Whole-house fan an economical tool for keeping cool


July 17, 1993|By Gene Austin | Gene Austin,Knight-Ridder News Service

Homeowners who want to cut cooling expenses can often get good results with whole-house fans.

In climates such as the Northeast's, where many nights are cool, a whole-house fan can keep some homes comfortable except in the hottest weather. In general, the fans work best in smaller houses.

A whole-house fan gets its name from its ability to move air through an entire house. It is actually a large, high-powered exhaust fan that pulls cool air into a house through partially open windows. At the same time it is pulling in cool air, the fan expels warm inside air from the house.

Even though whole-house fans have relatively large motors, they can be operated much more economically than air conditioners.

Whole-house fans are sometimes called attic fans because they are generally installed in attics. A fan installed in an attic pulls air through an opening in the ceiling below it and expels air through vents in the attic.

Whole-house fans can be installed in other locations, including walls and rooftops, if equipped with safety grilles and given protection from the weather.

Some whole-house fans are also designed for installation in windows. This is a good choice for a row house or other houses without an attic.

Whole-house fans designed for attic installation generally have a blade diameter of 24 inches or more. Whole-house fans for window mounting usually have 18-inch or 20-inch blades.

The power of whole-house fans is measured by the amount of air it can move. This rating is expressed in CFM or cubic feet per minute and ranges from about 3,000 CFM for smaller fans to more than 12,000 CFM.

Ideally, the fan should be sized to change the air in the house once each minute. For example, if a house has 1,200 square feet of living space and the rooms have eight-foot ceilings, there is total air volume of 9,600 cubic feet (1,200 multiplied by 8) and the fan should have a CFM rating of at least 9,600.

Prices for whole-house fans start about $120. They are sold at many home centers. Many fans have variable speeds and can be equipped with thermostats and/or timers to give better control of temperatures in a house.

Installing a whole-house fan in an attic requires cutting a square opening in the ceiling plaster or drywall under the fan. Generally, it is not necessary to cut ceiling joists.

A hallway or central point in the house is the best location for the ceiling opening, which is fitted with a shutter-type cover that opens automatically when the fan is in operation.

Most fans come with installation instructions, some showing alternatives to ceiling installation, such as mounting in an attic gable or wall. Do-it-yourselfers not familiar with electrical work should hire an electrician to wire fans.

Exhaust-vent area is an important consideration when installing a fan. In many attic installations, vent space must be increased. Fan instructions specify the amount of vent area needed, and these instructions should be followed carefully. Usually, one of the simplest ways to increase vent space is to enlarge the attic gable vents.

Getting good results from a whole-house fan usually requires some testing. Most fan owners run their fans in the evening and at night when the air is coolest. Windows in various areas of the house are generally opened a few inches. Interior doors must also be kept open to allow air to circulate freely.

The fan is shut off in the morning and the windows closed to contain the cool air. Draperies on sunny sides of the house are often kept closed. When the house starts warming up, windows are opened and the fan is put back in action.

In very hot weather, when the temperature at night is warmer than about 70 degrees, a whole-house fan generally will not make a house comfortable. A homeowner with central air conditioning can run the air conditioner at these times, or a couple of strategically placed room air conditioners can serve for these periods.

If a house has both a whole-house fan and air conditioning, don't run the fan while air conditioners are operating, since the fan will exhaust expensively cooled air.

Q: We put a sealer on our flagstone patio to give it a shine, but the sealer is peeling and cracking. Is there a way to remove the sealer and restore the original appearance of the flagstones?

A: A paint stripper should remove the sealer. I'd try one of the new "safe" strippers, which contain fewer dangerous chemicals than conventional strippers. An example is 3M's Safest Stripper. Follow the instructions on the stripper container carefully.

Readers' questions and comments should be sent to Gene Austin, c/o The Baltimore Sun, Box 8263, Philadelphia, Pa. 19101.

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