Technical News
What do buyers want from air conditioning?
Cooler temperatures, a constant flow of air and they don't mind a lot of noise; says final A-C Village report
People who live in1 air-conditioned houses talk about cooling from experience, rather than theory.
What some of them have to say forms the basis of the latest and final report from nahb's Air-Conditioned Village in Austin, Tex., and flatly contradicts three wide-spread theories about home air conditioning:
• "Houses need be only 10°-15° cooler inside than out." Not so says the report: buyers want houses that are several degrees cooler in summer than the 80° temperatures builders commonly guarantee, regardless of what the outside temperature is.
• "Keep the humidity as low as possible." Good, but not essential. Relative humidity is not as important as continuous air circulation.
• "People demand almost silent equipment." No they don't. Noisy units almost never seem bothersome.
Here are the details from the nahb report:
How cool should a house be? The occupants of the 22 test houses in Austin rebelled against an 80° indoor summer temperature. They wanted their houses at least as cool as 77°. Some owners wanted a 70° temperature before they were satisfied.
This new temperature specification on the part of homeowners just confirms other research which shows that home cooling systems should be designed to maintain 75° indoors.
At the Austin houses tests were made when outside temperatures stood at 95° and again at a torrid 105°. It is a popular belief than an air-conditioned house need be only "10° to 15° cooler inside than out" but Austin researchers found: "no difference in indoor comfort under these conditions," which confirms the fact that temperature difference between inside and outside has little bearing on human comfort.
How important is humidity control? The
report suggests that humidity, per se, is not so important as it was thought to be. Under various conditions, the test house occupants accepted a wide range in relative humidity from 30% to 70% RH. There were no discomfort complaints, provided the temperature at the same time did not exceed 77° and also provided there was a constant flow of air inside the house.
Keeping the house air moving is seemingly more important than maintaining
low humidity, the tests show. When the indoor air was in motion no families reported discomfort. But when the blower was shut off, stopping air circulation, complaints began to spiral, even though the indoor temperature and humidity were exactly the same as before.
This clearly indicates that home coolers should be adjusted for continuous air circulation. Many systems today are hooked up so that the air blower automatically shuts off when the thermostat is satisfied. The report advises builders not to set their systems up this way.
What about noise? The tests do not clearly define the level of equipment noise that owners will accept before complaining, but evidently they can stand more noise than the commonly accepted 40 decibel limit. (FHA's current MPR sets a 45 decibel limit.)
"Only two of the 22 families reported discomfort due to noise," the report says, "even though equipment noise in most houses exceeded 40 decibels." The report did find that "the reduction of sound from outdoors due to closed windows made a significant contribution to indoor comfort."
The report also says that:
• Final cost figures show the test houses were heated and cooled last year at an average total cost of $116 per house, or less than $10 per month. This figure is based on Austin utility rates, breaks down to $90 for annual electricity (including winter fan operation), $23 for gas heat, $3 for summer cooling water.
• Biggest service problem was dirty air filters. The owners habitually forget to clean or change the filters periodically.
• Lack of adequate space for the air conditioner "can increase a builder's installation cost far more than the cost of space needed." Builders are cautioned to allow enough space around the unit for side and back connections, makers are also urged to turn out units that can be fully hooked up from the front.
• Location of air outlets has a sharp effect on cooling comfort. Best results were in houses with perimeter floor outlets (unobstructed by furniture) and ceiling diffusers. Worst results occurred when perimeter outlets were obstructed. Intermediate results were recorded, in order of decreasing efficiency, for outlets located low in outside walls, high on inside walls and in baseboards.
The report also includes information on equipment sizing and house design. Copies are available at $2 apiece from nahb Research Institute, 1625 L St., N.W., Washington 25, D.C.
What's new in research?
Top housing research organizations announce some recent developments
Building Research Advisory Board (brab) last month finished a report on "The Anchorage of Exterior Frame Walls to Various Types of Foundations." It contains a simplified formula to guide builders and architects in determining if exterior wall anchorage is needed in a particular house.
Made at FHA's request, the study costs $1.50 from BRAB, 2101 Constitution Ave., Washington 25, D.C.
National Bureau of Standards. Here, an exhaustive study of asphalt roof shingles is in process. An interim report: "Durability of Asphalts Containing Mineral Additives," was released last month. It says that "additives such as mica, blue-black slate and oyster shell can significantly prolong the service life of roofing grade asphalt."
bms report 147 is available from Superintendent of Documents, Government Printing Office, Washington 25, D.C.
Lumber Dealers Research Council (Lu-Re-Co) reports on a new Lu-Re-Co floor panel developed by the Small Homes Council. Panels are made on the same jig used for Lu-Re-Co wall panels and can be easily varied in size to fit flooring requirements.
Detailed booklet costs $1 from Lumber Dealrs Research Council, Suite 302, Ring Bldg., 18th & M Sts., Washington 6, D.C.
National Sanitation Foundation study shows that you can use plastic pipe with perfect safety to transmit drinking water underground.
Results of a four-year investigation indicate that plastic pipe has no effect on the purity, taste or odor of the water, nor is there any difficulty in maintaining chlorine residuals.
Based on the study, plastic pipe makers have created a hallmark to identify the plastic pipes that are suitable for transmitting drinking water, so that you can identify on sight the kind of pipe you want.
The study was carried out at the School of Public Health, University of Michigan, and was financed largely by a grant from I the Society of the Plastics Industry (SPI).