should be sealed with tape.

Removable panel sealed with tape

Mastic

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Builders Guide to Energy Efficient Homes in Georgia

.igure 8-5 Shelf-Mounted Systems Without Returns

Duct Design and Sealing
.igure 8-6 Seal All Leaky Takeoffs
Apply mastic

Non-ducted returns can severely depressurize mechanical room closets, not only sapping the system's efficiency, but also creating ideal conditions for backdrafting and other air
quality problems. Seal all leaks with mastic or caulk.
Separate air for combustion

Leaky return takeoff pulls in surrounding
air

Seal leaky filter rack with rated aluminum tape

.igure 8-7 Sealing Leaky Boots

Room return
air

Mastic

The return should be connected to the home via a well sealed duct. All holes from the mechanical room closet
to other spaces should be completely sealed.

Use mastic to completely seal all leaky seams and holes. Use mesh tape with mastic to cover cracks over 1/8-inch
wide.

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Duct Design and Sealing

Duct Design
Duct Materials
The three most common types of duct material used in home construction are metal, fiberglass duct board, and flex-duct. Both metal and fiberglass duct board are rigid and installed in pieces, while flex-duct comes in long sections.
Flex-duct is usually installed in a single, continuous piece between the register and plenum box, or plenum box and air handler. While it has fewer seams to seal, it is important that the soft lining material not be torn. The flex-duct must also not be pinched or constricted. Long flex-duct runs can severely restrict air flow, so they must be designed and installed carefully. Flex-duct takeoffs, while often airtight in appearance, can have substantial leakage and should be sealed with mastic.
Round and rectangular metal duct must be sealed with mastic and insulated during installation. It is important to seal the seams first, because the insulation does not stop air leaks. Rectangular metal duct used for plenums and larger trunk duct runs is often insulated with duct liner, a high density material that should be at least 1-inch thick.
Metal ducts often use fiberglass insulation having an attached metal foil vapor retarder. The duct insulation should be at least R-6, and the vapor retarder should be installed to the outside of the insulation-- facing away from the duct. The seams in the insulation are usually stapled together around the duct and then taped. Duct insulation in homes at least two-years old provides great clues about duct leakage --when the insulation is removed, the lines of dirt in the fiberglass often show where air leakage has occurred.
Sizing and layout
The size and layout of the ductwork affects the efficiency of the heating and cooling system and comfort levels in the home. The proper duct size depends on:
s The estimated heating and cooling load for each room in the house.
s The length, type, and shape of the duct.
s The operating characteristics of the HVAC system (such as the pressure, temperature, and fan speed).

.igure 8-8 Types of Ductwork
Round metal pipe
Ductboard
Flex-duct
The lower temperature of the heated air delivered by a heat pump affects the placement of the registers. A heat pump usually supplies heated air between 90F and 110F. At these temperatures, air leaving registers may feel cool. It is important that they are placed so as to avoid blowing air directly onto people. Fuel-fired furnaces typically deliver heated air at temperatures between 110F and 140F, 40F to 70F greater than room temperature, so placement of the supply registers is less important to maintain comfort.
In standard duct placement and design, supply registers are almost always located on outside walls under or above windows, and return registers are placed towards the interior, typically in a central hallway.
Some builders of energy efficient homes have found little difference in temperature between interior areas and exterior walls because of the extra energy features. Locating the supply registers on exterior walls is not as necessary to maintain comfort. These builders are able to trim both labor and material costs for ductwork by locating both supply and return ducts near the core of the house.
In standard duct design, virtually all supply ducts are 6-inch flex-duct or round metal pipe. Most standard designs have only one return for each floor.
The above rules work for some homes, but can create operating problems for others, including:

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s Too much heating and cooling supplied to small rooms, such as bathrooms and bedrooms with only one exterior wall.
s Inadequate airflow, and thus, insufficient heating and cooling in rooms located at a distance from the airhandler.
s Overpressurization of rooms when interior doors are closed.
The heating and cooling industry has comprehensive methods to size supply and return ductwork properly. These procedures are described fully in Manual D, Duct Design published by the Air Conditioning Contractors' Association.
Unfortunately, few residences have ductwork designed via Manual D. Most HVAC contractors use 6inch ductwork for every supply register in the home. The primary "design" is determining, usually via intuition, how many registers should be installed in each room.
Figure 8-10 shows the size ductwork Manual D would specify for a small home. The design is vastly different than the typical, all 6-inch system. The

advantage of proper design is that each room receives air flow proportionate to its heating and cooling load, thus increasing overall comfort and efficiency.
The following recommendations, while no substitute for a Manual D calculation, should improve system performance:
s If two rooms have similar orientation, window area, and insulation characteristics, but one room is considerably farther from the air handling unit than the other, consider increasing the size of the ductwork going to the farthest room.
s Bonus rooms over garages often need additional or larger supplies.
s Rooms with large window areas may warrant an extra supply duct, regardless of the room size.
s Likewise, large rooms with few windows, only one exterior wall, well insulated floor, and conditioned space above may need only one small duct.

.igure 8-9 Comparison of Air .low in Different 6-inch Ducts

130 cfm

110 cfm

Straight, short, round metal duct

Straight, short, flex-duct

Long, convoluted, round metal duct

100cfm Long, convoluted, flex-duct

75 cfm

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Duct Design and Sealing

CHECKING SYSTEM AIR FLOW
Use this simple form to check the ductwork for proper sizing: Step 1: Find the system's cooling capacity in tons. Step 2: Multiply the tonnage by 400 to get the desired total air flow in cubic feet per minute (cfm) =
400 x ________ tons = ___________ cfm total Step 3: Check the supply air flow
a. Determine the number of supply registers connected to 4", 6", 8", and 10" branch ducts . b. Fill in column 2 in the chart below. Then multiply the number of ducts by the air flow and put the result in Column 4. Add the flows in Column 4. If the total is within 10% of the actual air flow (from Step 2), the supply ductwork is probably adequate.

1. Branch Duct Size 4" 6" 8" 10"
Total Air Flow

2. Number of Supply Registers

3. Air Flow per Register (cfm)
50 100 200 400

4. Duct Air Flow (cfm) Step 2 x Step 3
cfm

Step 4: Check the return air velocity a. Measure the total area of all return grilles = ________square inches b. Multiply the total area in 4a by 70% = _______square inches c. Divide the answer to b by 144 to get square feet of area = ________ square feet d. Write the total air flow here = ________ cfm (total cfm in chart above) e. Divide the air flow in 4d by the area in 4c to get the estimated return air velocity: airflow _______ / area ________ = ________ ft/minute If the velocity is over 650 ft/ minute, add a return or increase the size of a return. Example: Home with 2.5 ton system, one 4-inch, eight 6-inch, and one 8-inch branch supply ducts. Step 1: 2.5 tons Step 2: 400 x 2.5 = 1,000 cfm Step 3:

1. Branch Duct Size 4" 6" 8" 10"
Total Air Flow

2. Number of Supply Registers
1 8 1 0

3. Air Flow per Register (cfm)
50 100 200 400

4. Duct Air Flow (cfm) Step 2 x Step 3
50 800 200

1,050

cfm

Since 1,050 cfm is within 10% of system air flow, there should be enough supply ducts.

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.igure 8-10 Duct Design Using Manual D (In standard duct installation, all supply registers would be 6 inches in diameter, and there would be a single 14-inch to 16-inch return.)

6"

4"

3"

3"

6"

8"

7" return

14" return
5"

9"

12" return
6" 3"
7" Air handling
unit 3"
8"

Builders Guide to Energy Efficient Homes in Georgia

Ductwork Summary

Supply

Return

Size
3" 4" 5" 6" 7" 8" 9"

Number
4 1 1 3 1 2 1

Size 7" 12" 14"

Number 1 1 1

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Duct Design and Sealing
Notes:

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Domestic Water Heating

9. Domestic Water Heating

Energy costs for water heating can be as great as
those for heating or cooling a house. An average family of four in Georgia will spend about $300 to $400 annually for electric or propane water heating and $125 to $200 for natural gas. However, it is easy to cut those bills dramatically with conservation measures and water heating alternatives.
Energy Conservation for Water Heating
No matter what type of energy source is used to heat water, be certain to take advantage of the savings from conservation measures:
s Lower the temperature setting on the water heater to 120F.
Saves energy.
Reduces the risk of injury from scalding.
Provides plenty of hot water.
If hotter temperatures are needed for dish washing, select dishwashers with booster heaters.
s Wrap the outside of the water heater tank with an insulation jacket.
Simple to install--payback less than 1 year.
Do not cover the relief or drain valve.
For gas water heaters, do not block the air inlet to the burner or the flue vent on the top.

s Insulate first four feet of all pipes connected to unit.
s Low-flow showerheads provide about a 1-year payback and are required by the Georgia Energy Code. Well designed fixtures deliver water at 2.5 or fewer gallons per minute and still provide plenty of force.
s Heat traps (Figure 9-2) keep hot water from circulating freely out of the water heater.
s Low-flow aerators on sink and lavatory faucets.
Save on energy bills.
Kitchen sink may need a higher volume flow faucet for filling pots and pans more quickly.
.igure 9-1 Water Use in Typical Homes
(In Gallons per Day)

Toilet 41

Lawn & garden 3
Car washing 1
Household cleaning 3
Washing clothes 4 Drinking 5 Kitchen 6

Showers 22
Bathing 15

Source: "Water delivery crisis as severe as drought," Atlanta Constitution, June 21, 1988, page 10A.

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Domestic Water Heating

Table 9-1 Energy .actors for High Efficiency
Water Heaters*

Size of Unit (gallons)

Energy Factor Range

Gas-Fired 30 40 50

0.54 - 0.64 0.61 - 0.86 0.73 - 0.83

Electric Resistance 30 40 50
60-66 80

0.91 - 0.95 0.91 - 0.94 0.90 - 0.94 0.90 - 0.94 0.89 - 0.92

*Source: Alex Wilson and John Morrill. Consumer Guide to Home Energy Savings. American Council for an Energy Efficient Economy. Washington, DC. 1995.

Selecting an Efficient Water Heater
Water heaters come in a range of efficiencies, warranties, and fuel sources. Their efficiencies are measured by a rating known as the energy factor (EF).
Gas Water Heaters
Higher efficiency gas water heaters have energy factors over 0.80. In addition to variations in insulation, gas water heater efficiency is also affected by burner design, the shape of the flue baffles which slow the hot exhaust gases down to increase heat transfer to the water, and the amount of surface area between the flue gases and the water.
Higher efficiency gas water heaters have blowers for venting and delivery of combustion air. A number of these units can be vented out of the sidewall of the home rather than the roof because of the forced air blower.

Heat traps reduce heat
loss

.igure 9-2 Insulating Jackets for Electric and Gas Water Heaters

Hot

Cold

Hot

Cold

Insulate first four feet of all metal pipes extending out of water heater

Electric Water Heater

Gas Water Heater

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Domestic Water Heating

Fuel-fired water heaters should be located in unconditioned spaces that are isolated in terms of pressure and air leakage from the living area. Examples include crawl spaces, attics, and unconditioned basements.
If fuel-fired water heaters are located in interior spaces, such as interior mechanical rooms connected to conditioned spaces or laundry rooms, they should include provisions for outside combustion air, such as a direct-vent unit. They have a double flue pipe that includes both an intake for combustion air and a flue for exhaust gases.
More sophisticated energy features found on high efficiency furnaces, such as electronic ignition, flue dampers, and condensing heat exchangers, are being introduced into domestic water heaters.

When shopping for a water heater, use the Energy Guide sticker to compare the estimated annual energy cost for a specific water heater with comparable models. The estimated annual cost shown in bold print on the sticker uses the national average cost of fuel, which could differ significantly in your area.
Electric Water Heaters
For electric water heaters, higher efficiency units range up to 0.97. Often, the additional cost of a high efficiency unit is quite low compared to the savings. Because of the high cost of electric water heating, more efficient options such as heat recovery units, heat pump water heaters, and solar water heaters should always be considered.

Heat recovery units

.igure 9-3 Combustion Closet for .uel-.ired Water Heater

Screened high and low combustion air ducts into closet - extend 6" above insulation in attic

High Low

Vented exhaust pipe through roof

A heat recovery unit, also called a desuperheater, recovers excess heat from an air conditioner or heat pump to provide "free" hot water. The heat is captured from the refrigerant line between the outside condenser and the inside equipment (see description of how air conditioners work in Chapter 7). A heat exchanger mounted on this line extracts heat from the superheated, high pressure, refrigerant gas, which is hot enough to be able to lose some heat and still not begin to condense into a liquid.

Seal gas and plumbing penetrations through walls

Insulated walls
Insulated water heater

Door closes against solid threshold

Bottom plate sealed

Solid (non-louvered) door with weatherstripping

During the summer, the desuperheater can usually provide 100 percent of the hot water needs of a family and improve the efficiency of the air conditioner or heat pump. In the spring and fall, with no heating or cooling, the desuperheater is ineffective. In the winter, if connected to a heat pump, the desuperheater can still provide hot water more efficiently than a conventional electric water heater. The energy savings from a desuperheater connected to a central air conditioner depend on how often the air conditioner is used. Savings are typically 20 to 40% on water heating bills.
The size and efficiency of the water heater and cooling equipment will affect the performance of a desuperheater. Combining desuperheaters with new higher efficiency air conditioners or heat pumps, which have lower refrigerant temperatures, can reduce the energy savings. The HVAC system should be at least 2 tons in size to be used effectively with a desuperheater. Desuperheaters range in cost from $550 to $750 and save $50 to $180 annually. Before installing a unit, make sure it will not void warranties on mechanical equipment.

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Heat pump water heaters
Heat pump water heaters operate at about twice the efficiency of standard electric water heaters. They cost $700 to $1,200 installed and can save $100 to $200 each year.
Heat pump water heaters use surrounding air as a heat source. As they extract heat from the air, they provide some dehumidification and cooling--about 40,000 Btu per day for a typical house. While the cool dry air is an advantage in summer, it is detrimental in winter. It is best to locate the unit in an unconditioned area, such as an unheated basement, where the cooling effect will not cause winter discomfort or higher heating bills. The area must stay above 45F for the unit to operate properly. To avoid damaging the equipment, never install a heat pump water heater in areas where the temperature drops below freezing.
Heat pump water heaters are sold either as separate cabinets which are connected to a conventional
.igure 9-4 Heat Pump Water Heaters

water heater or as packages complete with the hot water storage tank. When operating, they are about as loud as an air conditioner, so do not locate them where noise will be a problem.
Solar Water Heaters
For homes that use a large amount of hot water and receive full sun year-round, solar water heaters may be economical. Most solar water heaters operate by preheating water for a standard water heater. Normally, gas or electric water heaters bring incoming cold water to a desired temperature of about 120F. A solar water heater uses sunlight to preheat cold water and stores it, often at temperatures well above 120F.
If the solar-heated water is hot enough, the standard water heater does not need to add more heat. If the water is cooler than needed, the standard water heater will operate as a backup to increase the temperature. Thus, the temperature or availability of hot water is never affected. Of course, even when the solar-heated water is at temperatures below 120F, the backup unit will use less energy than it would to heat incoming cold water.
A variety of solar water heaters is available commercially, most of which should last 15 years or

Hot water out

Warm water in

.igure 9-5 Active Solar Water Heating Systems
Collector

Standard water heater
118

Hot water to house

Pump turned on by control system

Storage tank/ back-up water
heater
Incoming water supply (cold)

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Domestic Water Heating

longer. They are divided into three categories: active, thermosiphon, and batch. In active and thermosiphon water heaters, solar panels or collectors trap the sun's heat. Water or other fluid running through the collectors absorbs heat and increases in temperature. The liquid then travels to a storage tank where the heat it gains is stored.
Active systems use electric pumps to move the water from the collectors to the storage tank. Thermosiphon water heaters require no outside power because they use the natural tendency of water to rise as its temperature increases to push water from the collectors to the storage tank, which must be located higher than the collectors.
Some solar water heaters use a single, large storage tank that has a backup source of water heating. Other systems use a standard water heater as a backup and a separate solar storage tank. Active and thermosiphon systems cost from $1,500 to $5,000 and supply up to 70 percent of a family's annual hot water needs.
The tilt angle of the glazing--the angle between the glazing and the horizon--should be within 15 degrees of the latitude. For Georgia, the tilt angle can be between 18 and 50 degrees. The best tilt angle for a year-round solar device, such as a solar water heater, is 35 to 45 degrees. For solar collectors used only for winter heating, tilt angles can be raised to between 50 and 60 degrees.
Solar water heaters must be protected from freezing. Active and thermosiphon systems use nonfreezing fluids or automatic drain systems to prevent freezing.
Batch water heaters, also called breadbox water heaters, are simpler than active or thermosiphon systems. However, they provide less hot water, usually about 15 to 40 percent of a family's yearly demand. Batch water heaters combine the collector and storage tank in one box. The box has insulated sides, a clear cover, and one or more tanks inside. In some cases, large tubes are used instead of tanks. A batch water heater can typically store 30 to 50 gallons of hot water.
On a sunny day, sunlight travels through the glazing of the batch unit and strikes the tanks, which are flat black in color. In most cases, the tanks are covered with a special selective surface coating that readily absorbs sunlight, but reduces heat loss from the tank. When the tanks absorb the sun's energy, the water inside heats up. Local water pressure pushes the solar-heated water into the regular water heater

.igure 9-6 Batch Solar Water Heating System

Incoming water supply (cold)

Hot water to house

Batch water heater with tank inside

Back-up water heater

whenever a fixture or appliance, such as a shower or dishwasher, is drawing hot water.
Batch heaters are manufactured and sold commercially. Prices range from about $800 to $1,500. However, because of the simplicity of the design, some people build their own.
The collectors for any type of solar water heater should be located as close as possible to the water heater tank to minimize the connecting piping. The glazing should face within 45 degrees of due south.
Collectors are usually located on the roof, but they can be attached to supports on the side of a house or on the ground. Because batch water heaters combine collectors, storage tanks, and water they are heavy. Adequate structural support must be provided when they are located on the roof.
Water inside the tanks of a batch water heater will only freeze on bitterly cold nights. However, the water in the pipes that connect the batch heater to the inside can freeze at temperatures around 32F. A special freeze prevention drip valve should be used on a batch water heater.
Solar water heating can provide year round savings. Households that use a large amount of hot water and can adapt the time when hot water is used to match when it is available will benefit the most. Savings will be greatest if laundry, dishes, and bathing are done between noon and early evening--after the sun has heated the water stored in the tank.

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Domestic Water Heating

Instantaneous Water Heaters
Instantaneous water heaters use higher capacity electric coils or gas burners to heat cold water only when there is a need for hot water. They save energy in two ways: they have no storage tank so there is no need to keep stored water continuously warm, and gas-fired units usually heat water more efficiently than gas tank-type water heaters. Conventional water heaters keep 30 to 50 gallons of water at a constant temperature--24 hours a day.
Instantaneous units must be sized carefully for their planned use. A small unit may provide heating for only one faucet or appliance at a time, so a higher capacity model or several units are generally needed to provide hot water for conventional residential uses. By eliminating the standby losses and increasing efficiency, instantaneous water heaters may save 10 to 20 percent of a household's usual water heating bill.
The units range in cost from $250 to $800. In general, instantaneous water heaters are not particularly cost-effective investments. It is usually more economical to use conservation measures such as low-flow showerheads, insulated tank jackets and reduced thermostat settings to lower standby losses, and to install conventional, high efficiency water heaters.

.igure 9-7 Instantaneous Water Heater

Heat from fuel combustion or electric elements

Flue if fuel-fired heater

Heat exchanger

Cold water in

Hot water out

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Appliances and Lighting

10. Appliances and Lighting

Energy Efficient Appliances
Heating, cooling, and hot water are usually the biggest portion of energy needs in Georgia homes. However, the cost of operating major appliances is significant. In the average home, energy bills range from $200 to $400 each year to run refrigerators and freezers, clothes washers and dryers, ranges and ovens, and other appliances.
While most new appliances offer a wide variety of features, many models are not designed to be energy efficient. When choosing appliances, it is important to consider their operating costs--how much energy they require to run--as well as the purchase price and the various features and conveniences they offer.
Appliances which operate efficiently may cost more to buy, but the energy savings they provide make them a good investment. For example, running a standard refrigerator over its life of 15 to 20 years costs about three times as much as its purchase price. An energy efficient model can save hundreds of dollars over the life of the appliance. Table 10-1 shows typical annual energy costs for a variety of appliances.
In addition to saving money on operating costs, energy efficient appliances give off less waste heat than standard models. Therefore, they help keep rooms inside the house cooler during warm weather.
The National Appliance Energy Conservation Act

(NAECA), which upgraded the efficiencies of heating, cooling, and hot water systems, also required improvements in appliance efficiencies. The last round

Table 10-1 Typical Energy Costs for Appliances

Appliance

Average High Efficiency 10-Year Model ($/yr) Model ($/yr) Savings

Refrigerator

56

(manual defrost)

36

$200

Refrigerator/freezer 96 (frost free)

56

400

Freezer (frost free) 108

60

480

Electric range

48

40

80

Gas range

36

28

80

Electric clothes

56

dryer

44

120

Gas clothes dryer 24

20

40

Dishwasher*

56

36

200

Color Television

20

8

120

Lighting

60

28

320

*Includes cost of water heating.
Source: Adapted from "Saving Energy and Money with Home Appliances," by the Massachusetts Audubon Society and the American Council for an Energy Efficient Economy.

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Appliances and Lighting

of refrigerator standards took effect in January 1, 1993. As a result, a typical refrigerator of today uses less than 800 kilowatt-hours (Kwh) per year--less than half of that for a typical 1973 model.
EnergyGuide Label
To compare the energy usage of an appliance, use the EnergyGuide label. Federal law requires that manufacturers display this label on all new refrigerators, freezers, water heaters, dishwashers, clothes washers, and room air conditioners. EnergyGuide labels are not currently required on kitchen ranges, microwave ovens, clothes dryers, demand-type water heaters, and portable space heaters.
The large number on the EnergyGuide label tells how much that appliance will cost to operate each year based on an estimate of the amount of energy used and an average national energy costs. The rating for a particular model is shown on a line scale that compares its energy cost against the model with the lowest and highest annual energy costs. Much like the federal miles per gallon ratings for automobiles, the actual amount of energy used and its cost will vary according to local prices and each family's life-style.
.igure 10-1 EnergyGuide Label

The EnergyGuide label also provides the name of the manufacturer, model number, type of appliance, and capacity. It has a yearly cost table that shows a range of energy rates and the total annual cost to operate that particular appliance at each rate. Use exact energy rates from local utilities to estimate operating costs for the appliance.
ENERGY STAR Appliances
The U.S. EPA has done some of the research for consumers and has labeled certain appliances with the ENERGY STAR logo that meet their criteria for energy efficiency. The ENERGY STAR label may be found on clothes washers, refrigerators, dishwashers, and room air conditioners. An appliance receives the ENERGY STAR rating if it is significantly more energy efficient than the minimum government standards, as determined by standard testing procedures. The amount by which an appliance must exceed the minimum standards is different for each product rated and depends on available technology. ENERGY STAR rated products are always among the most efficient available today.
Appliance Shopping Checklist
All appliances
s Use EnergyGuide label to help select unit. Find the savings in operating costs for the more efficient appliance. Divide the savings per year into the extra purchase price to get the payback period. Paybacks of less than five years are generally attractive.
Refrigerators
s The most efficient models are in the 16 to 20cubic foot range.
s Side-by-side refrigerator/freezers use more energy than similarly sized models with freezers on top.
s Features such as automatic icemakers and through-the-door dispensers add somewhat to energy use.

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Appliances and Lighting

s Units that are more square, rather than rectangular, also save energy, but may not be as convenient to use.
s Manual defrost units save considerably more than frost-free units, but create more work for the homeowner.
s Look for a power-saving switch that turns off a condensation-prevention heater. Keep this switch off unless the unit experiences significant condensation.
s A new generation of refrigerators not using chlorofluorocarbons (CFCs) exceeds the minimum standards of NAECA by about 30%--the result of the electric utility funded Super Efficient Refrigerator Program (SERP).
s Try to install the refrigerator in a cooler location--in particular, it should not receive direct sunlight.
s The refrigerator should operate between 40F and 38F, and the freezer should be 0F to 5F. Correct temperatures that are outside of this range.
Dishwashers
s Water heating accounts for about 80% of energy use.
s Models that use less water need less energy-- older units used 8 to 14 gallons per wash cycle compared to the mid-1994 range of 7 to 10 gallons.
s Should have light, medium, and heavy cycle options--water use for one dishwasher was 7.5 gallons for a light cycle, 11 gallons for medium, and 13 gallons for heavy.
s Should have an energy saving "air dry" or "no-heat dry" switch.
s Choose a unit that contains a supplemental or booster water heater; then set your water heater to 120 F.
s Minimize pre-rinsing of dishes unless necessary; always rinse in cold water.
s Wash only full loads.

Clothes washing machines
s Choose a machine that offers several wash and rinse cycles and several sizes of loads.
s Front-loading models feature faster spin cycles, which dry clothes better, and use less water than top-loading models; in addition, front-loading models usually get clothes cleaner.
Clothes dryers
s Energy-saving switches and models that detect "dryness" and shut off automatically offer considerable energy savings.
some units have moisture sensors in the drum, which save about 15% over standard dryers
others have a temperature sensor in the dryer exhaust, which saves about 10% over standard units
s If clothes that usually need ironing are removed while slightly damp, they can be hung up to save on dryer and ironing energy use.
Cooking
s Convection ovens are about 1/3 more efficient than standard ovens.
s Electric cooktops with ceramic glass covers are more efficient than coil or disk electric stoves; induction elements, which use electromagnetic energy to heat the pan, are the most efficient.
s Be careful with large kitchen exhaust fans. While they are important, oversized units can create considerable negative pressures in tight homes and may cause backdrafting of combustion appliances.

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Appliances and Lighting

.igure 10-2 Energy Efficiencies of Lights
(Lumens per Watt)

Standard Incandescent Tungsten Halogen Halogen Infrared Reflecting Mercury Vapor Compact Fluorescent (5-26 watts)

Compact Fluorescent (27-55 watts)

Metal Halide Compact Metal Halide

White Sodium

High Pressure Sodium

0 10 20 30 40 50 60 70 80 90 100 110
Lamp Plus Ballast Lumens/Watt

Lighting
Standard incandescent bulbs are the most common lighting source for homes. However, incandescent lamps are quite inefficient. They convert only 10 percent of the electricity to lighting. The rest produces waste heat. The lighting industry has responded to the need for energy efficiency with a wide range of excellent products. The most notable of these options are:
1. Compact fluorescents that use thin tubes and require only 5 to 29 watts of electricity to provide as much light as standard incandescent lamps. These products can also provide the same quality of light as incandescent lamps.
2. Lower wattage fluorescent tubes, along with efficient electronic ballasts, can reduce the energy needed by a standard 2-lamp, 4-foot fixture from 92 watts to about 60 watts. There are many products available with a high color rendition index (CRI), which measures the ability of a lamp to illuminate colors accurately.

3. High pressure sodium and metal halide lamps, mainly intended for exterior use in residences, are four to six times more efficient than standard exterior lighting lamps.
There is great opportunity for originality and ingenuity in residential lighting design. A home combines more functions and needs than most other buildings, yet energy efficient lighting can be achieved at minimal cost. Of course the needs of each home must be considered individually, but certain conservation measures are applicable to all home designs, including:
s Energy efficient fixtures and lamps for areas of high continuous lighting use, such as the kitchen, sitting areas, and outside the home for safety and security.
s Local task lighting for specific activities such as working at a desk, on a kitchen counter, or in a workshop.
s Accent lighting so that the overall level of lighting in an area can be reduced.
s Timers and light-sensitive switches for exterior lighting.

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Appliances and Lighting

s Daylighting--using sunlight as the light source in areas normally occupied during the day.
s Solid-state dimmers and multilevel switches which allow variable lighting levels.
The amount of light a lamp provides is measured in lumens. The electrical energy used to provide that light is measured in watts. The lighting level depends on the efficiency of the light source in converting watts to lumens and the ability of the lighting fixture to effectively distribute the light. High efficiency lamps and lighting fixtures reduce wattage requirements but still provide desired lighting levels.
The efficiency--called the efficacy--of a lamp is measured in lumens of light produced per watt of electricity consumed. Table 10-2 provides comparative efficacies of different lamp types.
In designing a lighting plan, consult with knowledgeable professionals about optimum lighting levels and different types of fixtures and lamps. Table 10-3 shows sizing guidelines for fluorescent lighting systems.
When choosing lighting fixtures, consider the long term energy costs of the fixture as well as the purchase price. Energy efficient lighting alternatives reduce waste heat in summer, thereby saving money on cooling costs and increasing comfort levels. In

Table 10-3 .luorescent Lighting Guidelines

Type of Room Size of Room Amount of

Light Needed

(Watts)

Living room,

under 150 sq ft 40 to 60

bedrooms, family, 150 to 250 sq ft 60 to 80

or recreation room over 250 sq ft .33 watt/sq ft

Kitchen, laundry, or workshop

75 sq ft

55 to 70

75 to 120 sq ft 60 to 80

over 120 sq ft .75 watt/sq ft

addition, they last considerably longer than standard incandescent lamps.
Table 10-5 shows the purchase and operating costs of a number of lighting options. The different alternatives are grouped by lumen output so lamps for similar uses can be compared.
For example, a standard 75-watt incandescent lamp costs $54 for electricity and bulb replacements over 10,000 hours of operation. Compare that to a new, compact fluorescent lamp, which lasts 10,000 hours compared to 1,000 for the incandescent, and costs only $30 to purchase and operate.

Table 10-4 Standard Versus Energy Efficient Residential Lighting

Standard Lighting Design

Room

Type*

Watts Hours/ Kwh/

day year

Kitchen

I

150

8 438

Living

I

150

6 328

Dining

I

75

5 137

Bathrooms (2)

I

200

4 292

Hallway

I

150

10 545

Bedrooms (3)

I

225

4 328

Laundry/ Utility

I

100

4 146

Closets (5)

I

300

1 110

Porch

I

100

12 438

Exterior Floodlight

I

360

12 1,577

Total Annual Electricity Use (Kwh)

4,339

Annual Lighting Cost ($ @ $.075/Kwh)

325

Estimated Extra Cost for Energy Efficient Lighting

Payback Period

Rate of Return on Investment

Energy Efficient Design

Extra Type* Watts Kwh/

Cost ($)

year

30

F

60

175

5

H

135 296

-

I

75

137

-

I

200 292

30

F

60

219

30

F

90

131

25

F

30

44

-

I

300 110

15

F

30

131

100 HPS 150 657

2,192

164

$210

1.3 years

60%

* I=incandescent; F=fluorescent; H=halogen; HPS=high-pressure sodium

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Appliances and Lighting

Table 10-5 Purchase and Operating Costs of Different Lighting Products

Wattage

Typical Purchase Cost ($)

Lumens

Incandescent and Fluorescent

Standard

60

0.50

870

Energy saving (Halogen) 52

0.79

800

Compact fluorescent

15

13.00

720

Standard

75

Energy saving (Halogen) 67

Compact fluorescent

18

Compact fluorescent

20

0.50 0.79 18.00 20.00

1,210 1,130 1,100 1,200

Standard

100

Energy saving (Halogen) 90

Compact fluorescent 23-27

0.77 0.79 20-25

1,750 1,620 Comparable

Torchiere Fixtures

Halogen

300

Compact Fluorescent

78

with three 26-watt lamps

20

4,000

80

4,200

Room Lighting

Incandescent fixture with 180 three, 60-watt lamps
Standard fluorescent fixture 92 with two, 40-watt lamps
Above fixture with 32-watt 60 lamps/electronic ballast

30

2,610

30

6,300

42

5,500

Exterior Fixtures (assuming 4 outdoor fixtures)

Standard PAR lamp (4 lamps/ fixture)

1,800

Tungsten-halogen (4 lamps/ fixture)

1,080

Mercury Vapor

400

(1 lamp/ fixture)

Metal Halide

250

(1 lamp/ fixture) High Pressure Sodium 200
(1 lamp/ fixture)

120

20,880

144

21,600

65

23,000

100

20,500

90

22,000

Rated Life (Hours)

Efficacy (Lumens/
Watt)

1,000

15

1,000

15

10,000

48

1,000

16

1,000

17

10,000

61

10,000

60

750

17

750

18

10,000

64

2,000

13

10,000

54

1,000

15

20,000

68

20,000

102

2,000

12

2,000

20

24,000

57

10,000

82

24,000

110

*Electricity cost @ $0.08/kWh

Energy Cost* for 10,000 hours ($)
48 42 12 60 54 14 16 80 72 20
240 62
144
74
48
1,440
864
320 200 160

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Passive Solar Homes - Designs for Today

11. Passive Solar Homes Designs for Today

Passive solar homes capture both the beauty of
the outside world and the heat coming in from the sun. They are designed with the local climate in mind--to use temperature, humidity, wind, and solar radiation to determine the site, orientation, floor plan, and overall building layout, and materials. The key features of passive solar homes are:
s Energy conservation measures--energy efficiency is always the first step in designing a passive solar home. For guidance, use details from a comprehensive energy package, such as those in Chapter 1.
s Glass concentrated on the south-- south windows let sunlight into the building in winter and can be shaded in summer. Lowemissivity coatings will reduce heat loss at night and heat gain in summer.
s Thermal storage mass--tile-covered slab floors, masonry walls, and water-filled containers store solar heat and save energy all year.
s Window shading--overhangs, blinds, shade screens, curtains, and landscaping shade unwanted sunlight in summer.
s Ventilation--natural breezes, ceiling fans, whole house fans, and space fans keep the house more comfortable during warmer weather.
Current trends in housing, such as expansive glass areas, daylighting, sunrooms, great rooms, tile floors, fireplaces, and open floor plans, fit well into passive solar designs. Effective designs will reduce heating and cooling bills and provide greater comfort.

Basic Design Guidelines
A cardinal rule in passive solar design is to set one's sights properly--don't expect more than the sun can deliver. The Southeastern climate has cool, relatively cloudy winters and hot, humid, relatively sunny summers. Many well-designed passive solar homes in Georgia provide their owners with low energy bills and year-round comfort, as well as natural daylight and visual connection with the outdoors. However, poorly designed passive solar homes may actually have uncomfortable temperature swings both in summer and in winter.
Whether considering how to include passive solar features in a new home by adapting a conventional home plan, or designing an entirely new plan, the following design ideas should be considered. Rooms with large expanses of glass should include thermal storage mass.
s Day-use rooms--Breakfast rooms, sunrooms, and playrooms work well on the south side of the house. They should adjoin rooms that are used frequently to take full advantage of solar heating.
s Frequently-used rooms (morning to bedtime)--Family rooms, kitchens, dens, and dining rooms work well on the south side. Be conscious of potential problems with glare from sunlight through large expanses of windows.
s Sunspaces--Passive solar rooms can be isolated from the house. In winter, the doors or windows between the house and the sunspace can be opened to let solar heat move into the

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Passive Solar Homes - Designs for Today
.igure 11-1 Passive Solar Room Planning
Night time rooms

Shading porch Shading porch

Activity rooms SOUTH

home. At night, the doors can be closed, and the sunspace buffers the home against the cold night air. In summer, sunspaces protect the home from outside heat gain--for best performance, they should not be air conditioned.
s Privacy rooms--Bathrooms and dressing rooms can be connected to solar-heated areas, but are not usually located on the south side since large windows are not desirable.
s Night-use rooms--Bedrooms are usually best on the north side, unless used often during the day (such as a study or children's bedroom). It is often difficult to fit thermal storage mass into bedrooms, and privacy needs may limit opportunities for installing large glass areas. However, some household members may prefer bedrooms filled with natural light which can use passive solar features effectively.

s Seldom-used rooms--Formal living rooms, dining rooms, and extra bedrooms are best on the north side, out of the traffic pattern and air flow.
s Buffer rooms--Unheated spaces such as closets, laundries, workshops, pantries, and garages work best against the north, east, or west exterior walls to protect the conditioned space from outside temperature extremes.
s Exterior covered areas--Porches and carports on the east and west provide summer shading. However, west-facing porches may be uncomfortable in the afternoon. Avoid porches on the south side, as they shade winter sunlight. South-facing decks on a second floor often shade glass expanses on the first floor. To allow solar gain, the decks should only be three to four-feet wide.

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Passive Solar Components
The most successful passive solar homes are simple. They combine energy conservation features, direct gain windows and sunspaces, adequate thermal storage mass in direct sunlight, open floor plans to promote natural convection of solar heat throughout the house, and effective natural cooling techniques. Although the design elements are basic, the specifications for each component are critical. Too much south-facing glazing, inadequate thermal mass, an unbalanced floor plan, and lack of shading and ventilation can create an energy loser--not a winner. The following guidelines should help ensure that the home design provides year-round comfort as well as low energy bills.
Passive Solar Windows
At a minimum, passive solar windows should be double-glazed and face within 20 degrees of due south. Avoid roof glass or skylights, as well as east and west windows, which cause overheating in summer and suffer heat loss at night during the winter. North windows are helpful for ventilation, daylight, aesthetics, and code requirements for emergency exits.
Low-emissivity windows will improve the performance of passive solar homes. They screen a small amount of sunlight during the day, but reduce nighttime heat loss and improve comfort. If a home has large areas of south glass, but little thermal storage mass, low-e glazing is highly recommended to help moderate temperature extremes. The savings provided by low-e glass can be as great in summer as in winter, depending on the window design and the home's location.
Proper design
The best passive solar homes combine energy conservation features, passive solar heating, and natural cooling. Table 11-1 shows examples of different combinations. Note that just adding more glass on the south side of a home, even with added mass, may not reduce annual energy bills due to higher summer cooling demands from the increased south window area.
Table 11-2 shows the savings from passive solar sunspaces. These rooms serve as practical, aesthetic buffers between outside temperature extremes and the interior rooms. In winter, the heat generated in a
Builders Guide to Energy Efficient Homes in Georgia

Passive Solar Homes - Designs for Today
.igure 11-2 Basic Passive Solar Designs
Direct Gain
South-facing windows allow sunlight directly into the living area where thermal storage mass captures the sun's energy.
Passive Solar Sunspace
Sunspaces--rooms that are independent of the home's heating and cooling system capture the sun's energy and transfer the heat generated to the house.
Thermal Storage Wall
Thermal storage walls store incoming solar heat and let it radiate into the living area.
Solar Air Collector
Solar air collectors absorb incoming solar energy, vent through the back of the air collector and transfer solar-heated air into the house.
129

Passive Solar Homes - Designs for Today

sunspace from incoming sunlight can significantly reduce heating bills.
Thermal Storage Mass
Thermal storage mass improves the energy performance of a home throughout the year by keeping interior temperatures from fluctuating greatly. The presence of thermal mass distinguishes a passive solar home from a sun-tempered design which has moderate amounts of glass but no mass.

Problems without thermal storage mass
A home with large expanses of south-facing windows and little thermal mass has problems such as:
s Uncomfortably warm on sunny winter days. s Uncomfortably cool on winter nights. s High midday temperatures in summer. s Higher heating and cooling bills than compa-
rable homes without as much glass area.

Table 111 Energy Bills in Direct Gain Homes*

Area (sq. ft.) South Glass Concrete Slab

RValues

Annual Energy Bills ($/yr)

Ceiling Wall Floor Windows Heating Cooling Total

Double-glazed Windows

Base Home

75

Example 1

180

Example 2

270

Example 3

360

Low-e Windows

Base Home

75

Example 1

180

Example 2

270

Example 3

360

0 720 1,080 1,440
0 720 1,080 1,440

30 15 13

1.8

30 15 13

1.8

30 15 13

1.8

30 15 13

1.8

30

15 13

3.3**

30

15 13

3.3**

30

15 13

3.3**

30 15 13 3.3**

212

231 443

147

192 339

127

210 337

108

229 337

165

210 375

114

176 290

99

185 284

84

194 278

Table 11-2 Energy Bills in Homes with Sunspaces*

With Sunspace, Low-e Windows

Example 1

180

Example 2

270

Example 3

360

720 1,080 1,440

30

15 13

3.3**

157

30

15 13

3.3**

141

30

15 13

3.3**

127

With Sunspace, Better House Insulation

Example 1

180

720

Example 2

270

1,080

Example 3

360

1,440

38 22 19 3.3***

80

38 22 19 3.3***

55

38 22 19 3.3***

39

* For an 1,800-square-foot home in Atlanta modeled using CALPAS 3. ** Low-e glass on south windows only; others have double glazing. *** Low-e glass on all windows.

114 271 125 266 137 264
112 192 123 178 136 175

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.igure 11-3 Spread Out Thermal Mass Surface

Passive Solar Homes - Designs for Today
.igure 11-4 Use .loor Coverings Wisely

dark color medium color light color

All sunlight hits mass surfaces

carpet vinyl no covering
Fraction of sunlight stored for colored floors

Properly designed passive solar homes should not overheat significantly during the day, and the heat they store helps to maintain temperatures above 60F on most winter nights. One misconception about passive solar homes is that they retain high temperatures (above 68F) for long periods of time. On nights when outside temperatures drop below 40F, passive homes may drop below 65F and need backup heating. However, they will require less heating than a conventional home.
Providing adequate thermal mass is usually the greatest challenge to the passive solar designer. The amount of mass needed is determined by the area of south-facing glazing and the location of the mass. Follow these guidelines to ensure an effective design.
Guideline 1: locate the thermal mass in direct sunlight.
Thermal mass installed where the sun can reach it directly is more effective than indirect mass placed where the sun's rays do not penetrate. Houses that rely on indirect storage need three to four times more thermal mass than those using direct storage.
Guideline 2: distribute the thermal mass.
Passive solar homes work better if the thermal mass is relatively thin and spread over a wide area. The surface area of the thermal mass should be at least 3 times, and preferably 6 times, greater than the area of the south windows. Slab floors that are 3 to 4 inches thick are more cost effective and work better than floors 6 to 12 inches thick.

Guideline 3: do not cover the thermal mass.
Figure 11-4 shows the effect of various floor coverings on the performance of passive solar homes with slab floors. Carpeting virtually eliminates savings from the passive solar elements. Masonry walls can have drywall finishes, but should not be covered by large wall hangings or lightweight paneling. The drywall should be attached directly to the mass wall, not to purlins fastened to the wall that create an undesirable insulating airspace between the drywall and the mass.
Guideline 4: select an appropriate mass color.
For best performance, finish mass floors with a dark color. A medium color can store 70 percent as much solar heat as a dark color, so it may be appropriate in some designs. A matte finish for the floor will reduce reflected sunlight, thus increasing the amount of heat captured by the mass and having the additional advantage of reducing glare. The color of interior mass walls does not significantly affect passive solar performance.
Guideline 5: insulate the thermal mass surfaces.
Chapter 5 on energy conservation measures shows techniques for insulating slab floors and masonry exterior walls. These measures should be followed to achieve the predicted energy savings.

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Passive Solar Homes - Designs for Today

Guideline 6: make thermal mass multipurpose.
To ensure their cost effectiveness, thermal mass elements should serve other purposes as well. Masonry thermal storage walls are one example of a passive solar design that is often cost prohibitive because the mass wall is only needed as thermal mass. On the other hand, tile-covered slab floors store heat, serve as structural elements, and provide a finished floor surface. Masonry interior walls provide structural support, divide rooms, and store heat.
Thermal Mass Patterns
Table 11-3 shows how the amount of thermal mass directly affects the savings produced by a passive solar home. Note that energy bills for a direct gain home with no thermal mass actually increase over a comparable energy efficient home with standard glass areas. Adding more thermal mass than is recommended increases energy savings but is often not cost effective.
Thermal mass can be incorporated into a passive solar room in many ways, from tile-covered floors to water-filled drums. When selecting thermal mass materials, consider the aesthetics, costs, and energy performance. Design options for thermal mass include:

s Slab-on-grade floors--used in most passive solar homes. Slab floors can be finished with tile, stone, or brick finish, can be stained, or can be scored into a tile-like pattern. They can be expensive to install on upper floors. Floors made of brick, brick paver, or thick tile also may be used.
s Exterior mass walls--walls composed of solid concrete, brick or stone and located on exterior walls. They must be exposed to sunlight and indoor air and insulated on the outside. They should not be covered with materials such as wood paneling or fabric that will block the flow of heat between the wall and the room. A mass wall can be covered with drywall if it is bonded directly to the masonry surface without creating an airspace.
s Interior mass walls--solid mass walls between interior rooms. Since they have living area on both sides, they can be up to 12 inches thick, although thinner 4- to 8-inch walls deliver heat to rooms adjacent to the passive solar areas more quickly. Masonry fireplaces that are several feet thick store heat but are not as effective as thinner mass walls with greater surface area. Since masonry is not a good insulator, keep fireplaces on interior walls.

Table 11-3 Heating Bills as a .unction of Thermal Mass

Amount of Thermal Mass
Passive solar house* with: No thermal storage mass recommended mass recommended mass Recommended mass 1- recommended mass

Heating Energy Demand
(Million Btu/yr)
44.3 31.5 29.2 28.0 24.5

Energy Savings
($/yr)
0 128 151 163 198

30-Year Discounted Savings ($)**
0 2,300 2,720 2,935 3,565

*For a 1,824-square-foot energy efficient home with 270 square feet of south-facing windows. **The 30-year discounted energy savings is the sum of the savings for each year discounted to the present.

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Passive Solar Homes - Designs for Today

s Water-filled containers--water stores heat twice as effectively as masonry on a volume basis and five times as effectively on a weight basis. However, water containers look unusual in most living areas. Since they store more heat per pound, less weight is required to store the same amount of solar heat, therefore they are easier to use in upstairs rooms. Commonly used water containers include fiberglass cylinders (containers 8 feet high by 1 foot in diameter hold 47 gallons) and 30- or 55-gallon metal drums. Metal containers should be treated with a rust inhibitor to extend their life.
s Hot tubs, saunas, and indoor pools--some homeowners have tried to use hot tubs, saunas, and indoor pools as thermal storage mass. In most cases, these forms of water storage do not work well. Also the desired water temperature for comfortable use of these amenities is hotter than the passive solar contribution can possibly achieve.
s Thermal storage walls--a solid masonry wall fronted by exterior double-glazed windows. Sometimes known as Trombe' walls, these designs are one of the least cost-effective passive solar options. They are expensive to build, and many researchers question whether the mass wall has sufficient time to warm between the periodic spells of cloudy weather experienced by most of the Southeast in the winter.
s Phase change materials--offer four to five times the storage capacity of water and 25 times that of masonry. PCMs store some heat as they increase in temperature, but most of their heat is stored when they change phases (melt). Each pound of phase change material absorbs as much heat when melting as 5 pounds of water does when increasing in temperature from 70 to 90F. The energy stored by the phase change is given up when the air in the room begins to cool and the phase change material solidifies. While potentially effective, PCM's are expensive and not readily available.

Estimating Passive Solar Saving
The following rules of thumb approximate the annual heating energy savings of passive solar homes:
s Each square foot of double-glazed southfacing window that is unshaded in the winter will save 40,000 to 60,000 Btu per year on a home's heating bill, if sufficient thermal mass exists.
s Low-emissivity glass will increase the savings 15 to 30 percent.
Thus, an energy efficient home with 200 square feet of passive solar windows and sufficient thermal storage mass could save 8 to 12 million Btu of energy on home heating bills each year. Movable insulation or low-e glass would save an additional 2 to 4 million Btu.
The Solar Savings Method is a more accurate method for calculating the energy saved by passive solar design. The approach, developed by Los Alamos National Laboratory, calculates the Solar Savings Fraction based on the heating load of the house (a measure of its potential to lose heat in winter) and the passive solar glass area, given that the house has proper amounts of thermal storage mass.
The following steps are based on the Solar Savings Method and can provide an estimate of the savings on heating offered by passive solar designs. The estimates require that a house have properly designed thermal storage mass and heat distribution. The home also should have natural cooling measures to prevent summer overheating. The Passive Solar Handbook, Volume III, published by the U.S. Department of Energy has detailed information on this procedure. Passive Solar Design Strategies: Guidelines for Home Builders, published by the Passive Solar Industries Council, has computational methods as well.

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133

Passive Solar Homes - Designs for Today
.igure 11-5 Thermal Mass Patterns

Direct gain--slab floor thermal mass

Direct gain--mass floor and rear masonry interior mass wall

Direct gain--mass floor and masonry walls on sides of rooms

Water wall

Sunspace--mass floor and wall 134

Direct gain sunspace (cannot be closed off from conditioned area)--mass floor and water thermal storage
Builders Guide to Energy Efficient Homes in Georgia

Passive Solar Homes - Designs for Today

Table 11-4 South Window Area for Passive Solar Homes
Recommended areas expressed as percentage of floor area*

Unshaded Overhang

Awning or Solar Screen

Solar Screen and Low-e Glass

Direct gain or water wall 0-5

Sunspace

5-10

5-12 5-20

5-16 5-25**

5-20 5-30

*For example, a 2,000-square-foot home should not have more than 100 square feet (.05 x 2,000) of unshaded, direct gain glass. If the direct gain area is shaded with an awning or solar screen, then its area can be increased to 16 percent of the floor area.

**If the area of south-facing glazing for a sunspace will exceed 20 percent of the floor area of the home, then it should be isolated from the rest of the house and not be air conditioned.

SOLAR SAVINGS ESTIMATOR
Step 1: Write the area of passive __________sq ft. solar windows

Step 2: Divide the area of the

__________

south-facing windows in

Step 1 by the heated floor

area of the house

Step 3: Locate the window multiplier in (Table 11-5)

________MMBtu per yr /sq ft

Step 4: Multiply the window area _______MMBtu/yr by the multiplier (Step 1 answer x Step 3 answer)

Step 5: Find the delivered cost of __________$/Btu energy for the heating system from Table 11-6

Step 6: Multiply the Step 4 savings $__________ by the energy cost in Step 5 to get annual heating savings

For example, a direct gain passive solar house in Atlanta has 1,920 square feet of living area and 288 square feet of south glazing. The south glass is thus 15 percent (288/1,920) of the floor area. The house has a standard natural gas furnace.

Step 1: Passive solar window area = 288 sq ft

Step 2: South window area as a

fraction of heated floor area = .15

Step 3: Window

multiplier (from Table 11-5) = .041

Step 4: Annual energy savings = 11.8 MMBtu/yr

Step 5: Cost of delivered energy = $7.7/MMBtu

Step 6: Annual dollar savings on

heating bills

= $91

When considering passive solar heating, don't forget the cooling season. Some passive solar homes in Georgia have had overheating problems. Careful designs avoid overheating and often save on summer cooling bills. Chapter 6 on windows and doors describes shading and ventilation measures.
Always remember that the south window area is only one component of an effective passive solar design. Thermal storage mass and summer overheating protection are critical as well.
Heat Distribution
It may be necessary to transfer solar-heated air from the south-facing rooms in a passive solar home to other rooms. Passive solar heating is simple in its operation. Any design to distribute the heat throughout the house should reflect this simplicity.
As air is warmed by the sun on the south side of the building, it rises, causing cooler air from the interior of the house to circulate to the south side--a process known as natural convection. Floor plans that have the south-facing rooms stepped down from the north side enhance convection. A stepped design also allows rooms on the south to be constructed with slab floors and rooms on the north to have framed floors.
Sunspace designs that have large glazing areas may generate sufficient heat to warrant a small blower or fan to transfer the heat into the rest of the house. A ceiling fan can be used at a low setting or a thermostatically controlled blower can be installed in the connecting wall. These forced ventilation measures may also improve heat distribution for direct gain designs. The key to moving air heated in a passive solar design is to move it slowly--fast-moving air at less than 90F can make people feel uncomfortable.

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135

Passive Solar Homes - Designs for Today

Table 115 Passive Solar Window Energy Savings Multiplier(MMBtu/year-square-foot)*

Design Feature Direct gain Direct gain, low-e glazing Sunspace Sunspace, low-e glazing Thermal storage wall
Design Feature Direct gain Direct gain, low-e glazing Sunspace Sunspace, low-e glazing Thermal storage wall

Atlanta
South Window Area as a Fraction of Living Area .050 .075 .100 .125 .150 .175 .200 .250 .058 .053 .048 .044 .041 .038 .036 n/a .076 .071 .067 .064 .061 .058 .055 n/a .076 .068 .061 .056 .052 .048 .045 .041 .097 .087 .078 .072 .066 .061 .057 .051 .072 .063 .056 .052 .048 .045 .043 n/a
Savannah .050 .075 .100 .125 .150 .175 .200 .250 .056 .051 .046 .043 .040 .037 .035 n/a .065 .061 .057 .053 .050 .046 .043 n/a .065 .058 .051 .046 .042 .039 .036 .032 .082 .072 .062 .056 .051 .047 .043 .037 .062 .055 .048 .044 .041 .038 .035 n/a

Design Feature Direct gain Direct gain, low-e glazing Sunspace Sunspace, low-e glazing Thermal storage wall

Macon .050 .075 .100 .125 .150 .175 .200 .250 .057 .052 .048 .045 .043 .040 .038 n/a .075 .069 .063 .060 .057 .050 .043 n/a .076 .061 .056 .052 .048 .045 .042 .037 .092 .081 .071 .065 .060 .055 .051 .045 .071 .062 .054 .050 .046 .043 .040 n/a

*The charts assume the house has full access to winter sunlight and contains properly designed thermal storage mass.
Source: Derived from charts in "Passive Solar Design Handbook, Volume 3: Passive Solar Design Analysis," edited by Robert Jones, published in July, 1992 by the U.S. Department of Energy as publication number DOE/CS-0127/3.

Table 116 Typical Delivered Cost of Energy for Atlanta
(June 1996)

Type of Fuel

Base Cost of Energy

($/unit)

($/MMBtu)

Natural gas Propane Fuel oil Electric heat pump Electric air conditioner

.60/therm 1.10/gallon .85/gallon
.06/kWh .085/kWh

6.00 12.00
6.25 17.60 24.90

Delivered Energy Cost ($/MMBtu)

Standard ($) Highly Energy

Efficient ($)

7.70

6.45

15.40

12.90

8.00

7.30

8.80

7.20

8.50

5.70

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Appendix 1 Mortgage Rate Tables

Appendix 1

Builders Guide to Energy Efficient Homes in Georgia

137

Appendix 1

The following tables show the monthly payment for principal and interest for a $1,000 loan at various interest rates and amortization periods. For example, a $50,000 loan at 15% with a 25-year amortization period will have monthly payments of $12.81 x 50 = $640.42. This table is useful in comparing different methods of financing construction loans and permanent mortgages and their effect on the economics of energy efficient construction techniques.

Interest Rate 5.00 5.25 5.50

5.75 6.00 6.25 6.50

6.75 7.00 7.25 7.50

7.75 8.00

1 Years of 2 Amortization 3
4 5 6 7 8 9 10 11 12 13 14 15 17 20 25 30

85.61 43.87 29.97 23.03 18.87 16.10 14.13 12.66 11.52 10.61
9.86 9.25 8.73 8.29 7.91 7.29 6.60 5.85 5.37

85.72 43.98 30.08 23.14 18.99 16.22 14.25 12.78 11.64 10.73
9.99 9.37 8.86 8.42 8.04 7.42 6.74 5.99 5.52

85.84 44.10 30.20 23.26 19.10 16.34 14.37 12.90 11.76 10.85 10.11
9.50 8.99 8.55 8.17 7.56 6.88 6.14 5.68

85.95 44.21 30.31 23.37 19.22 16.46 14.49 13.02 11.88 10.98 10.24
9.63 9.12 8.68 8.30 7.69 7.02 6.29 5.84

86.07 44.32 30.42 23.49 19.33 16.57 14.61 13.14 12.01 11.10 10.37
9.76 9.25 8.81 8.44 7.83 7.16 6.44 6.00

86.18 44.43 30.54 23.60 19.45 16.69 14.73 13.26 12.13 11.23 10.49
9.89 9.38 8.95 8.57 7.97 7.31 6.60 6.16

86.30 44.55 30.65 23.71 19.57 16.81 14.85 13.39 12.25 11.35 10.62 10.02 9.51
9.08 8.71 8.11 7.46 6.75 6.32

86.41 86.53 44.66 44.77 30.76 30.88 23.83 23.95 19.68 19.80 16.93 17.05 14.97 15.09 13.51 13.63 12.38 12.51 11.48 11.61 10.75 10.88 10.15 10.28 9.65 9.78
9.22 9.35 8.85 8.99 8.25 8.40 7.60 7.75 6.91 7.07 6.49 6.65

86.64 86.76 44.89 45.00 30.99 31.11 24.06 24.18 19.92 20.04 17.17 17.29 15.22 15.34 13.76 13.88 12.63 12.76 11.74 11.87 11.02 11.15 10.42 10.55 9.92 10.05
9.49 9.63 9.13 9.27 8.54 8.69 7.90 8.06 7.23 7.39 6.82 6.99

86.87 45.11 31.22 24.30 20.16 17.41 15.46 14.01 12.89 12.00 11.28 10.69 10.19
9.77 9.41 8.83 8.21 7.55 7.16

86.99 45.23 31.34 24.41 20.28 17.53 15.59 14.14 13.02 12.13 11.42 10.82 10.33
9.91 9.56 8.98 8.36 7.72 7.34

Interest Rate 8.25 8.50 8.75

9.00 9.25

9.50 9.75 10.00 10.25 10.50 10.75 11.00 11.25

1 2 Years of 3 Amortization 4 5 6 7 8 9 10 11 12 13 14 15 17 20 25 30

87.10 45.34 31.45 24.53 20.40 17.66 15.71 14.26 13.15 12.27 11.55 10.96 10.47 10.06
9.70 9.13 8.52 7.88 7.51

87.22 45.46 31.57 24.65 20.52 17.78 15.84 14.39 13.28 12.40 11.69 11.10 10.61 10.20
9.85 9.28 8.68 8.05 7.69

87.34 45.57 31.68 24.77 20.64 17.90 15.96 14.52 13.41 12.53 11.82 11.24 10.75 10.34
9.99 9.43 8.84 8.22 7.87

87.45 45.68 31.80 24.89 20.76 18.03 16.09 14.65 13.54 12.67 11.96 11.38 10.90 10.49 10.14
9.59 9.00 8.39 8.05

87.57 45.80 31.92 25.00 20.88 18.15 16.22 14.78 13.68 12.80 12.10 11.52 11.04 10.64 10.29
9.74 9.16 8.56 8.23

87.68 45.91 32.03 25.12 21.00 18.27 16.34 14.91 13.81 12.94 12.24 11.66 11.19 10.78 10.44
9.90 9.32 8.74 8.41

87.80 46.03 32.15 25.24 21.12 18.40 16.47 15.04 13.94 13.08 12.38 11.81 11.33 10.93 10.59 10.05
9.49 8.91 8.59

87.92 88.03 46.14 46.26 32.27 32.38 25.36 25.48 21.25 21.37 18.53 18.65 16.60 16.73 15.17 15.31 14.08 14.21 13.22 13.35 12.52 12.66 11.95 12.10 11.48 11.63 11.08 11.23 10.75 10.90 10.21 10.37
9.65 9.82 9.09 9.26 8.78 8.96

88.15 46.38 32.50 25.60 21.49 18.78 16.86 15.44 14.35 13.49 12.80 12.24 11.78 11.38 11.05 10.53
9.98 9.44 9.15

88.27 46.49 32.62 25.72 21.62 18.91 16.99 15.57 14.49 13.63 12.95 12.39 11.92 11.54 11.21 10.69 10.15
9.62 9.33

88.38 46.61 32.74 25.85 21.74 19.03 17.12 15.71 14.63 13.78 13.09 12.54 12.08 11.69 11.37 10.85 10.32
9.80 9.52

88.50 46.72 32.86 25.97 21.87 19.16 17.25 15.84 14.76 13.92 13.24 12.68 12.23 11.85 11.52 11.02 10.49
9.98 9.71

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Appendix 1

Interest Rate 11.50 11.75 12.00 12.25 12.50 12.75 13.00 13.25 13.50 13.75 14.00 14.25 14.50

Years of 1 Amortization 2
3 4 5 6 7 8 9 10 11 12 13 14 15 17 20 25 30

88.62 46.84 32.98 26.09 21.99 19.29 17.39 15.98 14.90 14.06 13.38 12.83 12.38 12.00 11.68 11.18 10.66 10.16
9.90

88.73 46.96 33.10 26.21 22.12 19.42 17.52 16.12 15.04 14.20 13.53 12.98 12.53 12.16 11.84 11.35 10.84 10.35 10.09

88.85 47.07 33.21 26.33 22.24 19.55 17.65 16.25 15.18 14.35 13.68 13.13 12.69 12.31 12.00 11.51 11.01 10.53 10.29

88.97 47.19 33.33 26.46 22.37 19.68 17.79 16.39 15.33 14.49 13.83 13.29 12.84 12.47 12.16 11.68 11.19 10.72 10.48

89.08 47.31 33.45 26.58 22.50 19.81 17.92 16.53 15.47 14.64 13.98 13.44 13.00 12.63 12.33 11.85 11.36 10.90 10.67

89.20 47.42 33.57 26.70 22.63 19.94 18.06 16.67 15.61 14.78 14.13 13.59 13.15 12.79 12.49 12.02 11.54 11.09 10.87

89.32 47.54 33.69 26.83 22.75 20.07 18.19 16.81 15.75 14.93 14.28 13.75 13.31 12.95 12.65 12.19 11.72 11.28 11.06

89.43 47.66 33.81 26.95 22.88 20.21 18.33 16.95 15.90 15.08 14.43 13.90 13.47 13.11 12.82 12.36 11.89 11.47 11.26

89.55 47.78 33.94 27.08 23.01 20.34 18.46 17.09 16.04 15.23 14.58 14.06 13.63 13.28 12.98 12.53 12.07 11.66 11.45

89.67 47.89 34.06 27.20 23.14 20.47 18.60 17.23 16.19 15.38 14.73 14.21 13.79 13.44 13.15 12.70 12.25 11.85 11.65

89.79 48.01 34.18 27.33 23.27 20.61 18.74 17.37 16.33 15.53 14.89 14.37 13.95 13.60 13.32 12.87 12.44 12.04 11.85

89.90 48.13 34.30 27.45 23.40 20.74 18.88 17.51 16.48 15.68 15.04 14.53 14.11 13.77 13.49 13.05 12.62 12.23 12.05

90.02 48.25 34.42 27.58 23.53 20.87 19.02 17.66 16.63 15.83 15.20 14.69 14.28 13.94 13.66 13.22 12.80 12.42 12.25

Interest Rate 14.75 15.00 15.25 15.50 15.75 16.00 16.25 16.50 16.75 17.00 17.25 17.50 17.75

Years of 1 Amortization 2
3 4 5 6 7 8 9 10 11 12 13 14 15 17 20 25 30

90.14 48.37 34.54 27.70 23.66 21.01 19.16 17.80 16.78 15.98 15.35 14.85 14.44 14.10 13.83 13.40 12.98 12.61 12.44

90.26 48.49 34.67 27.83 23.79 21.15 19.30 17.95 16.92 16.13 15.51 15.01 14.60 14.27 14.00 13.58 13.17 12.81 12.64

90.38 48.61 34.79 27.96 23.92 21.28 19.44 18.09 17.07 16.29 15.67 15.17 14.77 14.44 14.17 13.75 13.35 13.00 12.84

90.49 48.72 34.91 28.08 24.05 21.42 19.58 18.24 17.22 16.44 15.82 15.33 14.93 14.61 14.34 13.93 13.54 13.20 13.05

90.61 48.84 35.03 28.21 24.19 21.55 19.72 18.38 17.37 16.60 15.98 15.49 15.10 14.78 14.51 14.11 13.73 13.39 13.25

90.73 48.96 35.16 28.34 24.32 21.69 19.86 18.53 17.53 16.75 16.14 15.66 15.27 14.95 14.69 14.29 13.91 13.59 13.45

90.85 49.08 35.28 28.47 24.45 21.83 20.00 18.68 17.68 16.91 16.30 15.82 15.43 15.12 14.86 14.47 14.10 13.79 13.65

90.97 49.20 35.40 28.60 24.58 21.97 20.15 18.82 17.83 17.06 16.46 15.99 15.60 15.29 15.04 14.65 14.29 13.98 13.85

91.09 49.32 35.53 28.73 24.72 22.11 20.29 18.97 17.98 17.22 16.63 16.15 15.77 15.46 15.21 14.84 14.48 14.18 14.05

91.20 49.44 35.65 28.86 24.85 22.25 20.44 19.12 18.14 17.38 16.79 16.32 15.94 15.64 15.39 15.02 14.67 14.38 14.26

91.32 49.56 35.78 28.98 24.99 22.39 20.58 19.27 18.29 17.54 16.95 16.49 16.11 15.81 15.57 15.20 14.86 14.58 14.46

91.44 49.68 35.90 29.11 25.12 22.53 20.73 19.42 18.45 17.70 17.11 16.65 16.29 15.99 15.75 15.39 15.05 14.78 14.66

91.56 49.80 36.03 29.24 25.26 22.67 20.87 19.57 18.60 17.86 17.28 16.82 16.46 16.16 15.92 15.57 15.24 14.97 14.8

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139

Appendix 1

Interest Rate 16.50 16.75 17.00 17.25 17.50 17.75 18.00 18.25 18.50 18.75 19.00 19.25 19.50

Years of 1 Amortization 2
3 4 5 6 7 8 9 10 11 12 13 14 15 17 20 25 30

90.97 49.20 35.40 28.60 24.58 21.97 20.15 18.82 17.83 17.06 16.46 15.99 15.60 15.29 15.04 14.65 14.29 13.98 13.85

91.09 49.32 35.53 28.73 24.72 22.11 20.29 18.97 17.98 17.22 16.63 16.15 15.77 15.46 15.21 14.84 14.48 14.18 14.05

91.20 49.44 35.65 28.86 24.85 22.25 20.44 19.12 18.14 17.38 16.79 16.32 15.94 15.64 15.39 15.02 14.67 14.38 14.26

91.32 49.56 35.78 28.98 24.99 22.39 20.58 19.27 18.29 17.54 16.95 16.49 16.11 15.81 15.57 15.20 14.86 14.58 14.46

91.44 49.68 35.90 29.11 25.12 22.53 20.73 19.42 18.45 17.70 17.11 16.65 16.29 15.99 15.75 15.39 15.05 14.78 14.66

91.56 49.80 36.03 29.24 25.26 22.67 20.87 19.57 18.60 17.86 17.28 16.82 16.46 16.16 15.92 15.57 15.24 14.97 14.87

91.68 49.92 36.15 29.37 25.39 22.81 21.02 19.72 18.76 18.02 17.44 16.99 16.63 16.34 16.10 15.76 15.43 15.17 15.07

91.80 50.04 36.28 29.51 25.53 22.95 21.16 19.88 18.91 18.18 17.61 17.16 16.80 16.52 16.28 15.94 15.63 15.37 15.28

91.92 50.17 36.40 29.64 25.67 23.09 21.31 20.03 19.07 18.34 17.78 17.33 16.98 16.69 16.47 16.13 15.82 15.57 15.48

92.04 50.29 36.53 29.77 25.80 23.23 21.46 20.18 19.23 18.50 17.94 17.50 17.15 16.87 16.65 16.32 16.01 15.78 15.68

92.16 50.41 36.66 29.90 25.94 23.38 21.61 20.33 19.39 18.67 18.11 17.67 17.33 17.05 16.83 16.50 16.21 15.98 15.89

92.28 50.53 36.78 30.03 26.08 23.52 21.76 20.49 19.55 18.83 18.28 17.85 17.50 17.23 17.01 16.69 16.40 16.18 16.09

92.40 50.65 36.91 30.16 26.22 23.66 21.91 20.64 19.71 19.00 18.45 18.02 17.68 17.41 17.19 16.88 16.60 16.38 16.30

Interest Rate 19.75 20.00 20.25 20.50 20.75 21.00 21.25 21.50 21.75 22.00 22.25 22.50 22.75

Years of 1 Amortization 2
3 4 5 6 7 8 9 10 11 12 13 14 15 17 20 25 30

92.51 50.77 37.04 30.30 26.35 23.81 22.06 20.80 19.87 19.16 18.62 18.19 17.86 17.59 17.38 17.07 16.79 16.58 16.50

92.63 50.90 37.16 30.43 26.49 23.95 22.21 20.95 20.03 19.33 18.79 18.37 18.04 17.77 17.56 17.26 16.99 16.78 16.71

92.75 51.02 37.29 30.56 26.63 24.10 22.36 21.11 20.19 19.49 18.96 18.54 18.21 17.95 17.75 17.45 17.18 16.99 16.92

92.87 51.14 37.42 30.70 26.77 24.24 22.51 21.27 20.35 19.66 19.13 18.72 18.39 18.14 17.93 17.64 17.38 17.19 17.12

92.99 51.26 37.55 30.83 26.91 24.39 22.66 21.42 20.51 19.83 19.30 18.89 18.57 18.32 18.12 17.83 17.58 17.39 17.33

93.11 51.39 37.68 30.97 27.05 24.54 22.81 21.58 20.67 19.99 19.47 19.07 18.75 18.50 18.31 18.02 17.78 17.60 17.53

93.23 51.51 37.80 31.10 27.19 24.68 22.96 21.74 20.84 20.16 19.64 19.24 18.93 18.69 18.49 18.22 17.97 17.80 17.74

93.35 51.63 37.93 31.24 27.34 24.83 23.12 21.90 21.00 20.33 19.82 19.42 19.11 18.87 18.68 18.41 18.17 18.00 17.95

93.47 51.75 38.06 31.37 27.48 24.98 23.27 22.06 21.17 20.50 19.99 19.60 19.30 19.06 18.87 18.60 18.37 18.21 18.15

93.59 51.88 38.19 31.51 27.62 25.13 23.43 22.22 21.33 20.67 20.17 19.78 19.48 19.24 19.06 18.80 18.57 18.41 18.36

93.71 52.00 38.32 31.64 27.76 25.27 23.58 22.38 21.50 20.84 20.34 19.96 19.66 19.43 19.25 18.99 18.77 18.62 18.57

93.84 52.13 38.45 31.78 27.90 25.42 23.74 22.54 21.66 21.01 20.52 20.14 19.84 19.62 19.44 19.18 18.97 18.82 18.77

93.96 52.25 38.58 31.91 28.05 25.57 23.89 22.70 21.83 21.18 20.69 20.32 20.03 19.80 19.63 19.38 19.17 19.03 18.98

140

Builders Guide to Energy Efficient Homes in Georgia

Appendix 2 .ingertip .acts

Appendix 2

Builders Guide to Energy Efficient Homes in Georgia

141

Appendix 2

This section contains statistical energy information-- conversion factors, R-values, fuel prices, energy efficiency recommendations, and climatic data for Georgia. It serves as a reference guide for those seeking a quick answer to an energy question.

Abbreviations

Btu
one heit when a 1 F MMBtu kWh kW cf cfm bbl gal

British Thermal Unit, the amount of heat needed to increase the temperature of
pound of water one degree Fahren(about the amount of heat released kitchen match burns) one degree Fahrenheit million Btu kilowatt-hour kilowatt cubic foot cubic foot per minute barrel gallon

1 gallon fuel oil = 136,000 Btu 1 gallon propane = 91,500 Btu 1 ton bituminous (Eastern) coal = 2126 MMBtu 1 ton sub-bituminous (Western) coal = 1418 MMBtu 1 cord wood = 128 cubic feet (4 ft x 4 ft x 8 ft ) 1 cord dried oak = 23.9 MMBtu 1 cord dried pine = 14.2 MMBtu

Average Daily Solar Radiation
(Btu/sq ft on a Vertical Surface)

Month January July

Atlanta 884 821

Savannah 962 803

Macon 940 807

Heating Degree Days and Cooling Hours

Energy and .uel Data
Energy Units
1 kWh = 3,412 Btu 1 MMBtu = 293 kwh 1 Btu = 252 calories 1 Btu = 1,055 joules

Heating Degree Days ( HDD ) are a measure of how cold a location is in winter.
Cooling Degree Days (CDD) are a measure of how hot a climate is in summer.
Equivalent Full Load Compressor Hours (EFLCH) show the average number of hours an air conditioner operates.

Power Units
1 watt = 3.412 Btu/hour 1 kW = 3,412 Btu/hour 1 horsepower = 746 watts 1 ton of cooling = 12,000 Btu/hour
.uel Units
1 cf of natural gas ~ 1,000 Btu 1 therm = 100,000 Btu 1 bbl fuel oil = 42 gallons 1 bbl fuel oil = 5.8 MMBtu 1 ton fuel oil = 6.8 bbl

Location Atlanta

HDD 3,095

Savannah 1,952

Macon

2,240

Augusta

2,547

CDD 1,589 2,354 2,217 1,935

EFLCH 1,170 1,460 1,410 1,360

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Appendix 2

HVAC Equipment Efficiencies
Annual Fuel Utilization Efficiency (AFUE) shows the average annual efficiency at which fuelburning furnaces operate.
Coefficient of Performance (COP) measures how many units of heating or cooling are delivered for every unit of electricity used in a heat pump or air conditioner.
Heating Season Performance Factor (HSPF) measures the average number of Btu of heating delivered for every watt-hour of electricity used by a heat pump.
Seasonal Energy Efficiency Ratio (SEER) measures how readily air conditioners convert electricity into cooling--a SEER of 10 means the unit provides 10 Btu's of cooling per watt-hour of electricity.
Insulating Values
The R-value is the measure of resistance to heat flow via conduction. R-values vary according to specific materials and installation.

Building Materials

R-value per inch

Drywall

.9

Wood siding

.9 to 1.2

Common brick

.2

Lumber and siding

Hardwood

.8 to .94

Softwood

.9 to 1.5

Plywood

1.3

Particle Board (medium density) 1.1

Asbestos-cement (entire shingle) .21

Building Materials

Total R-value

Concrete block (entire block)

Unfilled

2

Filled with vermiculite/perlite 4-6

Filled with cement mortar

1.8

Dead Air Spaces

R-value of air space

1/2-inch

.75

3/4-inch

.77

31/2-inch

.80

31/2-inch, reflecting surface on one side 1.6

31/2-inch, reflecting surface both sides 2.2

Insulation
Fiberglass batts/rolls Fiberglass loose-fill Rockwool loose-fill Cellulose Vermiculite Perlite

R-value per inch
3.2 2.2 2.6 3.7 2.1 3.3

Rigid Insulation Boards

R-value per inch

Fiberboard sheathing

2.6

(noninsulating blackboard)

Expanded polystyrene

4.0

(beadboard)

Extruded polystyrene

5.0

Polyisocyanurate and polyurethane 7.2

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Appendix 2
Notes:

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Builders Guide to Energy Efficient Homes in Georgia

Appendix 3
Appendix 3 Earth Craft HouseSM Sensibly Built for the Environment

Builders Guide to Energy Efficient Homes in Georgia

145

Appendix 3

Earth Craft HouseSM Sensibly Built for the Environment
Earth Craft HouseSM is a new builder training and certification program to encourage environmentally friendly building practices. Earth Craft HouseSM provides a blueprint for builders that want to build healthy, comfortable, affordable homes that reduce energy and water bills and protect the environment.
The program awards points for a broad variety of environmentally-sensitive practices in site development, design, construction, consumer education, and marketing areas. Developed by the Greater Atlanta Home Builders Association, the largest home builder group in the country, in conjunction with the National Association of Home Builders Research Center and Southface Energy Institute, Earth Craft HouseSM serves as a pilot for home building associations across the country. Additional sponsors include Georgia Environmental Facilities Authority, Georgia Pacific, Home Depot, and Andersen Windows. A renovation program is planned for the future.
Below is a worksheet of actions (version from October 11, 1999; points will change over time) that builders can employ on individual homes to acquire Earth Craft HouseSM designation. Look to these actions to identify and implement environmentallysensitive building practices. For more information contact:
Greater Atlanta Home Builders Association 1399 Mortreal Rd. Tucker, GA 30084 770-938-9900 www.atlantahomebuilders.com

SITE PLANNING

erosion control site plan

8

workshop on erosion and sediment control

2

topsoil preservation

5

grind stumps and limbs for mulch

3

mill cleared logs

2

BUILDING WITH TREES (NAHB PROGRAM) 25

builder may choose to certify house meets Building With Trees program OR earn points from individual tree protection and planting measures

TREE PROTECTION AND PLANTING MEASURES

tree preservation plan

5

no trenching through tree root zone (per tree)

1

no soil compaction of tree root zone

2

tree planting

4

wildlife habitat

2

ENERGY EFFICIENT BUILDING ENVELOPE AND SYSTEMS

ENERGY STAR

90

builder may choose to certify house meets ENERGY STAR OR earn a minimum of 75 points from Energy Measures

ENERGY MEASURES
(must earn a minimum of 75 points, Energy Measure points cannot exceed 85 points)Houses must meet or exceed the Georgia Energy Code

AIR LEAKAGE TEST Builder must provide documented
proof of certified test to homeowner

Certify maximum 0.35 air changes per hour

35

OR earn points for individual air sealing measures

AIR SEALING MEASURES

bottom plate of exterior walls

2

floor penetrations between unconditioned

and conditioned space

2

bath tub and shower drain

2

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Appendix 3

cantilevered floors sealed above supporting wall

2

drywall sealed to bottom plate of exterior walls

2

fireplace air sealing package (all units)

2

drywall penetrations in exterior walls

2

exterior wall sheathing sealed at plates,

seams, and openings

5

housewrap (unsealed at seams and openings)

2

housewrap (sealed at plates, seams, and openings)

8

window rough openings

2

door rough openings

1

airtight IC recessed lights or no recessed

lights in insulated ceilings

4

attic access opening

(pulldown stairs/scuttle hole)

2

attic kneewall doors (weatherstripped with latch)

2

attic kneewall has sealed exterior sheathing

5

chases sealed and insulated

5

ceiling penetrations sealed between

unconditioned and conditioned space

2

ceiling drywall sealed to top plate

2

band joist between conditioned floors sealed

3

INSULATION *Homes with multiple foundation types must
use foundation type of greatest area for points

*slab insulation

2

*basement walls (continuous floor to ceiling R10)

3

*framed floor over unconditioned space (R19)

1

*sealed, insulated crawl space walls (R10)

1

*cantilevered floor (R30)

2

insulate fireplace chase

1

spray applied wall insulation

4

exterior wall stud cavities (R15)

1

insulated headers

2

insulated corners

2

insulated T-walls (exterior/interior wall intersection)

2

insulated wall sheathing (R 2.5 or greater)

2

insulated wall sheathing (R 5 or greater)

3

band joist insulated (R19)

2

loose-fill attic insulation card and rulers

1

energy heel trusses or raised top plate

2

flat ceilings (R30)

1

flat ceilings (R38)

2

vaulted and tray ceilings (R25)

1

vaulted and tray ceilings (R30)

2

ceiling radiant heat barrier

1

attic kneewall stud cavities (R19)

3

attic kneewall with insulated sheathing (R5)

5

attic kneewall doors (R19)

2

attic access doors (R19)

2

WINDOWS

NFRC rated windows ( max U.56)

3

low emissivity glazing

5

gas-filled double glazed units

3

solar heat gain coefficient (max 0.4)

3

1.5-foot overhangs on all sides

1

solar shade screens

3

west facing glazing less than 2% of floor area

2

east facing glazing less than 3% of floor area

2

certified passive solar design (25% load reduction)

10

HEATING AND COOLING EQUIPMENT *Builder must
provide documented proof of certification to homeowner

*cooling equipment sized within 10%

of Manual J (all units)

5

*heating equipment sized within 10%

of Manual J (all units)

5

*measured airflow within 10% of

manufacturer's specifications

3

90% AFUE furnace (per unit)

3

SEER 12 cooling equipment (per unit)

2

SEER 14 cooling equipment (per unit)

3

HSPF 7.8 heat pump

2

HSPF 8.0 heat pump

3

Builders Guide to Energy Efficient Homes in Georgia

147

Appendix 3

geothermal heat pump

4

*sensible heat fraction (max 0.7, all units)

2

programmable thermostat

1

outdoor thermostat for heat pump

1

*cooling equipment has

non CFC or HCFC refrigerant

3

zone control--one system services multiple zones

5

DUCTWORK/AIR HANDLER *Builder must provide
documented proof of certification to homeowner

*certify duct leakage less than 5%

20

air handler located within

conditioned space (all units)

5

ducts located within

conditioned space (min 90%)

5

duct seams and air handler sealed with mastic

10

*duct design complies with Manual D

5

*airflow for each duct run

measured and balanced

3

no ducts in exterior walls

3

longitudinal supply trunk

1

multiple return ducts

2

interior doors with 1-inch clearance

to finish floor

2

R8 duct trunk lines that are

outside conditioned space insulated to R8

2

ENERGY EFFICIENT LIGHTING/APPLIANCES

indoor fluorescent fixtures

2

recessed light fixtures are compact fluorescents

2

outdoor lighting controls

2

high efficiency exterior lighting

2

energy efficient dishwasher

1

energy efficient refrigerator

2

no garbage disposal

1

RESOURCE EFFICIENT DESIGN

floor plan adheres to 2-ft dimensions

2

interior living spaces adhere to 2-ft dimensions

1

floor joists @ 24-in. centers (per floor)

3

floor joists @ 19.2-in. centers (per floor)

2

non-load bearing wall studs @ 24-in. centers

2

all wall studs @ 24-in. centers

3

window rough openings eliminate jack stud

2

non-structural headers in non-load bearing walls

2

single top plate with stacked framing

3

2-stud corners with drywall clips

or alternative framing

3

T-walls with drywall clips or alternative framing

3

RESOURCE EFFICIENT BUILDING MATERIALS

RECYCLED/ NATURAL CONTENT MATERIALS

concrete with fly ash

3

insulation

1

flooring

1

carpet

1

carpet pad

1

carpet label

1

outdoor decking and porches

2

air conditioner condensing unit pad

1

ADVANCED PRODUCTS

engineered floor framing

2

engineered roof framing

2

OSB roof decking

1

OSB floor decking

1

non-solid sawn wood or steel beams

1

non-solid sawn wood or steel headers

1

engineered wall framing

1

engineered interior trim

1

engineered exterior trim including cornice

1

steel interior walls

1

Structural Insulated Panels (exterior walls)

5

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Appendix 3

Structural Insulated Panels (roof)

3

Precast Autoclaved Aerated Concrete

5

Insulated Concrete Forms

5

DURABILITY

roofing (min. 25-year warranty)

1

roofing (min. 30-year warranty)

2

roofing (min. 40-year warranty)

3

subfloor decking (min. 40-year warranty)

1

light roof color (asphalt or fiberglass shingles)

1

light roof color (tile or metal)

2

roof drip edge

1

exterior cladding (min. 3 sides with 40-year warranty or

masonry)

1

walls covered with builder paper or housewrap (drainage

plane)

1

siding with vented rain screen

1

back-primed siding and trim

1

insulated glazing (min. 10-year warranty)

1

window and door head flashing

1

continuous foundation termite shield

1

roof gutters that direct water away from foundation

1

covered entry way

1

WASTE MANAGEMENT

WASTE MANAGEMENT PRACTICES *Builder must
provide documentation (receipt) of donated materials

job site framing plan and cut list

10

central cut area

3

*donation of excess materials

or re-use (min. $500/job)

1

RECYCLE CONSTRUCTION WASTE

posted job site waste management plan and

recycle 75% of each material

5

wood

3

cardboard

1

metal

1

drywall (recycle or grind and spread on site)

3

plastics

1

shingles

1

INDOOR AIR QUALITY

COMBUSTION SAFETY

detached garage

5

attached garage--seal bottom plate and

penetrations to conditioned space

4

attached garage--exhaust fan controlled

by motion sensor or timer

2

direct vent, sealed combustion fireplace

3

furnace combustion closet isolated from conditioned area 4

water heater combustion closet isolated or power vented 4

carbon monoxide detector

4

house depressurization test

6

MOISTURE CONTROL

drainage tile on top of footing

1

drainage tile at outside perimeter edge of footing

2

drainage board for below grade walls

4

gravel bed beneath slab-on-grade floors

3

vapor barrier beneath slab (above gravel) and in crawl space 2

capillary break between foundation and framing

1

VENTILATION

radon/soil gas vent system

3

radon test of home prior to occupancy

2

high efficiency, low noise bath fans

3

tub/shower room fan controls

1

kitchen range hood vented to exterior

3

ceiling fans (minimum 3 fans)

1

whole house fan

2

controlled house ventilation (.35 ACH)

4

dehumidification system

3

vented garage storage room

1

no power roof vents

1

Builders Guide to Energy Efficient Homes in Georgia

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Appendix 3

dampered fresh air intake

2

MATERIALS

no urea formaldehyde materials inside conditioned space 2

urea formaldehyde materials inside

conditioned space sealed

1

low VOC paints, stains, finishes

1

low VOC sealants and adhesives

1

low VOC carpet

1

alternative termite treatment

2

central vacuum system

1

filter/air cleaner with minimum 30% dust spot efficiency 2

protect ducts during construction

2

WATER--INDOOR

water filter (NSF certified)

1

high efficiency clothes washer

2

pressure reducing valve

1

high efficiency plumbing fixtures

2

hot water demand re-circulation

1

shower drain heat recovery device

1

water heater (Energy Star: gas .62, electric .92)

2

water heater tank insulation

1

pipe insulation

1

heat traps

1

heat recovery water heating

1

solar domestic water heating

3

heat pump water heater

2

WATER--OUTDOORS

HBA WATER SMART program

5

xeriscape plan

5

xeriscape installed

15

timer on hose bibs or irrigation system

1

efficient irrigation system

(min. 50% plantings with drip system)

2

greywater irrigation

3

rainwater harvest system

3

permeable pavement driveway/parking area

1

HOMEBUYER EDUCATION/OPPORTUNITIES

guaranteed energy bills

15

review energy operations manuals with homeowner

4

review irrigation system operations

manuals with homeowner

2

built-in recycling center

2

local recycling contact

1

household hazardous waste resources

1

environmental features checklist for walk-through

1

BUILDER OPERATIONS

builds 10% of total houses to

Earth Craft HousesSM standards

3

OR builds 80% of total houses to

Earth Craft HousesSM standards

5

markets Earth Craft HouseSM program

2

environmental checklist provided to all subcontractors

1

Certified Professional Home Builder

3

uses HBA Homeowner Handbook for warranty standards 2

BONUS POINTS

site located within .25 mile of mass transit

5

sidewalk connects house to business district

5

brownfield site

5

solar electric system

25

Alternative vehicles: electric charging station

or natural gas pump

5

American Lung Association Health House

5

exceeds Energy Star (1 point for each 1%) for a max. of 5

Innovation Points -- Builder submits specifications for innovative products or design features to qualify for additional points

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Appendix 4 Resources

Appendix 4

Builders Guide to Energy Efficient Homes in Georgia

151

Appendix 4

Resources
Sustainable Building
s American Council for an Energy Efficient Economy (ACE3) 1001 Connecticut Avenue, NW, Suite 801 Washington, DC 20036 Research and Conferences: 202-429-8873 Publications: 202-429-0063 www.aceee.org
s Center for Resourceful Building Technology P.O. Box 100 Missoula, MT 59806 406-549-7678 www.montana.com/CRBT
s Efficient Windows Collaborative Alliance to Save Energy 1200 18th Street N.W., Suite 900 Washington, DC 20036 202-857-0666 www.efficientwindows.org/
s Energy Design Update Cutter Information Corp. 37 Broadway, Suite 1 Arlington, MA 02174-5539 800-964-5125 www.cutter.com
s Energy Efficient Building Association (EEBA) 490 Concordia Avenue St. Paul, MN 55103-2441 651-268-7585 www.eeba.org
s Energy Efficient Lighting Association P.O. Box 727 Princeton Junction, NJ 08550 609-799-4900 www.eela.com
s ENERGY STAR Program U.S. Environmental Protection Agency Atmospheric Pollution Program Division 401 M St, SW (6202J) Washington, DC 20460 202-564-9190 or 888-STAR-YES www.epa.gov/homes (residential) www.epa.gov/buildings (commercial)

s Environmental Building News E Build, Inc. 122 Birge St., Suite 30 Brattleboro, VT 05301 802-257-7300 www.ebuild.com
s Georgia Department of Natural Resources Pollution Prevention Assistance Division (construction waste management) 7 Martin Luther King Jr. Drive, Suite 450 Atlanta, GA 30334-9004 404-651-5120 www.ganet.org/dnr/p2ad/
s Georgia Environmental Facilities Authority (GEFA) Division of Energy Resources 100 Peachtree Street, Suite 2090 Atlanta, GA 30303 404-656-5176 www.gefa.org
s Home Energy Energy Auditor and Retrofitter, Inc. 2124 Kittredge Street #95 Berkley, CA 94704 510-524-5405 www.homeenergy.org
s Journal of Light Construction Builderburg Partners, Ltd. 932 West Main St. Richmond, VT 05477 802-434-4747 www.jlconline.com
s Lighting Research Center Rensselaer Polytechnic Institute 110 8th Street Watervliet Facility Troy, NY 12180 518-276-8716
s National Association of Home Builders Research Center 400 Prince George's Boulevard Upper Marlboro, MD 20774 301-249-4000 www.nahbrc.com
s National Fenestration Rating Council (NFRC) 1300 Spring St., Suite 500 Silver Spring, MD 20910 301-589-NFRC www.nfrc.org

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s Oak Ridge National Laboratory Buildings Technology Center, Building Envelope Research P. O. Box 2008, MS 6070 Oak Ridge, TN 37831-6070 423-574-0022 www.ornl.gov/roofs+walls/
s Southface Energy Institute, Inc. 241 Pine Street Atlanta, GA 30308 404-872-3549 www.southface.org
s Sustainable Building Industry Council (formerly Passive Solar Industries Council) 1331 H Street, Suite 1000 Washington, DC 20005 202-628-7400 www.sbicouncil.org
s U.S. Department of Energy Energy Efficiency and Renewable Energy Clearinghouse (EREC) P.O. Box 3048 Merrifield, VA 22116 800-363-3732 www.eren.doe.gov
s U.S. Department of Energy Office of Codes and Standards (energy efficient appliances) www.eren.doe.gov/buildings/ consumer_information/index.html
Energy Codes
s Georgia Energy Code Georgia Department of Community Affairs Planning & Codes 60 Executive Park South, NE Atlanta, GA 30329 404-679-4940 www.dca.state.ga.us/planning/codespdf/ codesintro.html
s U.S. DOE Building Standards & Guidelines Program (BSGP) 1-800-270-CODE (2633) www.energycodes.org

Home Energy Rating Systems (HERS) and Energy Efficient Mortgages
In April 1995, the National Association of State Energy Officials and Energy Rated Homes of America founded the Residential Energy Services Network (RESNET) to develop a national market for home energy rating systems and energy efficient mortgages. RESNET's activities are guided by a mortgage industry steering committee composed of the leading national mortgage executives.
Go to www.natresnet.org to view information on:
s Home energy ratings www.natresnet.org/herseems/default.htm
s Energy efficient mortages www.natresnet.org/herseems/default.htm
s List of Georgia certified home energy raters www.natresnet.org/dir/raters/Georgia.htm
s List of Georgia financing programs www.natresnet.org/dir/lenders/ Georgia.htm
Radon
s General Radon Hotline Anywhere in Georgia call: 1-800-745-0037 Atlanta residents call: 404-872-3549 ext. 0
s U.S. EPA National Safety Council (call for test kits and general information) 1-800-767-7236
s NEHA-certified Radon Testers and Mitigators 1-800-269-4174 www.radongas.org

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Appendix 4
Notes:

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Builders Guide to Energy Efficient Homes in Georgia