Chapter II. Residential Energy Use 1

Energy Information Document 1028 Chapter II. Residential Energy Use 1 G. Cook, M.S. Burnett, C.J. Delaney, J.W. Milon, F.T. Plowman, K. Walker, K.E. Wood 2 PATTERNS OF RESIDENTIAL ENERGY USE Residential energy costs are one of the major household expenditures. The average Florida household spends 6 to 10 percent of its before-tax-income on energy consumed in the home annually. The growth of residential energy use in Florida is staggering. From 1970 to 1988, the total amount of energy used by the residential sector increased 89 percent. This increase is explained in part by the growth in population and a dramatic increase in number of electric home appliances. Florida s population is projected to rise from about 11 million in 1989 to 18 million by 2020 (Berg and Loungari, 1988). In 1990, Florida s growth rate exceeded 1,000 people a day. These changes have had a significant impact on the types of fuels used in residences. The use of natural gas and liquefied petroleum gas (LPG) has been declining, while electrical energy is being used in more homes as the sole source of energy. This trend reflects the versatility of electricity as a power source rather than a desire for inexpensive fuels. Between 1979 and 1989, the price of natural gas increased from $0.45/therm to $0.55/therm, or about 22 percent, while the price of electricity increased from $0.045/ KWH to $0.08/KWH, approximately 78 percent. Accompanying this switch to electricity-using appliances has been a gradual change in the personal habits of most Floridians. More attention to personal hygiene has led to increased consumption of hot water for bathing, clothes washing, and dish washing. In addition, most people are now less tolerant of hot, humid weather, and, as a result, use air conditioners more each day and more weeks each year. As a result of the increased use of energy by each household for air conditioning, water heating, refrigeration and other end uses, and, due to the shift to electricity as the principal energy source for residential use, the growth in demand for electricity by the residential sector has been phenomenal. Knowledge of energy consumption patterns in the home is helpful in determining the potential of energy conservation methods to save money. 1. This document is Chapter 2 of the Energy Information Handbook, Energy Information Document 1028, a series of the Florida Energy Extension Service, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Revised: August 1991. 2. G. Cook, Energy Specialist, Energy Extension Service; M.S. Burnett, Adjunct Assistant in Agricultural Engineering; C.J. Delaney, Visiting Energy Extension Agent; J.W. Milon, Professor, Food and Resource Economics; F.T. Plowman, Associate Professor, Home Economics; K. Walker, Assistant Professor, Home Economics; K.E. Wood, Assistant Professor, Home Economics, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611. The Florida Energy Extension Service receives funding from the Florida Energy Office, Department of Community Affairs and is operated by the University of Florida s Institute of Food and Agricultural Sciences through the Cooperative Extension Service. The information contained herein is the product of the Florida Energy Extension Service and does not necessarily reflect the views of the Florida Energy Office. The use of trade names in this publication is solely for the purpose of providing specific information. It is not a guarantee or warranty of the products named, and does not signify that they are approved to the exclusion of others of suitable composition. The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / Christine Taylor Stephens, Dean

II. Residential Energy Use Page 2 The two most significant energy consumers in the average Florida household are water heaters and air conditioners. Air conditioning is the major household energy consumer. Whole house air conditioning uses more than twice as much as a single unit. In most homes an electric water heater consumes twice as much primary energy to accomplish the same task as those units that burn fuel directly (i.e., gas water heaters). Mobile homes, which constitute about 15 percent of the dwellings in Florida, account for 15 percent of residential primary energy consumption. Mobile homes and houses built on site consume almost the same amount of primary energy per residence, although mobile homes tend to be smaller and thus consume more energy per square foot of living space. RESIDENTIAL ENERGY CONSERVATION The Comfort Zone Both temperature and humidity affect the feeling of comfort in a home. At a given temperature, increasing the humidity results in a feeling of increased warmth. There is a "comfort zone," in which the temperature and humidity are within the ranges where most people feel comfortable. In hot, moist Florida summers, a dehumidifier decreases humidity and increases comfort. An air conditioner, by cooling the air and condensing atmospheric moisture on its coils, acts to dehumidify air. Conversely, dry winter air feels warmer when moisture is added to it by a humidifier. The following sections on insulation, weatherstripping and caulking, control of direct sunlight, air conditioning, space heating, ventilation, and moisture control deal directly or indirectly with maintaining the environment of the home within the comfort zone. Insulation Types Insulation does not completely prevent heat loss; it reduces the rate at which heat is transferred through a space. The proper use of insulation in a house, apartment, or mobile home is one of the most effective means of increasing the thermal resistance of the structure (Appendix B) and reducing the cost of cooling and heating. Insulation is available in many forms such as batts, blankets, or loose fill (Table 1) and is made from a variety of different substances (Table 2). The choice of insulating material to use depends upon whether you are building a new home or improving an old one and the amount of money you want to invest to get the job done. Table 1. Form of Insulation Form Sizes Contents batt blanket loose fill foam rigid boards 4 ft or 8 ft long 15 in or 23 in wide 1-7 in thick rolls of various lengths 15 in or 23 in wide 1-7 in thick various sizes and thicknesses with or without vapor barriers with or without vapor barriers blown into walls and attics installed by contractors with or without vapor barriers Simply stated, insulation keeps heat outside the house in the summer and inside in the winter. Adding one inch of insulation to an uninsulated wall can reduce the heat loss or gain through the wall by 40-50 percent; 3.5 inches of insulation can reduce this heat transfer by 75-80 percent. An uninsulated wall with an R factor of 1.54 allows heat to flow through very easily. On the other hand, a wall with 3.5 inches of insulation and an R factor of 13.3 will substantially reduce heat loss. Concrete block walls (CBW), which are common through Florida, are very poor insulators. A typical 8 inch block has an R Factor of about 1.0. Although little can be done for existing structures, insulation can be added to the inside of the wall in new CBW structures to reduce heat loss or gain. Insulation Check-Up Before adding more insulation to a home, it is important to determine what kind of and how much is already there. In most cases, the attic can be checked easily. With an unfloored attic, measure the existing insulation with a ruler. If the type of insulation is not

II. Residential Energy Use Page 3 Table 2. Insulation Materials R-Factor Per Inch Material Thickness Type Advantages Disadvantages Vermiculite 2.4-3.0 loose fill inexpensive easy to install good for attics R-factor drops as it settles absorbs moisture not suited for walls Perlite (volcanic rock) 2.5-3.7 loose fill similar to vermiculite with higher R-factor similar to vermiculite Fiberglass 2.2-3.2 batt blanket loose fill Rock Wool 2.9-3.7 batt blanket loose fill inexpensive fire resistant durable same as fiberglass no odor if dampened irritates skin develops odor if dampened irritates skin Polystyrene (styrofoam) 3.9-5.0 rigid boards good for exterior walls and slab foundations highly combustible requires external covering Cellulose 3.2-3.7 batt blanket loose fill higher R-factor than fiber glass or rock wool doesn t irritate skin absorbs moisture supports fungal growth Urea formaldehyde 4.2-4.5 foam high R-factor fire resistant soundproof expensive installation shrinks potential noxious fumes clear, take a piece to an insulation dealer. Determine the total R factor of the insulation by multiplying the per inch R factor by the measured number of inches. A floored attic is a more difficult matter. If the boards are butted together, simply pry up a board to check. However, if the floor is tongue and groove, drill a hole in a corner and use a flashlight to see if the insulation fills up the space. If it does not, use a probe to determine how much insulation could be added. For checking the insulation in walls, it is best to use existing openings such as electrical outlets. Be sure the electricity is turned off before any work is done. After removing the cover plate from the outlet, it may be necessary to chip away at the sheet rock next to the outlet box in order to see the insulation. Use a utility knife or chisel, but do not chip away any more than will be covered by the cover plate. Use a flashlight and probe to determine the type and thickness of the insulation. Since Florida has a milder climate than most parts of the United States, it is not necessary to insulate a house to the levels required in other parts of the country (Table 3). Table 3. Minimum R Factors for Florida Homes Ceiling R-19 - R-30 Exterior Walls Wooden Frame Block R-11 R-9 Floor R-11 Installation Tips If you cannot afford to insulate your whole house, start with your attic. If the attic is unfinished, the insulation should be placed between the ceiling joists. If you have a wooden floor in your attic but do not heat this area, try to remove enough of the floor boards to get insulation underneath all of the floor boards. If there are rooms that are used and heated in your attic, put the insulation above the ceiling and behind walls that face out toward unheated areas. If there is not enough crawl space to get into the attic and insulate, or if you live in a mobile home with a flat ceiling, you can use high R factor ceiling tiles.

II. Residential Energy Use Page 4 When installing insulation wear loose fitting, old clothes, a long-sleeved shirt and gloves. Use a sharp knife with a serrated edge to cut batts and blankets. Push batts and blankets into place with a rake. A measuring tape, portable light with an extension cord, staple gun, and some plywood or boards to walk on to avoid damaging your ceiling might be helpful. If your attic does not have a floor, place batts or blankets or pour loose fill insulation between joists. Do not cover eave vents. The vapor barrier on insulation must face down. For loose fill insulation, or batts and blankets without a vapor barrier, cut clear "polyethylene" plastic into strips that fit between the joists. Put the plastic down before you install the insulation. If you are adding a second layer of insulation to the attic and using batts or blankets with a vapor barrier, slash the vapor barrier with a knife several times. This will allow the insulation to dry out if moisture builds up. Insulate the hatch cover, hot water pipes, and hot air ducts. Fill the space between a chimney and any wood framing with materials that cannot burn. Keep insulation at least 3 inches away from recessed light fixtures or other heat producing equipment. Once you have enough insulation in your attic, insulate behind walls and under floors. Many Florida homes have concrete floors and walls, so it may not be feasible in terms of cost benefit to insulate them properly. However, for houses that have a crawl space beneath the floor, insulation can be added between the joists. Insulation in batts is the easiest to use in this confined area. Any kind of wire or wood strip can be attached across the joists to hold the insulation in place. Put the vapor barrier up, toward the living space. If there is much moisture under the house, an additional vapor barrier on the ground may also be necessary. For houses that do not have concrete block walls, insulation can be added between the wall studs. If there is access to the cavities between the studs from the attic, loose fill insulation can be poured down until the cavity is filled. If the wall cavity can not be accessed from the attic cut holes every 16 inches in the walls and blow insulation into the cavities. Insulation blower units can be rented from insulation dealers or equipment rental companies. Weatherstripping and Caulking In a well insulated house, air leakage is the greatest cause of wasted heating and cooling energy. By sealing unnecessary openings and cracks with weatherstripping and caulking, you can prevent waste, lower your fuel bills, keep out moisture, and have a cleaner, quieter home. Both weatherstripping and caulking are low in cost, easy to install, and can contribute to substantial savings. This is an important step in both old and new construction A hole 10 inches long and 3 inches wide is equal to a 1/8-inch crack around a normal-sized outside door. The homeowner s goal should be to close as many air leaks as possible. Check all the outside doors of your home to see whether there are cracks where a door fits the frame and/or where the frame meets the wall. Do the same for windows and frames. On windy days, you can use a lighted candle to help find small leaks. Slowly move the candle along the door and window frames. If the flames flickers, you ve found a leak. There are many types of weatherstripping available either by-the-foot or in kits complete with seal and fasteners (Table 4). The more common types of weather-stripping are made of felt, plastic, foam, metal and vinyl. When you buy the weatherstripping in a kit, make sure it is suitable for installing around your door or window type and size. Cost, ease of application, appearance and lasting qualities should be considered. Measure around each window and door to find out how much weatherstripping is needed. Follow specific instructions given on the package for installation. Caulking is needed wherever two different materials or parts of the house meet. Caulking compounds are available in disposable cartridges made to use with a caulking gun, in bulk gallon and 5-gallon cans, in rope form that you unwind and force into the cracks with your fingers, and in squeeze tubes that work like toothpaste tubes. Use the right caulking material for the job. In the long run, it will pay to base your selection on performance characteristics rather than purchase price alone. Compounds should be selected on the basis of their ability to adhere to other materials such as wood, glass, metal, plaster, or masonry, since these materials expand and contract. Resistance to weathering, cracking, shrinkage, water and mildew are also important. Some manufacturers state the life expectancy of their product, if properly installed inside or outside the home. One of the synthetic, flexible or water base caulking products will best serve the needs of most homeowners. Butyl rubber caulk provides exterior durability, resistance to shock, heat and cold. Acrylic latex caulk is easy to

II. Residential Energy Use Page 5 Table 4. Weatherstripping for Around Doors and Windows Type Use Advantages & Disadvantages Felt Felt-metal strips Plastic or rubber foam Spring metal Tubular vinyl gasket For Bottom of Doors Metal and vinyl bottom strip Metal threshold with vinyl gasket Tacked or stapled to fill the gap where window or door meet the framework. Felt in metal strips nailed around door or window frame to seal gaps. Adhesive backed foam strips fasten to framework of door or window. Spring-activated strips of bronze that are nailed around door frame. Vinyl stripping with lip that nails to door or window frame. Metal part screws or nails to bottom of door; vinyl part seals door/floor gap. Vinyl gasket seals space between floor and closed door. Inexpensive; easy to install. Temporary; can t be used where parts slide against it. Inexpensive; not very attractive. Durable. Inexpensive; easy to install. Sticks well to wood or metal. Should not be used between sliding components. Fairly expensive; easy to install. Permanent; creates a tight seal. Inexpensive; easy to install. Use on areas hard to seal, uneven doors or windows. Extremely durable, easy to install. Effective when installed properly. Permanent; vinyl gasket may be replaced. apply with almost unlimited use, indoors and out. The bead can be smoothed with a wet finger, clean-up is fast with water, and it can be painted immediately with latex paint. Oil base caulk is good for general home use. Consult with your building supply dealer for the best caulk to use in your specific case. All types of caulking should be applied over clean, solid, completely dry material. Large cracks over 3/16 of an inch, should be filled within 1/4 inch of the surface with a backup material such as oakum or polystyrene or fiber rope. The time to caulk is during spring or early fall. Below 40 degrees F (4 degrees C), caulk may not cure properly and condensation or moisture can prevent a solid bond. Control of Direct Sunlight for Comfort You can make your house cooler in summer and reduce the cost of mechanical cooling by shading it from direct or reflected rays of the sun. External louvers or bar screens reduce direct solar heat by 90 percent for south-facing windows and they reduce direct solar heat by 50 percent or more for east and west windows during most of the day. Venetian blinds reduce direct solar heat by 25 to 50 percent, depending on the color and angle of the slats. Roof overhangs, or extensions of the roof over south walls, are usually easy to incorporate into house designs. Latitude and season of year determine the angle at which the sun s rays strike the earth at different times of day. The distance the south windows extend below the eave of the roof or horizontal overhang is the shadow height. Given a specific latitude and shadow height, the width of the overhang required can be determined (Table 5). Table 5. Overhang Shadow Factor North Latitude (degrees) Shadow Height (feet) 3 4 5 6 7 8 Width of Overhang (feet) 25 1.1 1.5 1.9 2.2 2.6 3.0 25 1.4 1.9 2.4 2.9 3.4 3.8 Overhangs can also extend east and west of the edges of a south-facing window to provide shade from midmorning to midafternoon. To calculate the length of

II. Residential Energy Use Page 6 east and west extensions needed, multiply the width of the overhang by the factor for the specific latitude (Table 6). Table 6. East and West Window Overhang Factors N. Latitude (degrees) Factor 25 2.35 30 1.85 East and west windows are more difficult to shade with overhangs than are south windows. In most cases, awnings, louvers or bar screens, trees, and large shrubs can be used effectively on east and west windows. Houses with high-pitched roofs are cooler than those with low-pitched or flat roofs. Roof slopes facing north and south are cooler than those facing east and west. Studies have shown that there is no significant difference between light and dark covered roofing. The surface texture seems to play a more important role. Smooth roof tiles reflect better than coarse shingles, independent of color. Metal or canvas awnings of light color reduce direct solar heat up to 70 percent. Awnings with open sides are best. All awnings must be wider than the windows they shade to keep the sun out longer. Conventional Air Conditioning The use of central air conditioners is increasing more rapidly than the use of window units. From 1960 to 1975, the appliance saturation of central units increased from 2.8 percent to 65.0 percent for the state as a whole, whereas window unit saturation increased from 15.4 percent to 60.0 percent. This has resulted in an increase in the percentage of the average household budget that pays for air conditioning. In 1960, air conditioning costs for the average Florida family were 6 percent of the total residential energy budget. By 1975 these costs had risen to 29 percent of the residential sector s energy use. The most important consideration in buying an air conditioner is the Seasonal Energy Efficiency Ratio (SEER). The higher the SEER rating, the less electricity the unit will use to cool the same amount of air. SEERs range between 6 and 12. Do not buy a unit with a SEER of less than 7. The units with higher SEERs are more expensive but the electricity savings is worth it. A window unit with a SEER of 12 cools 50 percent more air for a dollar s worth of electricity than a unit of the same size with a SEER of 8. The ability of an air conditioner to remove water (latent heat) from the air is important. A sensible heat (temperature) ratio (SHR) of 0.76 means that 76 percent of an air conditioner s heat removal capacity is used to lower the air temperature and 24 percent is used to remove water from the air. In Florida, using air conditioners with adequate ability to remove the latent heat is important. An air conditioning dealer can determine how large an air conditioner is needed by the size of the room. If the room s size is midway between two sizes, get the smaller of the two; an air conditioner that is too big will shut off before it removes enough humidity from the air to make the room comfortable. To reduce air conditioning costs, consider the following options. 1) Insulate, weatherstrip and caulk to reduce air conditioning costs. Heat passes easily through poorly insulated walls and attics and cool air escapes through cracks and gaps around windows and doors. 2) Close the draperies during the day to prevent solar radiation from entering through the windows and heating the living space. 3) Turn the air conditioner off or set the temperature 5-10 degrees above the normal summer setting when the structure will be unoccupied for more than a day. If mildew is a problem, install a timer on the air conditioner to run the unit for 2 hours per day to rid the house of moisture. 4) Use the exhaust fan sparingly when the AC unit is in operation. 5) Set central air conditioner units on auto for the most economical operation and humidity control. 6) Clean air filters regularly, and replace them when dirty. 7) Use household fans to distribute the cool air and improve the performance of window units. Fans located near the floor are best because cool air settles near the floor. 8) Aim the vents of room air conditioners upward for better air circulation, and keep furniture, drapes and other obstacles away from the vents. 9) install a timer control to keep the air conditioner off until shortly before someone gets home if the house is unoccupied during the day.

II. Residential Energy Use Page 7 10) Check ductwork for leaks in the evenings or on an overcast day. Leaks can be detected by feel or sound. 11) Balance the air conditioning system. Make sure that an adequate number of supply and return air grills are installed and properly adjusted. Natural Air Cooling There are a variety of naturally occurring cooling systems. Natural ventilation and solar-assisted dehumidification are two of the methods that work well in Florida. Differences in the heating of Earth s surface by the sun generate winds on both a continental and local scale. Taking advantage of the prevailing winds using building orientation, design and energy-saving landscaping techniques can be a cost effective means of cooling homes in Florida. A solar assisted dehumidification system passes the air over a desiccating agent, which dries the air. The moisture that collects in the desiccating agent is removed with solar heat. Systems that store cool night air, water or rock bed (heat sinks) and evaporative cooling systems do not work well in Florida. Conventional Space Heating Fuel consumption for space heating is subject to 1) the size and fuel type of the space heater, 2) the efficiency of the air distribution system, 3) the living area that must be heated, 4) R values of the exterior walls and windows of the building, and 5) the severity of the weather. A great deal of heat is lost through and around windows. The simplest way to reduce this heat loss is to install double pane windows, but these can be expensive. Close curtains, drapes, or window shades at night to reduce heat loss, and open, if needed, during the day to allow sunlight to enter. Use caulking or clear plastic tape to reduce the air flow from air leaks around windows. Set the thermostat at the lowest comfortable setting, usually 65-68 degrees F (18-20 degrees C). For each additional degree setting above 68 degrees F (20 degrees C) about 5 percent more energy will be consumed. Turn the thermostat to 55-60 degrees F (12-16 degrees C) if you will be gone for a few days. Warm air rises up a chimney. Close the damper when the fireplace is not in use. Do not operate the central heating system and the fireplace at the same time. Close doors and vents to unused rooms. Do not block vents with furniture or drapes and check the ductwork for leaks. Portable electric heaters can be an efficient way of heating small areas. Do not try to use the stove to heat the house; this is a very inefficient heat source. Consider using natural gas as a heat source. Natural gas generates less acid rain or carbon dioxide per Btu than coal or petroleum oil. In Florida, 57.7 percent of our electricity comes from coal and petroleum. Electric blankets are a good investment. They use only small amounts of electricity and allow you to reduce the thermostat to 60 degrees F (16 degrees C) at night while staying warm. Overview Passive Solar Space Heating Sunlight is an abundant resource in Florida. Winter skies are especially clear, and temperatures are not extremely cold. These conditions lend themselves to exploiting the free flow of solar energy by using solar space heating. A system designed to provide 75 percent of the winter heating needs with solar energy, with the remaining 25 percent supplied by a back-up system, is cheaper than a system that provides 100 percent of heating needs with solar energy. Designing a solarheated home that provides 100 percent of the heating needs during the most extreme cold period of the year means that for most of the year, the system is oversized. Often the collector size for a 100 percent solar heat system is twice that of a 75 percent solar heat system. Passive solar heating uses nonmechanical means to collect solar energy and to transfer it to the living space. Passive systems are composed of a south-facing glass area that collects solar energy, and a thermal mass that absorbs, stores, and distributes the captured heat. There are two types of passive solar heating systems: direct gain and indirect gain.

II. Residential Energy Use Page 8 Direct Gain Systems In direct gain passive solar heating systems, the living space itself is directly heated by sunlight. Collection, storage, and distribution of the solar heat are all accomplished by the living space. These systems work well in both sunny and cloudy regions. Heat storage is accomplished by masonry or water containers integrated into the dwelling structure. Masonry heat storage necessitates a heavy structure with masonry walls and floors. Interior water wall storage may be used with wood frame construction. Use of movable insulation over windows at night reduces heat loss. Shading devices prevent summer overheating. Reflectors help reduce the window area necessary to heat a given space. Ventilating devices help control temperature. If 0.05 to 0.10 square feet of south-facing windows are constructed for every square foot of floor area, the average temperature inside the structure from direct solar gain will be 56 degrees F (13 degrees C) for most of the winter in Florida. A solar window that is as much as 25 degrees to the east or west of south still intercepts 90 percent of the sunlight striking it. Recessed windows and wood sashes help reduce heat loss. Passive solar collectors integrated into the roof allow sunlight to be distributed to any part of the building, allowing for flexibility in locating thermal mass. Chances of sunlight blockage by obstructions are also decreased. A clerestory is a vertical window projecting up from the roof plane. A clerestory should be located at a distance from the interior thermal storage wall equal to one to 1 1/2 times the height of the base of the clerestory. The ceiling of the clerestory should be light in color; its roof should overhang to provide summer shading. A sawtooth is a series of clerestories, each directly behind the other. The angle of each clerestory roof (measured from the horizontal) must be equal to or less than the angle of the sun on December 21, so the clerestories do not shade each other. Horizontal skylights must be large and must employ a reflector to significantly contribute to heating. All skylights should have shading devices to prevent summer overheating. For masonry heat storage, interior walls and floors should be of masonry at least four inches thick. Sunlight striking masonry surfaces should be diffuse. This can be accomplished by using translucent glazing on many small windows, or reflecting sunlight off light-colored surfaces. Each square foot of direct sunlight should be diffused over more than nine square feet of masonry surface. Masonry floors should be dark and not covered with wall-to-wall carpeting. Masonry walls can be any color, but non-masonry surfaces should be light-colored. Sunlight should not strike dark masonry surfaces for prolonged periods of time. Thermal storage capacity should be slightly oversized to account for cloudy days and the exterior surface of the thermal mass must be insulated to prevent heat loss. Interior water walls should be located where they receive direct sunlight from 10 a.m. to 2 p.m. If the wall is not exposed to direct sunlight, four times as much storage will be necessary. The container surface should be dark. Provide 7 1/2 gallons of water per square foot of solar window. The thermal storage capacity should be slightly oversized to account for cloudy days. Black containers are most efficient, but blue and red are only 10 percent less efficient. Indirect Gain Systems In indirect gain passive solar heating systems, the sunlight heats the thermal mass, which then radiates heat into the living space. There are three basic types: thermal storage walls, isolated-gain systems, and roof ponds. The maximum distance of effective heat radiation from a solar wall is only 15 to 20 feet. This necessitates a linear, east-west oriented house plan. Windows may be provided in the otherwise opaque wall to allow sunlight to reach the living space. Double glazing or insulating shutters reduce nighttime heat loss. Thermocirculation vents at the top and bottom of the wall, and insulating panels or drapes, help control temperature. These vents should each have an area of one square foot for each 100 square feet of wall area. Use of 0.10 to 0.15 square feet of masonry wall or 0.08 to 0.12 square feet of water wall, per square foot of floor area should maintain a comfortable internal temperature under Florida conditions. For masonry thermal storage walls the recommended thickness of the wall is 8 to 12 inches for adobe, 10 to 14 inches for bricks, and 12 to 18 inches for concrete. Outside face of the wall should be dark. The greater the wall thickness, the less the indoor temperature fluctuates.

II. Residential Energy Use Page 9 For water thermal storage walls the recommended thickness of the wall is six or more inches. After six inches, little increase in performance occurs. A roof pond built on the roof of a building captures heat during a winter day and insulates the building at night. In the summer, the roof pond is insulated during the day and exposed during the night to contribute to cooling. The pond surface should be exposed to direct sunlight between 10 a.m. and 2 p.m. in the winter. Ponds are typically 6 to 12 inches in depth, and the building structure must support from 32 to 65 pounds of dead load per square foot. Daily temperature fluctuations are slight in a properly designed system. Ponds are often double-glazed with inflated plastic air cells. Roof ponds are inexpensive and effective. In humid climates, spraying or flooding the outside surface of the enclosed ponds provides four times as much cooling, as night sky radiation alone. Isolated-gain passive solar heating systems are separated from the living space. A natural convective loop connects a flat plate collector with a thermal storage bin. Water or air with rock bin storage are two types of heat transfer and storage mediums. Heat is drawn from the thermal storage when needed for the living space. Attached Greenhouses An attached greenhouse is a combination of direct and indirect gain systems. Sunlight directly heats the greenhouse space, and the common wall shared with the dwelling radiates heat to the living space. About 0.25 square feet of double-glazed glass per each square foot of floor space to be heated for a common masonry wall or 0.20 square feet for a common water wall should work well for Florida conditions. The storage wall should be dark in color and be exposed to direct sunlight. Exterior and interior venting allows for temperature control of both the greenhouse and living space. An attached greenhouse on a wood-frame dwelling stores little solar energy, and doesn t contribute to nighttime heating. However, the greenhouse serves to protect the common wall from heat loss. A common masonry thermal wall employed alone doesn t greatly dampen temperature fluctuations. The volume of water in a common water thermal wall determines the temperature fluctuation of both the greenhouse and living space. Use of at least five gallons of water per square foot of south-facing glazing adequately dampens fluctuations. An active rock storage system with passive heat distribution is another means of collecting and distributing warm air. The warm air is circulated by a fan to a rock bed in the crawl space below the living space. A thermal wall is not needed between the greenhouse and living space. At least one-half of the floor s surface area must act as a heating source for the living space. Each square foot of south-facing area requires about 3.4 cubic feet of fist-sized rock. Basic design principles (Fisher and Yanda, 1976): 1) Orient the long axis within 20 degrees of the eastwest axis. 2) Use at least two layers of glass and/or plastic glazing on the south wall and roof, with insulation along the north wall and roof and east and west walls. 3) Stimulate natural convection currents with top and bottom vents for warm air distribution. 4) Weather-strip doors and vents to prevent unwarranted heat loss. 5) Use large quantities of rocks or water in containers as heat storage. This helps maintain heat at night and contributes to cooling during the day. 6) Insulate the south-facing glazing at night. Materials cost $3 to $7 per square foot of greenhouse floor for owner-built, solar-heated greenhouses. Contractor-built greenhouses start at $5 per square foot. Unassembled commercial kits are available from $15 per square foot. Active Solar Heating Active solar heating uses mechanical means to collect solar energy and transfer it to the living space. Active systems are composed of 1) a solar collector that heats a transfer medium (Table 7), pumps, and fans, and circulates the warmed transfer medium to a heat storage unit, and 2) a delivery and control system that distributes the heat to the living space. A flat plate collector consists of clear glazing, an absorber plate, and insulating housing. The glazing is one or two layers of glass, fiberglass, or plastic. The absorber is metallic plate painted black. The insulating housing should be better insulated than the house, since the collector temperature must exceed the temperature of the living space (Keyes, 1979). Anti-reflective coatings and selective surfaces, although effective, are expensive

II. Residential Energy Use Page 10 Table 7. Heat Transfer Media Media Advantages Disadvantages Air Liquid Costs 1/4 price of liquid system Less collector area required More effective at lower temperatures High extraction efficiency from storage Doesn t freeze Corrosion free High collector efficiency Supplies domestic hot water and short-lived (McDaniels, 1979). A vertical vane enhances increased performance, especially for morning and late afternoon sun and cloudy days. Use of a horizontal reflector at the base of a solar collector increases the heat gain by 25 to 30 percent. Advanced collectors, such as concentrator, compound parabolic, and evacuated tube collectors, are expensive devices designed for high temperature processes, and are not appropriate for solar space heating (Watson, 1977). A collector s optimum orientation is 10 degrees west of due south, but within 30 degrees of south is acceptable. Optimal tilt is equal to latitude, plus 15-20 degrees. Ground-mounted units receive 5-30 percent more sunlight than roof-mounted units, because they receive more diffuse radiation. However, a roofmounted unit may raise the collector out of the shade of nearby obstacles (Keyes, 1979). The storage system should store about 1 1/2 days worth of collected solar energy, and should be better insulated than the house it is heating to maintain a higher temperature. Pebble bed storage is used with systems that use air as a heat transfer medium. Rock has 1/5 the heat capacity per weight, and 1/3 the heat capacity per volume, of water. Thus, a pebble bed storage system requires three times the volume of a water storage system of equal storage capacity. The heat exchange ability of rock is proportional to its surface area. Smaller rocks provide more resistance to air flow and require increased fan power. Commonly, rocks from 1 Requires more electric power electric power Low collector efficiency Size of rock bin storage must be 3 times the size of a water tank Requires separate hot water heater Need 2/3 more collector area than air system Inefficient heat exchange process Requires frost and corrosion protection to 5 inches are used. If the rocks are less than 1 1/2 inches, convection currents in the heat storage are avoided and less heat is lost when the system is not being drawn upon. An advantage over water systems is that rocks neither freeze nor leak. Water tank storage is used with systems that use water or water/antifreeze as a heat transfer medium. Water has a high heat capacity; a water tank storage system needs to be only one-third the volume of a pebble bed storage system of the same storage capacity. Although water holds more heat per volume than pebble beds, it loses heat much faster due to convection currents in the tank. Water tanks need to be well insulated, and are often surrounded by rocks to provide extra storage capacity. Additional problems with water storage systems are freezing, corrosion, and leaks. Chemical storage systems hold large amounts of heat in a small volume. Glauber s salt (sodium sulfate decahydrate) is suspended in water. In daytime, when the temperature of the storage liquid reaches 90 degrees F (38 degrees C), the crystals melt, absorbing a large amount of energy. At nighttime, as the temperature drops below 90 degrees F (38 degrees C), the stored energy is released. The heat capacity per weight of a chemical phase change storage is fifty times that of water and 250 times that of rock. Problems encountered include supercooling, where the salt fails to resolidify and release its energy as it reaches its freezing point, container failure due to corrosion, and the necessity of replacing the liquid after 400 phase changes due to material breakdown. The heat distribution system extracts heat from storage and delivers it to the living space. Solar heat storage systems commonly operate at a lower temperature (85-120 degrees F) (29-49 degrees C) than do conventional heating systems (180 degrees F) (82 degrees C). Fans (1/6 to 1/2 hp) blow air from either the collector itself or from the pebble bed heat storage through ducts to registers in the living space. A larger than conventional duct size is required to move the larger

II. Residential Energy Use Page 11 volumes of lower temperature air necessary to delivery the same amount of heat from a solar system. This system requires two sets of thermostats. The house thermostat directs warm air into the house. The differential control thermostat compares the temperatures of the collector output and the cool end of the storage unit: if the storage is cooler, fans force air from the storage to the collector in a loop. Care must be taken in register placement so that occupants are not exposed to drafts of 90 degrees F (38 degrees C) air blowing into the living space. Pumps (1/30-1/10 hp) circulate water from the top of the storage tank through baseboard heater or radiant floor/ceiling in hot water circulation systems. The pumps require only 1/5 as much electricity as the fans of a forced air system, but this economic advantage is offset by the need for antifreeze. Baseboard heaters commonly available are designed to operate at 130 degrees F (54 degrees C), while the solar-heated water in storage has a temperature of 85-120 degrees F (29-49 degrees C). The conventional fin tubes function at a lower efficiency at the lower temperature. Thus baseboard units must be larger. Heat Pumps A heat pump operates very much like a refrigerator or an air conditioner. A heat pump uses electricity to run a compressor that pumps heat from one place to another. In the summer, a heat pump removes heat from the conditioned living space and discharges it to the outside. In cold weather, the process is reversed so that the heat pump removes heat from the outdoor air and transfers it to the living space of a home. All air, even the coldest, contains some heat from molecular motion. The heat pump, removes some of this heat and pumps it into the house. While all air contains some heat, it should be noted that heat pump efficiencies decrease dramatically when temperatures are substantially below 40 degrees F (2 degrees C). During the heating phase, low temperature freon is pumped through the evaporator where it absorbs heat from the source (air or water) and evaporates. It is then compressed to a moderately high temperature and pressure, and pumped through the condenser where it releases the heat to the room as it returns to a liquid state to begin the cycle again. A fan blows air over the condenser and circulates warm air through the room. During the cooling phase, this process is reversed. The room becomes the source from which heat is extracted and the outside becomes the sink. If you currently heat your home with electricity, replacing that system with a heat pump could significantly reduce your electric heating bill. This is because of the relatively small amount of mechanical energy required to transfer a given amount of heat from an area of lower temperature to an area of higher temperature. Under optimum conditions a heat pump will supply 3 or 4 units of heat for every unit of mechanical energy supplied as work. Thus, you have a Coefficient of Performance (COP) of three to four. In comparison, an electric resistance heating system has a COP of one. It should be noted that at current fuel prices of number 2 heating oil and natural gas, heating systems using these fuels may be more economical than a heat pump. In many cases the best choice depends on the particular circumstances in your area. Look into the matter carefully and don t rely on the first opinion you hear. While heat pumps can contribute to significant savings on electric heating bills in certain climates, they do have some major disadvantages. In Florida, heat pumps are usually sized in accordance with the required summer cooling load. When they operate in reverse cycle on a cold day, they may not produce enough heat, thus necessitating the use of a back-up system to keep the living area at a comfortable temperature. If a heat pump is sized to handle the heating required on the coldest days, it produces too much cooling during summer days. Short bursts of cooling with an oversized unit may keep the room temperature at a desired level, but the unit will not have operated long enough to reduce the humidity. There must be a trade-off in the sizing requirements of a heat pump for the heating and cooling season in Florida. It is encouraging to note that there are plans for variable capacity heat pumps in the design phase. These machines can be operated at full on cold days and at reduced capacity on warm days. This alleviates the problems associated with oversized cooling units and still keeps the additional cooling capacity in reserve. The initial cost of a typical heat pump can cost $400 to $1600. These units usually include controls to regulate temperature and humidity in the home. When purchasing a heat pump, be sure to compare brands, price and value. Look for certification seals such as UL (Underwriter Laboratories) and ARI (Air Conditioning and Refrigeration Institute). Look for units with high SEERs and COPs or HSPFs (heating seasonal performance factor).

II. Residential Energy Use Page 12 The higher the SEER and COP, the greater the cooling and heating efficiency of the unit. Look for service and warranty agreements. The warranty usually guarantees the unit for one year and the compressor for five years. Make sure you understand the warranty. Regardless of your personal decision always consult a knowledgeable dealer or engineer who can recommend the best system for your situation. Ventilation Proper use of ventilation can reduce cooling loads, and prevent moisture build-ups in the attic. A system that moves at least 1 1/2 cubic feet of air per square foot of ceiling area reduces air conditioning costs. However, the cost is not reduced significantly in a well-insulated house. Soffit, roof gable, and ridge attic vents can reduce summer heat gain by moving heated air from beneath the roof to the building s exterior. Use one sq. ft. of ventilation for every 300 sq. ft. of insulated area with a vapor barrier, and one sq. ft. of vent for every 150 sq. ft. of insulated area without a vapor barrier. Window and ceiling fans may be used instead of air conditioning to achieve comfort during the periods of March to May and September to November. Ceiling fans are also helpful as air circulators when the air conditioning is on. A roof air recirculator reduces thermal stratification and decreases heating loads. Vertical temperature differences of 15 degrees F (8 degrees C) in rooms with eight-foot ceilings are not uncommon. An air recirculator can be fabricated with a four-inch diameter tube extending to within six inches of the ceiling. The tube is placed on top of a squirrel cage fan in a box on the floor. Air is drawn from the ceiling and exhausted along the floor, resulting in a vertical temperature difference as low as 1 degree F. A blower should cycle room air ten times each hour. Moisture Control Moist air feels warmer than dry air of equal temperature. Air s capacity to hold water vapor increases with rising temperatures. Relative humidity is a measure of the air s percentage of saturation with water. As the temperature rises, the relative humidity for a given amount of water vapor in the atmosphere decreases. When moisture-bearing air is cooled, the dewpoint is reached and water droplets form as condensation. When 70 degrees F (21 degrees C), air at 20 percent relative-humidity in the home creeps out of the house and is exposed to 28 degrees F (-2 degrees C) outside air, the relative humidity becomes 100 percent and condensation occurs. A major symptom of a condensation problem is dry rot. Four conditions are necessary for this fungal growth: 1) absence of light, 2) wood substrate, 3) moisture, and 4) temperature in excess of 50 degrees F (10 degrees C). Condensation most often occurs on the inner surface of the outside boards of a house. Usually, uninsulated houses do not meet all four conditions for dry rot, and so dry rot is not a problem. The use of insulation increases the chance of moisture problems. The solution to this condensation problem is to keep the thermostat above the dew point temperature. Usually, 78 degrees F is sufficient in the summer. Additionally, indoor air moisture can be minimized by using bathroom exhaust vents when taking showers and baths, wiping down shower stalls, placing the towel outside to dry and moving indoor plants outside. Indoor moisture is not such a large problem in the winter, except on extremely cold days. Moisture problems can be minimized with an infiltration wrap placed on the outside of the house. Vapor problems are not recommended for Florida because placement for both summer and winter effectiveness can be problematic. Tightening the inside surface against seepage of warm house air through the wall insures that outside air fills the wall air space. A vapor barrier is used to accomplish this end. It is typically made either of six millimeter polyethylene or one millimeter aluminum foil. Care must be taken to seal around electrical outlet holes and window frames so that infiltration does not decrease the benefits of vapor barriers. Loosening the outside, so that it breathes vapor yet sheds winds, is a means of decreasing vapor problems. Use of vents or shingle siding is helpful. Outside walls of plywood may be too airtight, and vent holes may be necessary. Moisture problems are also common in attics, especially in North Florida. Roofing materials themselves are excellent vapor barriers, so the ceiling needs a vapor barrier inside the insulation to trap moisture in the living space. Ventilation is important to counteract attic moisture (and heat) problems. Louvered and screened attic soffit and ridge vents should have an area of one square foot for every 150 square feet of ceiling area for a ceiling without a vapor barrier, and one