At the Austin experimental development, where the average cost of cooling a house through five summer months was $109, one airconditioning unit did the job for only $57 while another unit, in a neighboring house of similar size, struggled and gurgled through the summer at a cost of $172. Why this difference?
The engineers had to take many factors into consideration. Some families did considerable baking and roasting in their ovens. Some sat long hours before television sets that radiate British Thermal Units (a measurement of heat) by the hundreds. Some have children who untiringly pop in and out of doors, with resultant loss of cool air. But despite all this the engineers were able to connect cost of cooling with good and bad construction planning. For the prospective home owner the engineers listed in order of importance 15 suggestions for the efficient operation of a cooling unit:
1 No hot sun should strike window glass. Houses with the lowest cooling cost generally had shading devices over the windows. A picture window that caught the afternoon sun boosted cooling expense on one house by 15%.
2 A house should be well insulated against both heat and moisture. The attic floor should have the equivalent of six inches of rock wool and the walls four inches. Floors, walls and ceilings should have moistureproof vapor barriers.
3 Ventilation between the roof and ceiling should be adequate. In summer attic temperatures often reach 150° if the air is imprisoned. Much of this heat radiates into the house.
4 The size of a cooling unit should be determined by an expert's careful analysis. A unit that is too small will not do the job and one that is too big will result in poor humidity control.
5 The house should have a light-colored exterior and roof. Bright surfaces tend to reflect heat. Dark surfaces absorb it.
6 Family living habits should be arranged to help the cooling unit. Humidity and temperature control is upset by the housewifely compulsion to turn the cooler off at night. A kitchen exhaust fan should be used freely when cooking is in progress. Children should be taught to close doors quickly.
7 Clothes driers should be vented to the outdoors. A drier releases enormous amounts of heat and humidity.
8 The air-conditioning system should be installed by an expert.
9 The air in the house should move constantly. The blower in a cooling unit should not be run intermittently. Also the unit should be set to bring in some fresh air from out of doors.
10 Ducts that carry air from a central unit should be installed wherever they pass through uncooled spaces. In one house cool air flowing through an uninsulated attic duct picked up 27° of attic heat before it reached the rooms.
11 The register openings through which air enters should be situated near the outside walls of each room.
12 The air conditioner should be so constructed that no water stays on the cooling coils when the machine stops, or so that the air by-passes the coil completely. Otherwise excess humidity results.
13 The air conditioner should be built with good insulation and a tight seal between it and whatever heating equipment it adjoins. Any cold air leaking into most heaters will cause condensation of water, with rust and corrosion resulting.
14 The air-conditioning unit should be built so that the homeowner can do some of the servicing, like oiling the fan and changing the filter,
15 Little space need be sacrificed to the machine. Plenty of neatly cased central units now on the market take up less than nine square feet of floor space.
The noise that some Austin families found objectionable was checked by engineers with sound meters. At various times 19 of the test machines exceeded the FHA's allowable limit of 40 decibels. In rooms situated near compressor units, readings as high as 54 decibels were noted-higher than the noise level in an average office. Because some machines were situated with condenser coils and compressors out of doors, a few families found their neighbors' machines more offensive than their own. The noise was a result partly of faulty installation and partly of bad equipment design. The engineers recommend that wooden platforms built for mounting the equipment be properly isolated from the framing of the house, and they also have stimulated manufacturers to line the cases of the units with sounddeadening insulation.
With final engineering analyses still to be published, the test families are already on record as in favor of their new way of life. Even families with the highest bills are delighted and consider the cost small enough to escape the heat. And families with efficient cooling systems have discovered an extra bonanza: good insulation makes possible a substantial saving in winter fuel bills.
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