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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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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.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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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