Putting the sun to work : a guide to residential solar energy options in Georgia

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A Guide to Residential Solar Energy Options in Georgia
Volume 1: Introduction

PUTTING THE SUN TO WORK)
A Guide to Residential Solar Energy Options in Georgia ,
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Volume 1: Introduction
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Georgia. Office of Energy Resources
Prepared by: Georgia Solar Coalition, Inc.
August, 1981

For additional copies of this document or other information, please contact: Georgia Office of Energy Resources Room 615 270 Washington Street, SW Atlanta, GA 30334 (404) 656-5176
This document was prepared under contract to the Georgia Office of Energy Resources by the Georgia Solar Coalition (GSC). The GSC may be reached at:
Georgia Solar Coalition 1103 Euclid Avenue, NE
P. o. Box 5506
Atlanta, GA 30307 (404) 525-7657
This booklet is one of a three-volume series: Volume 1: Introduction Volume 2: Solar Energy in Existing Buildings Volume 3: Solar Energy in New Construction

Credits

Drawings:

Tammy Chambless and the National Conservation and Renewable Energy Inquiry and Referral Service.

Layout:

Printed Matter

Word Processing: Verna Hankins

Table of Contents

Title

Page

Introduction

1

Renewable Energy Designs for Georgia's Homes . . .

2

Direct Use of the Sun

. 2

Basic Solar Concepts

. . .2

Solar Water Heating .

. 4

Passive Space Heating . . . .

6

Active Space Heating

12

Solar Cooling and Earth Tempering

. . . . . . . . . 14

Combined Systems

20

Direct Solar: References

22

Wood Stoves and Fireplaces

. 23

Electricity from Renewable Resources

. 24

Photovoltaic Solar Cells Solar Thermal Systems Solar Ponds . . . . Water and Wind Energy Electricity from Renewable Resources:

References.

. . 24 25 25
26 26

The Home Solar Survey

. 27

Step 1: Check for Energy Conserving Features Step 2: Determine Orientation . . . Step 3: Assemble Solar Site Analyzer . . Step 4: Draw Floor Plans and Check for Shading Step 5: Select Solar Designs Sample Solar Survey . . . How Much Will Solar Cost?

. 27 28
28 . 29 . 30 31
32

Where Should You Go From Here?

33

How to Select a Solar Professional What if the Sun Stops Shining? What to Put in a Solar Contract Summary . . . . . Energy Information Resources

. 33
34 34
. . . . . . 35 . 36

Glossary

37

Introduction
Every year, Georgians use 250 trillion BTU's of energy in their homes. That is the equivalent of almost 2 billion gallons of gasoline, or enough to drive around the earth 1.5 million times.
The energy sources on which we currently rely are fossil fuels, such as natural gas, petroleum and coal. Our national and global reserves of these fuels are being depleted at an ever-increasing rate. Since our fuel resources are growing more precious and, consequently, more expensive, all of us are gravely concerned about the vast quantities of energy we use. Adding to this concern is the fact that Georgians must import over 97% of our energy since we have very few fossil fuel resources.
Georgia, however, is extremely rich in renewable resources such as solar energy and wood energy. Georgia receives 2500 hours of sunlight per year on the average; and our state has the second highest wood resource base in the country. Unlike fossil fuels, the sun's energy is inexhaustible; and with wise use, our forests replenish themselves quickly. This booklet will discuss how we can put these renewable resources to work in our own homes.
The chart to the right shows how a typical Georgia home uses energy. Note that over two-thirds of the energy requirements are for space heating, water heating, and space cooling. These uses all involve thermal energy -- heat -- in a direct way. Space heating and water heating supply thermal energy to a house, while space cooling removes it. Solar energy, wood energy, and energy conserving designs can easily supply these thermal energy needs. Thus, the technologies and designs discussed in this booklet have a high potential for supplanting most of the fuel we currently use in our homes.
1

Renewable Energy Designs for Georgia's Homes

Direct Use of the Sun
The renewable energy designs with which most of us are familiar use direct sunlight. Incoming solar energy is captured and used to heat living areas or water for domestic purposes. Designs that use direct sunlight to provide energy for a home can be divided into two categories: passive solar and active solar.
Passive solar systems, as the name implies, require no outside energy to function. They rely on natural forces to control heat flows within a building. In fact, the building itself becomes the collector of the sun's energy.
Active systems, on the other hand, use pumps or blowers that require electricity to transfer fluids between components of the system. Active systems typically use solar collector panels to capture the heat of the sun. The panels, located on the roof or ground, transport a heated fluid to storage vessels.
Basic Solar Concepts
All solar energy designs rely on a few basic concepts. The size, appearance and performance differ dramatically, but all designs intended to capture the sun's rays have similar features. The drawing below shows a generic solar design possessing components common to the options discussed in this booklet.

Glazing
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Storage

Living Area

Absorber

Heat Distribution

In the generic design, sunlight first travels through one or two outer layers of glazing. This outer skin of the design can be made of glass, fiberglass of any material through which sunlight can pass freely. After traveling through the glazing, the light energy strikes a dark surface into which it is absorbed. The absorber, whose outer surface is dark, converts the incoming light energy to heat energy. In so doing, its temperature increases dramatically. The heat accumulating within the absorber is transferred to a storage chamber.

Thermal or heat storage is the key to a solar design's success. With thermal

storage, a solar house can stay warm at night or over several cloudy days. Storage

tanks holding solar-heated water for domestic purposes will remain warm on days

having little sun. Common storage materials are basic-- water, brick, concrete and

rock.

2

Once the solar-derived heat is stored, find a way to transfer it to the living space or to your water supply, depending on whether you want space heating or water heating. A number of mechanisms, including conduction, convection and radiation, exist for heat distribution in solar energy designs.
Conduction is simply the movement of heat through a surface. When you burn yourself by touching the handle of a frying pan, the villain is conduction. Heat moved from the burner to the bottom of a pan, up the sides and through the handle to your now-swollen fingers.
Convection is the circulation caused when air heats unevenly. As air increases in temperature, its density decreases -- it becomes lighter. Gravity causes this lighter air to flow upward. In a room, as the rising, heated air comes in contact with a ceiling that has a cold attic just above, its temperature declines. When it cools, it becomes more dense, and gravity pushes it down to the floor again. The rising and consequent sinking of air creates a flow within a room or house that is called either a convective loop or a thermo syphoning loop. Heat or thermal energy is the driving force that causes thermosyphoning to occur.
Radiation, the third mode of heat transfer, is the tendency of warm objects to heat up nearby cool objects by emitting long wave thermal energy. An example of an excellent supplier of radiant heat is a campfire. While sitting in front of a fire, you will remain warm even though the outside air temperature may be quite cold. Of course, only half of you heats up at one time, so on a particularly cold night, you often have to turn around to warm up your backside:
Radiation works in our favor in solar energy systems. In our general design, sunlight, which moves in very short waves, traveled through the glazing and struck the absorber. As it was absorbed, it changed from light energy to heat energy, thus increasing the absorber's temperature. Radiant heat energy travels in long waves. While the glazing allowed the light energy in, it does not allow the longer-wave, heat energy to escape. The process of trapping the heat energy is called the greenhouse effect. A common example is a car that heats up on a winter day with its windows closed. The greenhouse effect is the basis for practically all solar designs.
The way in which the different mechanisms of heat distribution combine is a critical part of the overall solar design. In homes with inadequate facilities for transporting heat, rooms tend to overheat, and the solar investment is slow to pay off.
The design of the elements of the solar energy system is critical. A noted solar expert says, "Solar is simple, but fragile." The financial and aesthetic benefits of solar are substantial, but you must be careful with the design.

Solar Water Heating Since you use hot water year-round and only use space heating or cooling seasonally, it is a good idea to consider solar water heating for your first solar home improvement
There are three main types of solar water heaters -- batch-type, or breadbox heaters, thermosyphoning water heaters, and active water heaters. Batch and thermosyphon water heaters are passive systems, but all solar water heaters use the same basic concepts discussed in the preceding section.
The simplest solar water heater is the batch heater. In this design, water storage tanks, which sit in an insulated box, also act as the absorber. The box, whose top is covered with glazing, has hinged, insulated shutters that close at night and on extremely cloudy days. The shutters keep the heat that is collected during the day sealed inside the box and storage tanks.
Batch heaters are the least expensive of the solar water heating options; however, they are bulky, somewhat unattractive and have the lowest performance of the available designs. They also require daily owner intervention -- someone must open and close the shutters.
Batch heaters can be mounted on the ground, on a structurally sound roof, or as part of the house itself. The tanks can lie horizontally, although vertical placement improves performance. As you consider the options, keep in mind that a batch heater in normal operation weighs over 600 pounds.
Ranch House with Batch Water Heater
Colonial House with Batch Water Heater
Unlike the batch heater, the thermosyphon and active designs use solar collecting panels to heat water using the sun's energy. Solar panels are thin boxes typically three feet wide and six feet long. They contain two layers of glazing and a black absorber plate which possesses numerous tubes. The tubes hold a fluid --usually water -- which moves through the absorber plate and heats up during a sunny day. The solar-heated fluid then travels to a well-insulated water storage tank where it transfers its heat to water stored for household use. The fluid travels back to the solar collectors for reheating.
4

In general, the thermosyphon and active systems are identical except that active systems require pumps, temperature sensors, and control systems. An active water heater has more flexibility because the collectors may be located in any sunny spot, and the tank placed wherever there is room. The active system is also more efficient than the breadbox. The most efficient system, however, is the thermosyphon, in which fluid is pumped by the power of convection. If the storage tank is elevated hig~er than the collectors, the fluid heated in the collectors will rise toward the tank w ile cooler, heavier fluid at the bottom of the tank will sink to the collectors to be reheated and rise again. This process is automatic, fail safe, consumes no external energy, and is dependent only on the proper placement of collectors and tank. Thermosyphon systems have been in use since 1909; over 400 units in Albany, Georgia, have been operating continuously for 30 years.
To decide between an active and a thermosyphon system, you must determine whether you can feasibly locate a storage tank above your solar collectors. This may involve locating your collectors at the lowest edge of the roof to allow space above (in the attic) for your tank, or it may require mounting your collectors on the ground, in which case additional problems of shading and hazards of and to children must be solved.
Any solar energy design in which exterior water piping occurs must consider the problem of freeze protection. Many solar water heaters have failed because they have frozen. A pipe that bursts can cause damage to more than the solar components themselves. Be certain to ascertain what the risks of freezing are for the solar water heaters you are considering. Most companies that have been in the solar business for a few years install reliable systems that they guarantee. For more information on how to identify a solar contractor, see the last section of this booklet.
Active Water Heaters

Thermosyphon Water Heaters 5

SOLAR HEATED WATER

Passive Space Heating
Passive solar designs, unknown until a few years ago, have received a great deal of publicity lately. The attention has been well deserved. Passive features require only minor modifications in the design of a house to achieve considerable energy savings. The house itself becomes the collector, and natural forces control air movement and heat distribution.
In general, passive designs feature broad expanses of glazing on the southfacing walls of a house. The glazing is situated to receive massive doses of sunlight on winter days. Sunlight travels through the glazing and strikes the thermal mass, which is simply a dark-colored wall or floor. Thermal mass doubles as both an absorber of solar energy and a storage mass. Typical types of thermal mass surfaces include ceramic tile imbedded in a concrete floor, brick walls, walls with stucco finishes and water-filled containers.
The process these mass surfaces use at night is radiation. Like a campfire, the warm walls and floors radiate heat to keep you comfortable. Their warm temperature is important because, as the chart below shows, you will feel as comfortable in a room with 560 air temperature and 800 floors and walls as in a room in which both the air and the interior surfaces are at 700. Of course, if the floors and walls were cold, say at 600, you would have to have air temperatures of 840 to be as comfortable.
Conditions of Equal Comfort as a Flmction of Air Temperature and Floor and Wall Temperature
Air Temperature 49 56 63 70 77 84 91
Floor and Wall 85 80 75 70 65 60 55 Temperature
A well-designed passive system will heat up the walls and floors and therefore enable you to feel more comfortable at lower indoor air temperatures.
Many people have the impression that homes using passive designs must have a modern or contemporary style. Although a number of passive homes do have more modern lines, any type of house can use passive solar. This booklet examines the options available for two types of conventional homes: the ranch-style and the colonial. The designs for the non-solar versions of these two homes are shown below and on the next page. The modifications shown in this booklet will give you a sense of the wealth of solar options available.
Floor Plan of Ranch House 6

Floor Plan of Colonial House
Direct Gain
Direct gain designs are simply south-facing windows that allow sunlight to enter a building during winter days. The thermal mass must be incorporated within the interior of the building. Thus, floors in front of the direct gain windows should be tile over concrete or some other design that includes thermal mass. All interior, nonmass surfaces should use light colors.
Direct gain designs have several advantages and disadvantages in relation to other passive solar options:
Advantages
1. They are the least expensive option for a new home. 2 They allow nice views, give a home a warm, open appearance, and
provide lots of natural lighting during the day. 3. They are not unusual looking when compared to today's conventional
homes.
Disadvantages
1. Since the direct gain room is, in essence, a solar collector, daily temperature fluctuations are difficult to control in winter.
2. Colorful fabrics in the direct gain areas may fade. 3. A direct gain space may not offer as much privacy as desired. 4. The storage mass must be located in the direct gain room. Thus,
some floor or wall space must have exposed masonry, or water containers must be used.
7

5. To obtain most of your heating needs from a direct gain system, you must use nighttime insulating shutters over the direct gain windows.
6. Direct gain designs are difficult to install in retrofit situations. Some examples of how direct gain designs can be incorporated into conventional homes are shown below.

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Ranch House with Direct Gain Windows

Colonial House with Direct Gain Windows
Sunspaces
Sunspaces, also known as solar greenhouses, are one of the most popular designs for solar retrofit. Many people have taken screen porches or carports, glazed the south wall, and insulated the other walls to create spaces which are isolated from the rest of the house and can collect and store solar-derived heat. In other homes, the owners have installed sunspaces as entire new rooms located on the south side of their houses.
As in direct gain applications, sunspaces must have adequate storage. Because sunspaces are separated from the rest of the house, owners are more willing to use water-filled containers, which they may reject as a storage option in the living space itself. Some means of transferring heated air to the rest of the house, such as vents or operable windows, must be incorporated into the design. For proper heat distributic;m, the. openings for air movement must occur at both the top and bottom of the common walls between the sunspace and the living space to be heated.
Advantages and disadvantages of sunspaces are as follows:
Advantages
1. Sunspaces provide an environment for growing plants year-round.
2. Sunspaces absorb the shock of the incoming sunlight and reduce the tendency of the living space to fluctuate in temperature.
3. Sunspaces add value to a house as additional floor area in addition to their value as solar-heating devices.
4. Sunspaces are relatively easy to build on to existing homes.
5. Sunspaces are not unusual in appearance and therefore do not represent a major departure from conventional house design. 8

Disadvantages 1. Sunspaces can be relatively expensive since they are basically
additional floor area. 2. Because sunspaces have to heat themselves, they take some of the
solar heat away from the rest of the house. 3. Sunspaces with plants experience high humidity levels, which can
increase humidity levels inthe house itself. Also, odors originating in the sunspace can be carried into the house.
Ranch House with Attached Sunspaces

Convective Loops

Colonial House with Attached Sunspace

Most passive heating options rely on convective loops for proper distribution of solar-heated air. Several passive designs function solely to create a convective loop and pump heat into the living space during the day. An inexpensive design involves glazing over portions of the house's existing south wall which has been painted a dark color. Vents installed at the top and bottom of the wall send heated air into the house and bring in cooler air from the floor of the house for reheating.
Advantages and disadvantages of convective loop collectors are as follows:

Advantages

1. Convective loop collectors are very inexpensive.
2. Because they are isolated from the house, convective loop collectors do not cause overheating problems in the summer.

Disadvantages

1. Convective loop collectors are unusual in appearance.
2. They possess no facilities for storage, thus, they function primarily to provide heat during the day.

Ranch House with Convective Loop 9

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Colonial House with Convective Loop

Thermal Storage Walls
Thermal storage walls feature two layers of glazing located just in front of a large wall of thermal mass. The wall can be made of masonry material or waterfilled containers. During the day, sunlight passes through the glazing and strikes the darkened wall. The wall absorbs the sunlight as heat and gradually increases in temperature. The heat passes through the wall and radiates warmth into the living space. At night, the heat remains in the wall, which keeps the living space heated by radiation. Performance can be improved by installing vents at the top and bottom. Then, convective loops deliver sorne of the heat into the living space.
Disadvantages and advantages of thermal storage walls are as follows:
Advantages
1. Like sunspaces, passive homes with thermal storage walls have low temperature fluctuations.
2. Thermal storage walls require much less additional floor area than sunspaces.
3. When combined with direct gain, they provide a nice balance between day and night heat delivery to the living area.
Disadvantages
1. Thermal storage walls are one of the most expensive passive options; they are difficult to retrofit in most houses.
2. They are unusual in appearance.
3. Once in place, it is difficult to clean the glazing in front of masonry storage walls. Storage walls using water-filled containers allow for cleaning the interior windows, but many people object to having the containers within the living space of the house. Some new containers are now on the market that are specifically designed for storage in interior spaces.

10

Ranch House with Thermal Storage Wall

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Nighttime Shutters

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Colonial House with Thermal Storage Wall
Nighttime Insulation
The large expanses of glazing featured in passive solar designs suffer substantial heat loss at night. Insulated shutters, shown in the above sketch, can reduce losses and improve performance markedly. Thermal shades that pull down to seal over windows, insulating panels that attach to the glazing with magnets, and hinged, insulated shutters are among the variety of options for cutting nocturnal heat loss through windows. With any passive solar design, you should consider the use of night insulation.

II

Active Space Heating
Unlike passive heating designs, in which the house itself functions as the solar collector, active space heating designs use solar collecting panels, located on the roof or on the ground, to capture the sun's energy. The two major categories of active systems are distinguished by the fluid flowing through the collector. One type uses air, and the other uses water.
Air systems have several advantages over water systems. The collector will not corrode, and the fluid (air) will not freeze. If the collectors leak, the consequences will not be as severe as in liquid systems; in addition, the repair will be less costly.
One other advantage of air systems is the relative simplicity of the absorber. Unlike the piping or tubing required in water systems, an air collector uses a single sheet of metal that has been either painted or coated flat black.
There are several disadvantages of air systems. They require large ducts instead of small diameter pipes, therefore, installation of the system, especially when retrofitting, will be more difficult. Air systems require blowers, which typically use more electricity than the pumps in water systems. Perhaps the m?jor disadvantage is that air systems usually store heat in an insulated bin filled with rocks. In order to have enough storage, the rock bin must be of considerable size -- much larger than the storage tank used in the water system. Thus, both the heat distribution and storage components of water systems are more compact than air systems.
Another advantage of water systems is that most of the active solar businesses sell water systems instead of air systems. Therefore, you are more likely to locate a company that installs and guarantees water systems than one that handles air systems.
Active solar heating has several advantages and disadvantages when compared with passive solar heating. The following chart summarizes some general conclusions about these two different solar approaches:

Cost Comfort Design flexibility

PASSIVE
Passive solar heating costs much less than active in new construction. In retrofits, the cost varies.
Passive solar heating can cause interior temperature fluctuation. Warm walls and floors at night make interiors comfortable at lower air temperatures.
The house itself must be oriented and designed to receive, store and distribute the heat.
12

ACTIVE
In addition to extra capital costs, active system owners must pay monthly bills for electricity to power pumps and blowers.
Active solar heating causes no more interior temperature fluctuation than a conventional furnace.
Active solar heating can be applied regardless of the actual design of the house, if a location for the collectors exists.

Appearance
Retrofit Tax Credit Owner intervention

Passive designs can create attractive, open spaces in a house; some features, such as thermal storage walls and water containers, present an unusual appearance.
Passive solar heating applications that supply over 50% of a house's heat tend to be difficult to install in homes already built.
It is difficult to include the entire cost of a passive solar heating system in your request for a federal energy tax credit.
Passive solar systems require homeowners to occasionally perform such chores as opening or closing vents and shutters, cleaning glazing, etc.

Active systems do not alter the appearance of a house other than locating collectors on the roof or ground.
Active collectors can be installed relatively easily on an existing house.
The full cost of an active heating system, up to $10,000, is eligible for a federal tax credit.
Active solar systems require virtually no owner action, except for periodic cleaning of the collectors' glazing.

13

SOLAR COOLING AND EARTH TEMPERING

Importance of Region and Climate

Passive cooling in the Southeast is faced with numerous climatic difficulties. Seemingly all of the climatic characteristics in the Southeast -- humidity levels, breezes, ambient air temperatures, day-night temperature differential, etc. -- defy the feasibility of total passive cooling. However, numerous avenues exist to work with the climate through building design to reduce dependence on mechanical cooling devices.

Window Selection and Shading

One of the primary factors driving up cooling bills in both solar and non-solar

homes is excessive use of east and west windows. Many people do not realize that in

the sumrner, windows located on the east or west receive two to three times as much

sunlight as south-facing windows. Skylights experience three to four times as much

sunlight as vertical windows that face south.

-- --

Southern windows are also much easier to shade with an overhang. As the sun path diagram shows, when sunlight enters the southern windows in summertime, the sun is very high in the sky; thus a short horizontal overhang will cast a long vertical shadow. However, in the morning or afternoon, when the sun is beaming into the east and west windows, it is so low that only a very long overhang will provide adequate shading. Obviously, skylights present even greater difficulties. You should seek to
minimize east and west windows as well as skylights.

Sun Path Diagram for Georgia
14

You should also install an overhang or other shading device over all south-facing windows. As a general rule for Georgia, every one foot of horizontal overhang will adequately shade about 3 feet of vertical wall. Thus, if the base of the window you wish to shade is 8 feet from the bottom of the overhang, you would need a 2-foot, 8inch overhang.
Proper use of vegetation can keep your site cooler in the summer and warmer in the winter. Large canopy trees, such as oaks, can shade the roof and entire south side of a house. You should shade the south side of the house only with trees that lose their leaves by November. Low-branching trees, such as dogwoods, fruit trees, and evergreens, and trellises on which leafy vines grow can keep the low sun off of the east and west walls. Proper placement of trees can direct prevailing winds through the house in the summer and can protect the house from cold winds in the winter. Bushes skirting the house tend to trap a protective cool air layer in the summer and a warm air layer in the winter. During the warmer months, a wellshaded lot can be 10 or 15 degrees cooler than an unshaded lot.
If your house has inadequate shading, devices such as exterior operable shutters and interior roll-down shades will prevent excessive heat gains. Reflective film is another option that preserves the view out the window; of course, it should never be installed on a south-facing window that receives sunlight in the winter.
Garage Shades West Side
Windbreak of Evergreens
Ventilative and Convective Cooling Adequate ventilation is perhaps the most important aspect of passive cooling.
Air movement induced by ventilation evaporates perspiration, creating a cooling effect. For example, a well-shaded house with an indoor temperature of 850F and little or no air movement is uncomfortable. If ventilation is induced and that 850 air moves at 200 feet per minute, or a little over 2 miles per hour, you would perceive a .50 drop in temperature.
15

Trees, topography and the house design itself can be used to encourage summertime ventilation. Throughout most of Georgia, the best location for a house is on a south-facing slope. The house will be open to the more prevalent southern and eastern summer breezes and will be protected in the winter from prevailing cold winds that blow from the north and northwest.
Trees, as mentioned earlier, can funnel breezes and direct them toward the area to be ventilated. They can also provide a shelter belt to protect a home from prevailing winter winds. Breezeways and long, narrow house design can encourage air flow through a house as well.
Ventilation of a home's attic is almost as important as ventilation within the living space. Attic spaces are a major source of heat build-up; they often reach temperatures exceeding 110F. Unless a means of ventilating this trapped air exists, its heat will radiate into the building interior. Gable or roof vents will vent the overheated attic air to the outside; however, soffit vents located under the eaves must be present to supply new air to the attic. If the soffit vents are blocked or do not exist, proper ventilation of the attic will be hampered. Care must be exercised when insulating a roof near the soffit to ensure unobstructed ventilation.

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A good rule of thumb to follow for roof vents is to provide not less than one square f9ot of screened or louvered vent area for every 150 square feet of roof area. As an added feature, white, reflective shingles or roofing surface can further reduce the summer attic temperature.
One final step that can reduce roof and attic temperatures very effectively is evagorative roof cooling. Large expanses of asphalt and gravel roof areas can exceed 165 F in temperature. By installing copper water lines equally spaced on a roof and misting the roof surface with intermittent spraying, surface temperatures can drop to 90F. Such a tremendous reduction in temperature will lower the air conditioning load considerably.
16

Most of the cooling techniques discussed thus far have been anti-solar -protecting the house from the sun. One design that is able to use the sun's power in the summer is the solar chimney. The solar chimney is basically an air collector that is extremely well insulated from the living space itself. Air in the chimney increases rapidly in temperature as the summer sun shines. The high internal temperature, sometimes exceeding 160, contains enough driving force to rise rapidly through an exhaust vent at the top of the collector. As the super-heated air rushes out of the solar chimney, it pulls in air from the living space below and acts as a solar-powered attic fan. Vents open to the basement, to an exterior shady area, or to earth cooling tubes allow air to enter the house, replacing the air that enters the chimney.
The solar chimney allows the sun to help correct the overheating problems it has created. Other passive designs, such as sunspaces and thermal storage walls, can operate as a solar chimney in the summer. However, our climate has relatively small differences between daytime and nighttime temperatures in the summer. Therefore, a sunspace that receives direct sun during a summer day will not experience a cool enough night during which to exhaust the heat it has acquired. The net result is that the sunspace, unless properly shaded, provides more heating than cooling.
A major problem in designing solar chimneys is how to prevent stagnation. Although the forces within the chimney are powerful, a slight, four-mile-per-hour breeze opposing the solar-heated air's exit from the chimney will prevent proper ventilation. If stagnation occurs, temperatures inside the chimney can exceed 3QOOF. At such high temperatures, materials composing the device can deteriorate, and more seriously, the device could ignite. With wise design, stagnation can be prevented. Turbine ventilators, cupolas, and other designs will enable opposing breezes to enhance rather than inhibit ventilation.
A solar chimney can serve as a multi-purpose device. By changing the dampering system in the winter, solar chimneys can become air collectors which use blowers to move the solar-heated air into basement storage bins. Water tanks located near the exhaust vents for the chimney can provide a major share of the home's domestic hot water requirements.
Exhaust Vent
Duct from Storage in Winter
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Dehumidification
In the summer months, humidity control can be an important factor in creating a more comfortable environment in a home. Active, mechanical dehumidifiers work well and are an energy efficient alternative to air conditioning. A passive concept currently in the research stage is the use of dessicants, which are moisture-absorbing materials such as drying salts. As humid air comes in contact with the dessicants, it gives up its moisture. An obvious question is how to dry the dessicants once they have become saturated. Another problem is that as the dessicant absorbs moisture, its temperature can increase as much as 3QOF. The result is hot, dry air. These and other design problems are currently under investigation.
Underground and Earth-Sheltered Houses
An earth-sheltered house is either banked on one or more sides with earth, or built partially or entirely underground. Earth sheltering reduces the need for energy to heat and cool the building by (1) preventing the leakage of air out of and into the building, and (2) placing a barrier between the walls of the building and the extreme outdoor air temperatures. In most areas of Georgia, the temperature of the ground below the frost line remains between 5QOF and 600F year-round at depths between 6 and 12 feet.
Earth sheltering does not need to result in a dark or damp environment. On the contrary, by exposing the south-facing wall to the outdoors and making wise use of skylights or clerestory windows, an earth-sheltered home can be bright, airy and solar-heated. These buildings also have other advantages, such as long life expectancy due to their heavy, masonry construction, low maintenance, fire resistanc~, reduced noise levels, and increased comfort because of minimal temperature swings and few drafts. Their construction, however, demands more than that of aboveground structures; the services of an architect or engineer are usually required during the planning stages.
The building site is central to the planning of an earth-sheltered home. Soil and ground water conditions will determine structural and waterproofing requirements. For example, some soils are more susceptible than others to expansion when wet or frozen and will place more demands on the strength of the building. An engineer or soil-testing firm may be needed at this critical stage in the design phase.
The topography of the site -- the lay of the land -- will affect wind flow and drainage patterns, and will determine how easily the house can be surrounded with earth. A modest slope requires more excavation than a steep one, and a flat site is the most difficult, needing extensive removal of earth. It is easier to berm homes located on flat ground. Berming is the practice of banking earth up against the wall of the house.
The design of an earth-sheltered house can be varied to suit the tastes of the occupant while making the best use of the building site. When a house is built almost entirely underground, the first consideration is to provide natural light and solar heat to the living and sleeping spaces. Once again, an exposed, glazed south-facing wall is an excellent approach. The floor plan is arranged so that the main spaces share light and heat from the southern exposure.
Another approach is the central atrium, which allows for a floor plan that surrounds an outdoor space on three or four sides. The strategic use of clerestories and skylights will also allow more latitude in the arrangement of interior spaces. A properly executed design will leave the occupant with the feeling that there is very little difference from living above the ground.
18

The Earth-Bermed Colonial
The Undergrotmd Ranch Home
Earth Cooling Tubes
Earth cooling tubes are currently receivmg a great deal of attention as an alternative to conventional air conditioning. While the concept of routing air through underground tubes or chambers to achieve a cooling effect is theoretically sound, little information on the practical application of the concept is available. In the absence of sufficient field data, it is difficult to assess such factors as system reliability, cooling and dehumidification capacity, long-term performance, and potential hazards. Organizations such as the Southern Solar Energy Center in Atlanta are researching earth cooling tubes to understand their performance further.
In general, the temperature of earth at depths of 20 to 100 feet is fairly constant and 3 to 50F higher than the mean annual temperature at the site. (Mean annual air temperature for Atlanta is 60.80F.) At depths less than 20 feet, earth temperatures are strongly influenced by air temperatures and vary during the year. At the surface, earth temperatures follow air temperatures quite closely. The amplitude (range) of temperature variations decreases at greater depths to a value of almost zero at 20 to 25 feet for average conditions. Temperature waves move from the surface downward into the earth, lagging behind the mean air temperature by about one week per foot of depth.
Earth temperatures and earth cooling tube performance will vary significantly from sunny locations to shaded locations. Where possible, the tubes should be routed through shaded areas protected by vegetation, and inlets should be located to take advantage of cooler air found in the shade. The tubes should be located between 6 and 12 feet below grade. Cave-ins are a hazard at these depths and appropriate precautions should be taken.
Earth cooling tubes may be routed in two configurations: open and closed loops. Op~n loops bring outside air into the house through the tubes, while closed loops reci~cul~te ~nd c?ol interior air. Where ambient temperatures are high and ventilatiOn air requirements are small, a closed-loop system should be considered. In gen~ral, a set of .shorter tubes is more desirable than a single long tube having equivalent length, I.e., two 60-foot tubes are preferable to a single 120-foot tube.
19

Optimum tube diameter varies widely with tube cost, trenching cost, method of flow induction, flow velocity, and flow volume. For most applications, diameters between 4 and 12 inches appear to be most appropriate.
The main considerations in selecting tube material are cost, strength, corrosion resistance, availability, and durability. Tubes made of a variety of common materials such as aluminum and plastics have been used. The choice of material (and consequently the thermal conductivity of the tube wall) has little influence on thermal performance. Tubes made of plastic material may experience only a 10 percent performance penalty as compared to metal tubes.
A great deal of information needs to be developed before earth cooling tubes can be considered a practical cooling technique. Simulations, system studies, and discussions with designers and system owners indicate that earth cooling tubes do provide a workable method of space cooling. However, potential output is much lower, and the design difficulty greater than generally suspected. Considering current electric power rates and the cost of materials and labor, it is unlikely that an earth cooling tube installation can be justified on economics alone as a replacement for conventional air conditioning.
Further study is required to clarify output and economic issues, and to determine optimal tube design and operation. The designer needs a method of obtaining reliable estimates of earth properties, particularly temperatures. Closedloop systems which circulate either building interior air or a liquid isolated by a heat exchanger deserve further study. Potential hazards due to growth of microorganisms within the tubes must be assessed. Until such information is developed, any approach to the use of cooling tube systems must be considered largely experimental.
Combined Systems
Of course, a home need not limit itself to one solar design. You can use combinations of the options discussed to provide most of your home's heating, hot water, and cooling needs.
Active Solar Heating

--------'~

Sunspaces

Convective Loop

20

Thermal Storage Wall Thermosyphon Water Heater

Sunspace

Active Water Heater Thermal Storage Wall

21

Direct Solar: References
Energy Efficient Design

Sunspaces and Solar Greenhouses

Building and Marketing the Energy Conserving Home in Georgia 1980. Georgia Office of Energy Resources, 270 Washington St., s.w ., Room 615, Atlanta, GA 30334. FREE.

Sunspaces for the Southeastern United States. u.s. Department of EnergyRegion IV, Office of Appropriate Technology, 1655 Peachtree Rd., N.E., Atlanta, GA 30367. FREE.

Low-Cost Energy-Efficient Shelter for the Owner and Builder. Eugene Eccli, editor. Rodale Press, Emmaus, PA 18049.

The Food and Heat Producing Solar Greenhouse. Bill Yanda and Rick Fisher. John Muir Publications, Inc., P.o. Box 613, Sante Fe, NM 87501.

Passive Solar Design
Passive Solar Design Handbook, Vol. I and 11. National Technical Information Service, u.s. Dept. of Commerce, 5285 Port Royal Road, Springfield, VA 22161.
The Passive Solar Energy Book. Edward Mazria. Rodale Press, Emmaus, PA 18049.
Solar Retrofit: Adding Solar to Your Home. Daniel K. Rief. Brick House Publishing Co., 34 Essex St., Andover, MA 01810.

The Complete Greenhouse Book. Peter Clegg and Derry Watkins. Garden Way Publishing, Charlotte, VT 05445.
Earth Shelter Design
Earth Sheltered Housing Design. The Underground Space Center, University of Minnesota. Van Nostrand Reinhold Co., NY, NY.
The Underground House Book. Stu Campbell. Garden Way Publishing, Charlotte, VT 05445.
Insulating Shutters and Shades

Active Solar Design
Build Your Own Solar Water Heater. Florida Conservation Foundation, Inc., 935 Orange Ave., Winter Park, FL 32789, 1976, 25pp, $4.

Insulating Window Shade. Ray Wolf. Rodale Press, Emmaus, PA 18049.
Thermal Shutters and Shades. William Shurcliff, Brick House Publishing Co., 34 Essex St., Andover, MA 01810.

Hot Water From the Sun. Superintendent of Documents, U.s. Government Printing Office, Washington, D.C. 20402.

Moveable Insulation. William K. Langdon. Rodale Press, Emmaus, PA 18049.

How to Buy Solar Heating...Without Passive Solar Home Plans

Getting Burnt! Malcolm Wells and

Irving Spetgang.

Rodale Press, Passive Solar Good Cents Home Plans.

Emmaus, PA 18049.

Georgia Power Company. This design

portfolio is available free of charge

The Solar Decision Book: Your Guide from the local Georgia Power Co. of-

to Making a Sound Investment. Richard fices.

H. Montgomery. Dow Corning Corpora-

tion, Midland, Michigan 48640.

Solar Homes for the Valley. Tennessee

Valley Authority. This design portfolio

Active Solar Energy System Design is available free of charge from TVA,

Practice Manual. National Technical Publications Staff, 400 Commerce

Information Center, u.s. Dept. of Com- Ave., Knoxville, TN 37902, or by call-

merce, Springfield, VA 22161.

22 ing toll free, 1-800-251-9242.

Wood Stoves and Fireplaces
Many individuals, particularly those living in rural areas, use wood fuel to provide their heating needs. The widespread availability of wood, increasing price of other fuels, and the incentives offered by groups such as the Tennessee Valley Authority have influenced many Georgians to install wood stoves, wood furnaces or energy-efficient fireplaces. Wood furnaces and stoves are more efficient than fireplaces, but many people prefer the romance of dancing flames to the sight of a black, cast iron stove.
Before switching to wood, consider the lifestyle changes you will have to make. Are you willing to put in some hard work to gather wood? Is a high, medium or low heat setting sufficient for you rather than the precise temperature control of conventional fossil fuel heating systems? Do you want the cheery warmth of a wood stove even if it means intermittent stoking, cleaning the flue and emptying ashes? Wood heat can save you money, especially if you cut your own firewood. It can also give you a n.i .:e feeling of energy independence.
If you choose to adopt wood heating, you must be certain that the system is installed properly. The stove must also be operated safely. There have been numerous cases of families forced from their homes when their poorly designed or installed wood-burner caught the house on fire. If a good wood stove or furnace is installed, operated and maintained carefully, safety should not be a problem.

Wood Energy: References
Firewood and Forests

Firewood for Your Fireplace. Warren L. Donnelly, 3211 E. Fountain Blvd., Colorado Springs, CO 80901.

How to Select, Cut, and Season Good Firewood. John Vivian, Customer Service Dept., Stihl, Inc., P.o. Box 5514, Virginia Beach, VA 23455.
What You Should Know About Firewood -- Before You Buy. Tennessee Valley Authority, Division of Forestry, Fisheries, and Wildlife Development, Norris, TN 37828.
Stoves and Chimneys
Chimney and Stove Cleaning. c. Curtis
and D. Post. Garden Way Association Bulletin A-14, Charlotte, VT 05445.
Fireplaces and Woodstoves. M. Daniels. Bobbs-Merrill, New York, NY.
Modern and Classic Woodburning Stoves. Bob and Carol Ross. Overlook Press, Woodstock, NY.

Safe and Warm Wood Heat. Georgia Institute of Technology. Georgia Office of Energy Resources, 270 Washington Street, SW, Atlanta, GA 30334.

The Woodburners Encyclopedia. J. Shelton and A. Shapiro. Vermont Cross Roads Press, Box 333, Waitsfield, VT 05673.

The Woodburners Handbook.

D.

Havens. Harpswell Press, Brunswick,

ME.

Wood Heat. J. Vivian. Rodale Press, Inc., Emmaus, PA 18049.
Wood Heating Handbook. c. Self. Tab
Books, Blueridge Summit, PA 17214.

New Low-Cost Sources of Energy for Woodstove Know-How. P. Coleman.

the Home. P. Clegg. Garden Way Garden Way Publishing Co., Charlotte,

Publishing Co., Charlotte, VT 05445.

VT 05445.

23

Electricity from Renewable Resources
The options discussed thus far are designed to provide either space heating, space cooling or domestic hot water for a home. Several up-and-coming solar technologies can provide electricity to power appliances and provide lighting. These technologies are currently in the research stage, but they are on the brink of commercialization.

Photovoltaic Solar Cells

Solar cells, used for years to provide the electrical needs of space satellites, are coming down to earth. The price of solar cells has been declining steadily over the past two decades. Many people project that by the early 1990's, electricity produced by solar cells will cost less than electricity generated in central electric power plants.

Unlike the other technologies surveyed in this booklet, solar cells use light energy directly, instead of converting it to heat. Although there are several ways by which the sun's light energy can be directly converted to electricity, the most promising method at the present is the photovoltaic effect. Photons, the "particles" which make up a beam of light, can knock electrons loose from the atoms which they strike. The structure of the solar cell causes these loose electrons to flow toward a positive terminal. As shown in the following drawing, positively-charged holes flow in the opposite direction. The movement of these particles within the cell constitutes an electric current.
2.5 Microns
Junction

c:::=;> I ~ Ie+

Photons From Sun

c:::=;> c:::=;>

I e
!

e t
i

Silicon

c:::=;>

Electron-Hole Pairs

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Energy Out
A typical solar cell is 2 centimeters by 2 centimeters, an area of 4 square centimeters. Its power output is very small, about 0.60 watts, so many cells must be connected together for an appreciable power output. For example, a 14-volt, 1-watt panel has a surface area of about 35 square inches and weighs a little over 2 pounds.
Most solar cells are composed of silicon, the second most abundant material on the earth -- it is the major constituent of common sand. It is thus not initially expensive, but to be efficient as a solar cell, it must be absolutely pure and, more importantly, it must be in a pure crystalline form. Such crystals are at present grown very slowly in small lots.
24

There are several approaches to reducing costs. Mass production systems are being designed to optimize each operationffrom beginning with sand as the raw material to the finished cell. In a process oeing developed by Tyco Laboratories and Harvard University, a very thin die is lowerekf into molten silicon, and silicon is drawn into it by capillary action (as water goes up in a thin tube). The silicon ribbon can then be pulled slowly through the die and holds that shape as it hardens. The ribbons can be cut and fashioned into solar cells without costly grinding and polishing. Tyco hopes soon to be producing ribbons 50 to 100 feet long.
The other major direction for research and development is to improve the solar cell's efficiency. To generate 4000 Mv of electric power (about 1 percent of our present generating capacity) with 12 percent efficient solar cells would require 80 square miles of solar cell panels -- about 100,000 tons of silicon. If the cells were more efficient, less area and less silicon would be required.
Solar Thermal Systems
The energy of the sun can also generate electricity by producing very high temperatures that drive heat engines. The options that use solar thermal energy for electrical production vary dramatically in scale -- from power towers that occupy up to a square mile of land area to small-scale community energy systems that require p~rhaps_ the area of a suburban lot. All solar thermal methods concentrate sunlight With mirrors or lenses onto a device that uses the tremendous amount of heat generated to produce electricity.
At the Georgia Institute of Technology, a small power tower has been constructed. It uses a field of mirrors to reflect sunlight onto a boiler located atop a tower at the focus of the mirror field. The boiler converts water to steam that can drive a turbo-generator and produce electricity, just as in a coal or nuclear power plant.
In a smaller scale application, a parabolic dish, similar in shape to a giant, reflective salad bowl, focuses sunlight onto a heat engine. An example is a Stirling engine, which produces mechanical motion when subjected to high temperatures. The mechanical motion can turn a generator to produce electricity for nearby residences.
Solar Ponds
Solar ponds are a low-cost method for obtaining large quantities of heat from the sun. They have been developed principally in Israel, which has vast amounts of the three major requirements: cheap land, salt and sunlight.
A solar pond is a large earth basin, sealed against leaks on the bottom. Water with different quantities of salt dissolved is added in layers, with the saltiest on the bottom. A network of pipes is immersed in the saltiest layer.
Because of the difference in densities of the salty layers, they do not mix. The layers effectively insulate one another and, on a sunny day, the temperature of the bottom layer will exceed 2120F. Because of its high salinity, it will not boil. To generate electricity, a special fluid circulates through the network of pipes. As it moves through the pipes, it picks up heat and because of its low boiling point, it vaporizes. The vapor can be used just as steam to drive a turbine and generate electricity.
Solar ponds are in the research stage, but in certain regions they appear to have great promise.
25

Water and Wind Energy
Many Georgians are interested in using water power or wind energy to generate their own electricity. Georgia does have a wealth of sites for generating electric power with small dams. The Georgia Office of Energy Resources has information on small-scale hydropower in our state. In general, if you have a hydropower site, you will need to make three basic calculations -- stream flow measurement, head measurement and potential power output. A number of books written on hydropower, such as those shown in the references below, describe how to evaluate your site and how to design and construct a hydropower facility.
Unlike hydropower, wind energy is not one of Georgia's strong points. In general, average wind velocities needed to make wind energy economical should equal at least 10 miles per hour. Throughout most of Georgia, wind velocities are not that great; however, numerous citizens in the state are experimenting with wind power. The most promising areas are along the coast and in the mountains. Data is currently being gathered on wind characteristics in these regions. Call your local weather bureau for more information on wind velocity and duration in your area.

Electricity from Renewable Resources: References
Photovoltaics

"The Photovoltaic Generation of Electricity," Bruce Chalmers, Scientific American, 235 (4): 34-44, October 1976.

"Photovoltaic

Solar

Energy

Conversion," M. Wolf, Bulletin of the

Atomic Scientists, 32, 26-33, April

1976.

Photovoltaics: Sunlight to Electricity in One Step. Paul D. Maycock and Edward Stirewalt. Brick House Publishing Co. 34 Essex Street, Andover, MA 01810.

Hydropower

Marks, Vic (ed.) 1973. Cloudburst. Cloudburst Press, Ltd., Mayne Island, British Columbia, Canada VON 2JO.

Brown, L.N. 1965. Small Earth Dams: Circular 467. California Agricultural Extension, 90 University Hall, University of California, Berkeley, CA 94720.
Hamm, H.w. 1967. Low-Cost Development of Small Water-Power Sites. VITA, 3706 Rhode Island Avenue, Mt. Rainier, MD 20822.
Stoner, Carol. Producing Your Own Power. Rodale Press, Inc., Emmaus, PA.
1971. Use of Weirs & Flumes in Stream Gauging: Technical Note No. 117. World Meteorological Organization, Publications Center, P.o. Box 483, New York, NY 10016.
Wind Energy

Ovens, WG. 1975. A Design Manual for Water Wheels. VITA, 3706 Rhode Island Avenue, Mt. Rainier, MD 20822.

"Energy from the Winds" (pp. 513-551) in Energy for Survival, Wilson Clark (New York: Doubleday) 1974.

Bureau of Reclamation. 1967. Water Measurement Manual. Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

Other Homes and Garbage. Jim Leckie, et al. Sierra Club Books, 1975.
Wind and Windspinners. Michael Hackleman. Peace Press. Culver City, CA 1974.

26

The Home Solar Survey
The following survey will allow you to gauge the suitability of solar designs for your own home. You should use the survey as a workbook to evaluate your home's solar potential. Follow the steps below, or if you are unsure about using the survey, call in a local architect, builder, engineer, or well-read neighbor for assistance. To perform the survey you will need the following materials:
Compass Paper-cutting Scissors Stapler (with staples) Clear Scotch Tape Pencil Ruler Tape !Veasure FlashliJht About One Hour of Time.
Step 1: Check for Energy Conserving Features
For solar heating to work, it must be installed in an energy conserving setting. Weatherization is the first step for any building to go solar. The guidelines shown below represent the minimum needs before considering solar energy as an option:
a. Solar space heating
i. Ceiling should have an insulating value of at least R-19, which can be obtained with about 6 inches of fiberglass.
ii. The house must be properly weatherstripped and caulked. Call in a local energy contractor, an energy auditor from your local utility or another knowledgeable person if you want to know more about weatherizing your home.
iii. Install storm windows if you are located north of 320 north latitude. A large amount of glass would represent 15 percent of the floor area of the building.
iv. If you do not install storm windows, and are above 320 north latitude, do one of the following measures, if not already present, before going solar:
Insulate the floor to R-11.
Insulate the walls of the house.
b. Solar water heating
i. Place flow restrictors on all showers and faucets.
ii. Insulate hot water pipes from regular water heater and the first 4 feet of cold water pipe.
iii. Install insulating jacket around water heater.
iv. Adjust temperature setting on water heater to 1200, or if you have a dishwasher, to 1400 at most.
27

Step 2: Determine Orientation
Now that your house is properly weatherized, you are ready to investigate its solar potential. The first thing to check is where due south is. You will want your solar design to face within 200 of south.
First, find which side of the house points nearest to south. Using your compass, determine as closely as possible the direction your south wall faces.
If your south wall is more than 200 from due south, it will be difficult to make solar work for you.
Draw the house to show where it fits on the lot. Show any possible obstructions to incoming sunlight (e.g. trees, nearby buildings, etc.) Look at the example on page 31 to help you as you conduct your own solar survey.

Step 3: Assemble Solar Site Analyzer

'-'--

For each of the designs you are considering, you must determine whether they would be shaded when you need them. The solar site analyzer shows the position of the sun at all times here in Georgia. The analyzer, included separately with this booklet, contains instructions on its assembly and use. Follow these carefully, and you will have a useful device that can assess the solar potential of any site in Georgia.

28

Step 4: Draw Floor Plans and Check for Shading
Draw a plan for each floor of the house. As shown in the example on page 31, show where you would be interested in applying solar. For the locations you are considering, you need to determine how much incoming sunlight is obstructed. For space heating, you are mainly interested in the winter sun position; of course, you will want to know how well your space heating design will be shaded in summer.
If you are considering solar water heating, you will want to know the degree of shading all year long. For each of the locations you are considering for solar designs, use the solar site analyzer. Using the chart below, fill in the times when the sun will be blocked. If a tree or other obstruction is a problem, you will need to decide whether it is expendable. If you determine that it is (make sure you check with other family members first), adjust the shading calculations accordingly.

Site Type of System Planned

Winter

A B
c
D E F

Times Site is Shaded Sering/Fall
29

Summer

Step 5: Select Solar Designs
Now you know which of the sites that you are considering are feasible based on criteria of orientation and shading. Sit down with your family and decide which of those that look promising you prefer. Draw a final set of floor plans with the solar options you will investigate further. Now you are ready for the design stage.
The next two booklets in this series describe the design process and include details of numerous solar options. You may choose instead to begin at once with a professional designer or contractor. The next section discusses some considerations , before entering into an arrangement with a solar professional.
30-

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--

How much will solar cost?
Naturally, most homeowners are concerned about rising energy costs and how solar can help reduce them. However, it is difficult to make generalizations about the cost of solar and its performance for any individual home because so many factors must be considered -- levels of insulation, solar access, efficiency of various designs, and perhaps most importantly, participation of the homeowner.
The best approach in deciding if solar is a good buy for your home is to talk with energy professionals -- local architects, engineers, installers and contractors. Also, ask other solar homeowners about their experiences. Frequently, they are very knowledgeable about solar energy. Finally, do some homework. There are many books available through public libraries and bookstores to help you make a solar decision.
When adding up the costs and benefits of solar, don't forget to include the federal tax credit. This credit, up to 40% of a system's cost with a $4,000 maximum value, applies for many solar systems and components. Unlike a tax deduction, which simply reduces your gross income, this credit is subtracted directly from the total federal income tax owed for the year.
There is also a smaller federal tax credit for insulation and other energy conservation measures installed on homes built before April 20, 1977. This credit is 15% of the amount invested, up to a maximum of $300.
Georgia has two other financial incentives for solar, the Sales and Use Tax Act Amendment and the Property Tax Exemption Authorization. The Sales Tax measure requires that the usual sales tax on solar purchases be paid, but allows the owner of the property to which the system is attached to file for a refund from the Georgia Department of Revenue.
The property tax exemption authorizes local governments to exempt solar equipment from property tax assessments. Many local governments have passed this legislation. Check with your local tax commissioner to see if yours has done so.
32

Where Should You Go from Here?
How to select a solar professional
Once you have selected and sketched your solar designs, it is only natural to ask, "Where do I go from here?" For do-it-yourselfers, the answer may well be to the drawing board, then on to the local building supply store. For others, there may be a need to hire a solar energy professional, either an architect, engineer, solar installer, or contractor.
Hiring a solar professional is really no different than hiring any building professional. There are standard business practices that should be followed to protect both you and the company with which you contract. However, because the solar field is new, there are a few points to keep in mind when selecting a solar professional.
Where to Start Looking
Advertisements
Search the Yellow Pages, newspapers, newsletters, and bulletin boards for names of individuals and companies doing the type of work you are seeking. Don't be suspicious of a small operation. Often, remodeling or retrofitting with solar is a relatively small project, and a small business will give you an excellent job. You should not forget the best form of advertising -- word of mouth.
Professional Societies, Associations and Energy-Related Organizations
Frequently, these groups will have a listing service for energy professionals or will know of professionals qualified to do various types of projects.
Your Bank
It is in their best interest to recommend a professional who will do a good job, especially if they are lending you the money.
Local Government Offices and Non-Profit Organizations
The Georgia Office of Energy Resources, (404)656-5176, has a listing service for energy professionals under the Residential Conservation Service. The Georgia Solar Coalition, (404)525-7657, operates a listing service for solar energy professionals -- architects, engineers, designers, installers, contractors, and builders. The National Solar Heating and Cooling Information Center, 1-800-523-2929, has a listing of energy professionals, arranged by state, for the entire country.
Follow these steps to select a skilled, reliable contractor:
Ask each prospective contractor for a list of past customers. Follow up and check these references.
33

Talk with solar professionals about their qualifications and experience to do your specific job; ask how they charge for their services -- they may charge by the hour, by the day, or by the job -- and ask how much time it will take to complete the job. Generally, architects charge a percentage of the total cost of the job (5 - 15%) and engineers, designers, and contractors charge on a bid basis for the entire job, or by the hour for smaller jobs.
Call the local Better Business Bureau and Georgia Office of Consumer Affairs, (404)-656-7000 in Atlanta or (800)-282-4900 statewide, and ask if any complaints have been lodged against the individual business or products.
What if the sun stops shining?
Needless to say, if the sun ever did stop shining we would have no use for solar ho~es. However, what if a neighbor decides to add a second story or plant a tree that blocks sunlight to your home? Solar easements can guarantee future access to the sun.
Georgia has enacted legislation allowing privately negotiated solar easements to protect a home's access to the sun. Though solar easements are valid without specific legislation, this act advertises the availability of easements and provides guidelines for their preparation.
For most residential applications, solar easements may not be necessary; nonetheless, they provide legal and inexpensive peace of mind to the solar homeowner.
What to put in a solar contract
Like hiring a solar professional, writing a contract to perform solar work should be no different than writing a contract for any construction job. Examine the written contract carefully to make sure all promises are in writing: work to be done, quality of materials, total cost, completion time, performance claims. Take your time and know what you are signing. Read and keep a copy of all papers. Some suggestions appear below:
Get all details and claims in writing on the contract. Use advertising claims and brochures as exhibits or attachments to the contract.
Be sure there is a detailed description of the job to be completed. Make sure it includes the specifications with the brand name, size of the materials and warranty.
Consider a contract with an incremental payment schedule, so you can pay only upon satisfactory completion of incremental "steps" of the job. Withhold final payment until you are satisfied with the work.
To avoid getting sued if your contractor is uninsured, make sure the contractors and subcontractors certify in writing all damage, personal damage and liability responsibilities. If they cannot or will not, get another contractor.
Secure lien waivers. In most states, anyone who does work on your house and is not paid can place a lien on your home (i.e. claim part of your property if they have not been paid). Even if you paid the contractor, the subcontractors can place a lien against you if the contractor has failed to pay them. Lien waivers should be written into your contract.
34

Make sure the bid .or estimate includes all costs, including labor and materials. Get a fixed-bid contract, if at all possible. If you must pay by the hour or some other way, put a maximum dollar ceiling in the contract.
Include a contract clause making the contractor responsible for meeting all codes, securing any required permits and meeting any other laws or rules.
Always specify the starting and completion dates for the job. You can write in a penalty for failure to complete the job on time.
Summary This bovklet has described many of the solar and renewable energy options
available fo- your home. In general, the options are simple and easy to incorporate into either u planned, new home or an existing home. However, you must be careful with the design so that you can derive maximum benefit from your solar investment. You should seek technical opinions on the design before construction begins. Then, costly revisions will not be necessary.
Once your solar home or addition is completed, you will be rece1vmg free energy. Families living in solar homes receive numerous benefits. The low fuel bills are usually the most important. As fuel costs rise, more and more people will have trouble paying their monthly fuel bills. Solar homeowners can really appreciate the free energy they are receiving from the sun.
Many solar homeowners also begin to experience a feeling of energy independence. Solar technologies are like home power plants that extract, refine and distribute the sun's energy. Families living in solar homes not only feel a sense of pride about their home energy plants, they also can point to their contribution in saving our valuable non-renewable resources -- coal, natural gas, fuel oil and uranium.
Another benefit is that solar technologies seem to multiply, not only up the block, but also within the home. When one family goes solar, neighbors wait to see how well things work and then begin to seriously consider options in their own home. Within a home, a family may first try a solar greenhouse, then a solar water heater, then convective loop heaters and so on.
Of course, solar energy systems do not install themselves. A family must learn about and discuss the various solar options, make decisions on what solar options it wants to adopt, and then personally take the steps necessary for finding designers and builders competent in solar energy work. Building a solar home is more difficult than building a non-solar home, but it can be much more rewarding.
35

Energy Information Resources
Associations and Non-Profit Groups
Georgia Solar Coalition 1103 Euclid Avenue, NE
P. o. Box 5506
Atlanta, GA 30307 (404) 525-7657
Georgia Solar Energy Association
P. o. Box 32748
Atlanta, GA 30332 (404) 894-3635
Government Agencies
Georgia Office of Energy Resources Room 615 270 Washington Street, SW Atlanta, GA 30334 (404) 656-5176
Region IV Department of Energy Public Information Officer 1655 Peachtree Street, NE Atlanta, GA 30309 (404) 881-2696

Solar Energy Industries Association of Georgia Grumman Energy Systems, Inc. First National Bank Building Atlanta, GA 30303 (404) 588-1351
Passive Solar Energy Society of Georgia (404) 378-1977
Southern Solar Energy Center 61 Perimeter Park Atlanta, GA 30341 (404) 458-8765
National Conservation and Renewable Energy Inquiry and Referral Service (800) 523-2929 (toll free)

36

Glossary

(Adapted from The First Passive Solar Home Awards.
u.s. Department of Housing and Urban Development. January 1979)

Absorption __ ratio of solar radiation Conduction . (o~ conductivity) --the

absorbed by a surface to the

transmtss10n of heat from mole-

amount that strikes it (an impor-

cule to molecule.

tant aspect of collector efficiency).

Convection -- heat transfer through a fluid (such as air or liquid) by

Absorption cooling -- refrigeration or air conditioning that uses an absorption-desorption process capable of utilizing the sun's ener-

currents resulting from the natural fall of heavier, cool fluid and rise of lighter, warm fluid.

gy.
Active solar energy system -- a solar heating and/or cooling system

Cord -- a measure of wood quantity,
1 cord =128 feet3, or a stack of
logs measuring 4' x 4' x 8'.

using mechanical methods of heat distribution.

Creosote -- Tar-like by-product of wood burning.

Airlock entry -- a vestibule enclosed with two air-tight doors for permitting entrance without tremendous air or heat exchange.
Atrium -- a closed interior court to which other rooms open, often used for sitting and plants.
Backup heating system -- a constantly available source of heat energy which is brought into operation when the solar system storage has been exhausted and the need for heat exists.
Building skin -- (see Surface-to-volume ratio).
BTU-British thermal unit -- basic heat measurement, equivalent to amount of heat needed to raise 1 pound of water 1o Fahrenheit.

Damper -- a device that opens or closes an air passageway.
Deciduous trees -- trees which shed their leaves each winter at the end of the growing season.
Degree day (DD) --the degree day is a unit of heat measurement equal to one degree variation from a standard temperature in the average temperature during one day. If the standard is 65F and the average outside temperature is 500F for two days, then the number of the degree days is 30.
Direct conversion -- generation of electricity directly from sunlight.
Direct gain-- (see page 7).

Clerestory -- vertical window placed high in wall near eaves, used for light, heat-gain, and ventilation.
Collection -- the act of trapping solar radiation and converting it to heat (also see Distribution and Storage).
Collector efficiency --the ratio of the energy produced by a solar collector to the radiant energy incident on the collector.

Distribution -- the act of moving collected heat to needed areas. (Also see Collection and Storage).
Earth berms (or berming) -- a mound of earth either abutting a house wall to help stabilize temperature inside house, or positioned to deflect wind from house.
37

Emission (or emissivity) -- the ability to radiate heat in the form of long-wave radiation.

Evergreen/coniferous trees --trees which do not shed their leaves at the end of the growing season.

Glazed area (or glazing) -- for solar

collection, glazing refers to all

materials which are transluscent

or transparent to short-wave so-

lar

radiation,

includi~

glass, plexiglass, KalwallT ,

etc.

Passive solar energy system -- a solar heating and/or cooling system using natural means of heat distribution --generally building's structure itself forms solar system.
Phase change material -- a substance used to store heat by melting; heat is released as the material solidifies.
Photovoltaic cells-- (see page 24).
Power tower-- (see page 25).

Greenhouse -- (see page 8).
Heating load -- the term refers to the amount of BTU's required to perform the task of water and/or space heating.
Heat sink -- a massive body which can serve to absorb and store solar heat.

Radiation (or radiant) -- the process in which energy in the form of rays of light and heat is transferred from body to body without heating the intermediate air.
Retrofit -- to add a solar heating or cooling system to an existing home, previously conventionally heated and/or cooled.

Heat transfer fluid -- a liquid or gas that transfers heat from a solar collector to its point of use.
Hydropower (see page 26).
Incidence angle -- the angle formed between the sun's rays and the perpendicular to the surface on which the sunlight is falling.
Infiltration -- the unwanted admittance of air through cracks and pores which increases heat transfer.

Rock bed (remote) -- a heat storage container filled with rocks, pebbles, or crushed stone.
R-value -- capability of a substance to impede the flow of heat. The term is used to describe insulative properties of construction materials (also see Thermal Resistance).
Secondary combustion -- burning the gases emitted from combustion of the wood itself.

Insolation -- sunlight, or solar radiation.
Internal mass -- massive materials with heat storage potential contained within the building as walls, floors, or free-standing elements.
Micron -- a millionth of a meter, or .00004 inches.
Moveable insulation -- insulation placed over windows when needed to prevent heat loss or gain, and removed for light, view, venting, or heat.

Selective surface coating --specially adapted coating with high solar radiation absorptance and low thermal emittance, used on surface of an absorber plate to increase collector efficiency.
Solar concentrator -- a device using lenses or reflecting surfaces to concentrate sunlight.
Solar fraction -- the percentage of a building's net heating load met by solar gain.
38

Solar gain -- the absorption of heat from the sun. The amount of solar radiation (BTU's) received on an identified surface.

Solar-thermal conversion -- the collection of sunlight as heat, which is used to generate electricity (see page 25).

Solarium (or Greenhouse, Sunspace, and Isolated Gain) (see page 8).

Specific heat -- the amount of heat

requited to raise the tempera-

ture of one pound of material

1Of. The specific heat of water

is 1 BTU/pound/OF; the specific

heat

of

concrete

is

.22 BTU/pound/OF.

Stack effect -- the ability to set up a large enough temperature difference to effect the displacement of warm air by cooler air in a thermal chimney, such that the lighter warm air rises through a distribution space. (Also see Thermal Chimney and Stratification).

Stagnation -- trapped heat, no air movement.

Storage -- One of the necessary elements in solar design; storage involves trapping heat in a heavy mass, such as concrete walls or water containers. (Also see Collection and Distribution).

Stratification _.:. the temperature dis~

tribution within a material or

substance.

A water-filled

container used in solar heat

storage usually will be warmer

at the top than at the bottom.

This difference is expressed as

stratification or layering. (Also

see Stack Effect and Thermal

Chimney).

ing unwanted heat loss and heat gain. (Smaller numbers are desirable).
Thermal chimney -- a vertical cavity through which heated air moves as a result of the stack effect. Used as a means of passive solar heat distribution or induced ventilation.
Thermal envelope -- the enclosure (usually floor, walls and ceiling) of a building.
Thermal resistance -- the ability of a substance to impede the flow of heat. (Also see R-value).
Thermal storage wall -- (see page 10).
Thermosyphon -- (see Convection).
Time-lag heating -- a process of heating a building's interior by allowing massive materials to heat up gradually and release heat slowly into the building.
Total energy system -- system for providing all energy requirements, including heat, air conditioning and electric power.
Ventilation, induced -- the thermally assisted movement of fresh air through a building. (also see Stack Effect and Thermal Chimney).
Ventilation, natural -- the unassisted movement of fresh air through a building.
Waste heat -- heat rejected by a power plant.
Water power-- (see page 26).
Wind turbine-- (see page 26).

Surface-to-volume ratio (or building skin)-- the ratio of exposed surface of a building to occupied volume. A measure of exposure to harsh climate conditions caus-

39

The Solar Site Analyzer
The Solar Site Analyzer included with the Home Solar Survey is a tool that enables you to evaluate the shading characteristics of your lot and home. The site analyzer is a simple device, but does not give 100% accuracy. It is a hand-held tool that shows the approximate position of the sun throughout the entire year. Thus, when facing due south from a particular spot, you will be able to see how much sunlight strikes that spot in every month of the year. If used according to the instructions, the site analyzer will reveal the suitability of a given location for a solar application.
Assembling the Solar Site Analyzer
The Solar Site Analyzer has two components -- a sun chart and a semi-rigid base. The sun chart is included with the Home Solar Survey packet; you must supply the base.
To make the base, start with a piece of thin boxboard, or preferably posterboard or cardboard that is thick, but flexible enough to fold and crease. Use the pattern shown below to cut, fold, and tape together the base. Follow the steps listed.
Now you are ready to make the sun chart. The chart is covered with lines that represent the sun's path during different times of the year. In order to see through it, you will need to copy it onto a transparency. Go down to your local art supply store and pick up a 10 inch by 17 inch piece of 5 mil acetate or other clear material. Using a hard marker, copy the pattern of the sun chart included in this packet onto the transparency.
The sun chart needs to be transparent so that you can see through the chart to objects that may be blocking incoming sunlight. Use the instructions below to fit the sun chart to the base of the solar site analyzer:
Step 6: Cut out the shaded portions of the sun charts.
Step 7: Fold and crease along the dashed lines on each side and at the top.
Step 8: Tape or staple the front edge (Section F) of the sun chart to the long edge of the base (Section F of base).
Step 9: Tape or staple side edges (Sections G and H) of the sun chart to the short edge of the base.
Step 10: Fold down the top section of the sun chart and tape its sides to the upper edges of each side of the chart. The drawings shown below demonstrate how the assembly of the site analyzer proceeds through the above steps:

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Using the Solar Site Analyzer
Keep several things in mind as you use the size analyzer: the base should be horizontal at all times (a level can help here; you could even make the base out of wood and use a tripod to ensure more accurate readings); the due south middle line on the base should point due south at all times-- otherwise, you will get a poor picture of how the sun actually moves; use only one eye to sight through the analyzer and keep your eye on the middle line.
When on the site, stand with your eyes on the same level and at the location you want to evaluate. You may have to crouch or stand on a step ladder to bring your eyes to the right level. The analyzer works best if you have a friend write down the readings as you call them out.
Once you are in position to begin sighting, place one eye (the open one) right at the middle line of the base. Sight along the bottom curved line (which represents the winter sun ty:>sition) and see if any objects are behind that curve. If the object is a deciduous tree (one that loses its leaves in the winter), you can disregard it unless a dense tangling of branches is evident. For any other solid objects, note the times during which the sun will be obstructed--times are indicated by the dashed lines slanting down toward the curved, solid sun path line. Call these times out to your friend.
Next, sight along the spring/fall line following the same procedure, except you must now consider deciduous trees as solid objects. Then, sight along the uppermost summer line and check for shading conditions then. After recording all the shaded times for this site, move on to the next site that you are considering. One note about sighting along the high, summer line is to keep your cheekbone touching the base and your open eye on the middle line in order to ensure an accurate reading.

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