| Home | Insulation | Conserving Energy Heating | Books | Links |
|
.
Exploring Your Options for Energy Savings Reduced to its simplest economic terms, the energy you use to run household appliances and to maintain a comfort climate in your home is a commodity. Whether it comes in the form of gallons of fuel oil, kilowatt-hours of electricity or cubic feet of gas, you buy energy from a utility or fuel company—and probably pay a lot for it. There are two basic ways to reduce the amount of energy you buy. The first is to employ conservation measures. The second is to harness an alternative source. To discover the ways you can best approach these goals, take stock of your needs and the potential of the resources available. For example, if you have a large family and spend a high percentage of your energy dollars on hot water, your highest priority may be finding a way to save on water heating. If you live in the sunny Southwest, a solar water heating system could cut your fuel bills dramatically; if your home is in a cloudier climate, a heat-pump water heater might be a more practical solution. The first step in making such decisions is to conduct an energy audit of your house. Begin by analyzing your fuel and utility bills, as explained in the box opposite, to determine how much energy you are using and what you are using it for. Most consumers spend more than half their energy dollars heating or cooling their homes. Many are paying in large part for wasted energy—wintertime heat that escapes through poorly insulated walls and out cracks around doors and windows, or summertime air conditioning that compensates for outside heat creeping in via the same pathways. To determine whether your heating or cooling bills are excessive for your area, give your house an efficiency rating by means of the formula outlined in the box. To do the arithmetic, you will need to convert your present heating energy requirements into BTUs and to find out your area’s annual number of heating- degree days (HDDs)—a measurement used by weather experts to define the severity of a given climate. A BTU—for British Thermal Unit—is a standard measurement of heat energy. One BTU is the amount of heat needed to raise the temperature of 1 pound of water 1° F. A gallon of fuel oil produces 140,000 BTUs; a kilowatt-hour of electricity 3,400 BTUs; and 100 cubic feet (1 CCF or therm) of gas 100,000 BTUs. Heating-degree days are calculated by subtracting the average temperature for each day from a base temperature of 65°. For example, a day with an average temperature of 31° is rated at 34 HDDs. Annual HDD totals range from 1,500 in regions along the Gulf of Mexico to 10,000 along the U.S.-Canadian border. To find the HDD figure for your area, ask your local utility company. Many utilities also calculate cooling-degree days (CDD5), the difference between 65° and the average outdoor temperature. Annual CDD totals range from approximately 200 in the Northwest to more than 3,000 in the Southwest. The result of your efficiency calculations will be the number of BTUs your house consumes, per square foot, per heating- or cooling-degree day, in order to maintain a comfortable temperature. If you come up with a poor to average rating, examine the house to see how energy is going to waste. Although you can do this on your own, you may want to get advice from your local utility company or an energy audit firm. To help consumers find ways to con serve energy, federal law requires utilities either to perform walk-through house inspections for a minimal fee or to provide explanatory literature that will enable homeowners to conduct inspections. You or the utility auditor should check the condition of the caulking and weather stripping around doors and windows, examine the heating and cooling systems to see if they are at peak efficiency, and rate the insulating ability of your walls, roof and windows in terms of R value. R value is a measurement of a building material’s ability to slow the passage of heat: the higher the R value, the more effective the insulation. The wall insulation in most well-built contemporary homes ranges from R-11 to R-19 and ceiling insulation from R-19 to R-38, depending on the climate. If your house is inadequately insulated for your area, your utility company can advise you on how much additional insulation you will need in order to bring it up to standard. If the results of your energy audit indicate that your home is operating at peak efficiency, you can start to consider some of the modifications—or retrofits, as they are called—described on the following pages. The effectiveness and practical value of any energy retrofit depends on a combination of several—in some cases, all—of the following factors. CLIMATE. The climate of a region, as rated in heating- or cooling-degree days, gives an indication of how practical certain conservation measures might be. For example, a house located in an area with a high number of heating-degree days will save money with super weather- proofing measures such as triple-glazed windows (18) or extra-thick insulation (26-31). Homes in warmer climates—with a high number of cooling- degree days—will benefit more from a ventilating system, such as the solar chimney (10-15), that will cut the load on an air conditioner. The direction of prevailing winter winds in your region may tell you which walls need insulation or which windows need extra glazing. Your weather bureau can provide data on wind direction. HOUSE SIZE AND SHAPE. The total square footage of a house—or a room— often dictates the size of equipment such as solar collectors. The dimensions and shapes of outside walls determine where (or if) you can mount certain solar de vices such as thermosiphoning air panels (48-57). To take the measurements, sketch rough floor plans of the rooms, draw elevations of exterior walls, and note down all the dimensions. SOLAR ORIENTATION. In the Northern Hemisphere, the sun moves across the southern sky. During winter it moves in a much lower arc than in summer, so sun light striking the south wall of a house in December may be blocked by roof eaves in July. To get the full benefit of its warming rays, solar collecting devices must be mounted to face within 20° of true south—the more directly, the better. The sun lies true south at noon. True south, also called due south, differs from the magnetic south shown on compasses because of an anomaly that is known as the magnetic deviation. The discrepancy between true and magnetic south varies from one area to another, but any local land surveyor can tell you what it’s at your site. To locate true south on your own property, either check a survey map for your house lot or take a compass reading to find magnetic south, then compensate by the amount of the magnetic deviation in your locale. LATITUDE. The distance of an area from the equator is expressed in degrees of latitude—a figure available in any atlas. To catch noon sunlight face-on, solar collectors are usually mounted tilting at an angle equal to or within 100 of the latitude in which they are located. INSOLATION. Insolation is the amount of sunlight your area receives. It’s ex pressed in terms of BTUs per square foot or in langleys. A langley equals 3.69 BTUs. Insolation is a critical factor in calculating the potential output of solar devices and, along with the dimensions of the house, is one of the statistics used in determining how many square feet of collector surface you need. High rates of insolation will also indicate the need for heavy summertime window shading. Some utility companies and weather services re cord local insolation data. If you cannot get the information, write or call the National Climatic Center, Federal Building, Asheville, North Carolina, 28801. POTENTIAL OUTPUT. Some energy de vices, such as heat pumps and wood furnaces, are rated according to how many BTUs per hour they are capable of producing—information that the manufacturer or dealer can furnish. To estimate how well a proposed installation will handle your needs, weigh its BTU output against your BTU requirements, as figured in the energy audit. Solar collectors are rated according to how many BTUs they can deliver per square foot of glazing area during daylight hours. A solar- equipment distributor may have performance statistics for sample climates to help you size your collector. COST EFFECTIVENESS. The cost effectiveness of a retrofit is calculated by making an estimate of its payback period—the time it will take for the installation to pay for itself. For example, a $600 heating de vice that can handle 10 per cent of a home’s space-heating needs will trim $100 a year from a $1,000 annual oil heating bill. It will pay back its costs in six years. (When figuring costs of a retrofit, check to see if it qualifies for tax credits, which will help defray its expense.) Not all retrofits can be counted on for quick payback periods. But favorable payback is only one reward for installing energy retrofits. An installation that results in noticeable savings can add to the resale value of the home. For many owners, there is a value that cannot be measured in dollars and cents: the personal satisfaction of conserving energy. Scrutinizing Your Costs Begin an energy audit by obtaining records of the monthly bills for the past three years from all the utility or fuel companies from whom you buy energy. The records should list the number of units of fuel charged to the house and the total price per billing period. Do all of the calculations in terms of units of fuel. You can later convert the figures to dollars by multiplying by the unit price. To find out how much energy your water heater uses, subtract the ground water temperature from the hot-water temperature. Multiply that figure times 20 (the gallons of hot water a typical person uses each day) and that by 8.33 (the number of pounds in a gallon). Then multiply the result by the number of people in your household and by 30 to get the total number of BTUs required for water heating each month. For gas or oil water heaters, factor in an efficiency rating by dividing the total by .75 if the heater is less than 10 years old or by .5 if it’s more than 10 years old. Convert the BTUs to units of fuel. To isolate air-conditioning and heating fuel consumption, first calculate your home’s base load—the more or less fixed monthly energy needs of lights, appliances and water heater. Then subtract the base load from a month’s total utility bill. To find the base load for an all- electric house without air conditioning, average the bills for June, July and Au gust by adding up the kilowatt-hours consumed and dividing by three. For an all-electric house that has air conditioning, determine the base load by finding two months in a year when the house was neither heated nor cooled; typically, electricity use is lowest during May and September. Average the kilowatt- hours used in these two months and subtract the result from your winter bills to isolate the heating needs. To determine a month’s air-conditioning costs, subtract the base load from a summer month’s electricity bill. For a house with an oil furnace and water heater, but electric appliances and air conditioning, average the summer oil bills to get the base load for oil and subtract the result from the winter bills to get heating consumption. To calculate air-conditioning needs, sub tract the average winter electricity use from the summer months’ bills. For a house that burns natural gas for heating, hot water and major appliances, average the summer months’ gas bills to find the base load for gas usage, and subtract it from the winter gas bills to isolate your heating needs. After you have figured the amount of fuel you use to heat or cool your house, determine whether your consumption is excessive. First, convert the units of fuel bought each month into BTUs: Multiply kilowatt-hours by 3,400; gallons of oil by 140,000; and therms or CCF (100 cubic feet) of gas by 100,000. Next, divide the BTU total by your local heating or cooling degree-day rating for that year. Convert this number to a square-footage basis by dividing it by the living area of your house, and you get a rating of the house’s heating or cooling efficiency. For heating, a rating up to 10 is excellent; from 11 to 20, average; more than 20, poor. For cooling, a rating up to 3 is excellent; 3 to 6, average; more than 6, poor. Thus, a 2,000-square-foot house that used 1,400 therms of gas per year with an HDD rating of 5,500 HDDs would be rated at 12.7, in the average range (1,400 100,000 = 140,000,000 ÷ 5,500 = 25,455 ÷ 2,000 = 12.7). |