Hopefully we all agree by now that there is an immediate need for energy conservation. Convincing arguments can be made on economic, political, and environmental grounds for conservation. This article considers the economic basis since that’s what motivates most people.
Future articles will deal with the use of solar energy, the electric utility industry, and other subjects relating to energy supply and demand. The order of these topics is indicative of my general energy philosophy — be as energy efficient as possible, then worry about other energy sources.
This article is directed toward home owners, builders and renters. The numbers apply to retrofitting existing homes, but the ideas are valid for new homes as well. From an economic standpoint, I’ll try to answer the question of how much, what to do first, what combination of measures should be taken, how much will it cost, and how much will it save. That’s ambitious, so every energy-saving idea won’t be discussed. The basis for the numbers are prices and climatological data from the Research Triangle area.
To provide perspective on energy costs, consider that in Orange County, the cost of electricity and natural gas has nearly doubled in the past four years and that oil has increased even more. Despite that, the Southeast still enjoys very low energy prices compared to the rest of the country and the world. It looks like the price trends will continue, with oil and natural gas eventually exceeding the cost of electricity.
The average residence in Orange County spent $1200 or about 11% of the family income on direct energy expenses, in 1974-75. (From Energy in Orange County, available at the Little Professor Bookstore, Chapel Hill, 50 pg., $2.50) Of course, the energy costs inherent in goods and services greatly exceed direct expenditures but as yet there is no good way to measure these expenses. Some folks in all-electric homes are finding that their monthly utility bills can equal one-quarter to one-third of their mortgage payment. The logical conclusion is that homeowners and renters are (or should be) becoming much more aware of operating costs and are willing to make investments to lower these costs.
Energy conserving measures that can be taken are grouped below into five general categories. They are: insulating, weather-stripping, operation, external improvements, and purchasing.
One final word. Before you decide what is the best investment, you’ve got to determine your present energy costs. Considering that most furnaces are about 50% efficient, the actual cost of a unit of heat delivered into your home by burning oil or gas is twice the purchase price. Thus, at current prices, 100,000 BTU of heat will cost: oil 66¢, natural gas 45¢, electricity resistance 90¢, heat pump 45¢. The second concept to remember is that of marginal return. For example, the first six inches of insulation will save a lot more heat than the next six inches. In fact the second six inches may be a waste of money. That’s what energy consultants do — figure out what is the optimum investment.
If you’re still with me, let’s consider what the optimum levels of insulation are in the Triangle area at mid-1976 prices. Considering materials, labor, interest, and energy costs the best insulation levels are:
Electric Resistance Heat
attic — 12 in. batt or equiv.
wall — 3½ in. loose fill blown in.
floor over unheated area — 6 in. batt or equiv.
ducts in unheated space — 8 in. glass fiber duct wrap
storm windows or double glass
Oil Heat
attic — 12 in.
wall — 3½ in.
floor — 4 in.
ducts — 6 in.
storm windows or double glass
Natural Gas or Heat Pump
attic — 10 in.
wall — 3½ in.
floor — 4 in.
ducts — 5 in.
storm windows or double glass
The installed costs of these measures will be something like: attic, 6 in. batt, 20-30¢/sq. ft.; wall, 50-70¢/sq. ft.; floor, 6 in. batt, 25-30¢/sq. ft.; duct, 2 in. foil faced, 20-30¢/sq.ft.; and storm windows $25-30 each. All of these measures would pay for themselves in one to seven years. This analysis is based on a good, fairly technical publication — Retrofitting Existing Housing for Energy Conservation: An Economic Analysis, U.S. Government Printing Office, No. C13-29/2:64, $1.35.
Weather-Stripping
This is the most cost effective measure you can take, so do it first. Even renters who pay their own bills should consider it. The object is to reduce the seepage of cold air (infiltration) into your home. A tight house will leak enough (even due to a normal amount of door opening and closing) to displace all the air in the house every hour. If that seems like a lot of heating, it is! And that’s in a tight house. Some funky old houses can leak three times that much. Infiltration can account for one third or more of the total heating load. Weather-stripping can greatly reduce that loss. So I’m not even going to go through any economics on this one. It is the first thing to do.
Operation
What little data there are on energy use indicate that you can live in the best house in the world and still use a lot of energy. That is, energy consumption is very dependent on the habits of the occupants. Figure 16* shows the relative energy consumption and cost for various household operations. This should give you an idea of where to concentrate your efforts.
To reduce your heating bill, be sure that the fan motors are oiled, and the coils and filter are kept clean. Open your curtains during the day and close them at night. That way you can get a little solar heating. Along these lines, moveable polystyrene window panels can be purchased for about 20¢/sq. ft. If used nightly, even when placed over double pane windows, they will pay for themselves in less than two years. They can reduce your total heat loss by as much as 10% per year.
Since the rate of heat loss is proportional to the difference between the outside and inside temperatures, roughly every degree that the thermostat is set over 68° will increase the heating cost by 3%. So maintaining 71° would require nearly 10% more heat than maintaining 68°. This concept can be extrapolated to night-time setbacks. That is, if you keep the house at 68° for 16 hours and 60° for eight hours a savings of 8% will result, compared to maintaining 68° all the time.
For those people with air conditioning, the best advice is to use it as little as possible. This can be achieved without too much discomfort by closing the windows every morning and opening them every night. This cools the house each night (a fan may help) and allows you to “store the coolness” throughout most of the next day. Your polystyrene window panels will help in the summer too by blocking the direct sun. If possible, put them on the outside. The same idea of thermostat setting applies here as in heating. Every degree under 78° will require an extra 4 to 5% for air conditioning.
A lot of people are surprised by the amount of energy used by water heaters. The average family spends $140 per year on this item. Set the thermostats at 130° (most tanks have two, one at the top and one at the bottom) unless you find that you’re running out of hot water. Here, every degree over 130° costs an extra 3%. Wash clothes in warm water. They last longer and you save energy. Finally, use a solar clothes dryer (a clothesline). Water heating is a good application of solar energy. That will be discussed next month.
External Improvements
These improvements apply mainly to summer operation. If you don’t have air conditioning they’ll make your house a lot more comfortable. If you do, you’ll save money, too. Basically we’re talking about shading. The Alabama Forest Service did a study of air conditioning costs in mobile homes. They moved the homes around to vary the amount of tree shading. They found that a mobile home in full shade saved $45-100 per year in air conditioning costs. If this kind of shading isn’t possible now, plant some deciduous trees on the west, east and south sides of your house. While they’re growing buy some awnings to shade the windows.
A south-facing 3 x 5 ft. window will let in 9,000 BTU on a clear July day. That’s enough heat to raise the temperature of 10 gallons of water 100°. If you removed that heat with an air conditioner it would cost about $4 per year. A 42 x 39 inch metal awning costs about $20, so it would pay for itself in about five years.
Purchasing
Don’t forget that appliances take energy to make. So even though that electric can opener or toothbrush doesn’t use much energy to operate, it took a lot to build. That sort of thinking is the basis of a “net energy analysis.” At some time in the future maybe all items will be labeled with this information.
The journal Environment (vol. 14, No. 2, 1972) had a study of energy use in beverage bottling. It found that a 12 oz. bottle which cycles eight times (an average number) uses one third as much energy in the entire process — i.e. manufacture, transportation, cleaning, etc. — as a 12 oz. disposable bimetal can. The message is obvious.
Refrigeration / freezing is also a large energy user. Most new units come equipped with heating coils on the outside cover. This is done to keep the boxes from sweating in humid weather. These coils can add as much as 25% to the annual operating costs. This extra expense wasn’t necessary until the “bigger inside, smaller outside” (i.e. less insulation) units came out a few years back. So buy the old fashioned kind if possible. If not, be sure to get one that has a switch to control these coils. On some models its called a “power miser” switch.
If some, or all, of the measures that I’ve suggested here seem mundane, that’s because they are. However, they will save a lot of energy and until people do even these small things there’s not much use talking about life style changes, solar, wind, etc., it will all come in time. First plain economics will force it to happen, if we’re lucky enough to avoid a crisis in the meantime.
Next time we’ll try to rediscover techniques for using the sun that people knew about thousands of years ago, but forgot in the rush to burn up all of our fossil fuels.
*Figure 16: Average Orange County Residential Energy Use is available as a PDF only. Click here to download.
