Whole-house Fans: Easy, Low-cost Cooling

Enlarge Image Image Gallery Whole-house fans draw cool outside air into homes through open windows and out through the attic, cooling the entire house. ANIL RAO/RS MEANS

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Whole-house fans are high-capacity fans mounted in a central hallway in the first-floor ceilings of single-story homes and in the top-floor ceilings of multiple-story houses. They draw cool outside air into a home through open windows. The air flows through the house and is vented out through the attic. Whole-house fans bring huge quantities of cooler, nighttime air into a home.

Whole-house fans are used in a variety of climates — from moderate ones where cooling demands are low, to desert areas with hot days and cool nights. They’re even helpful in hot, humid climates such as the southeastern United States, where they can be used in the spring and early fall, when cooling demands are lower.

Whole-house fans are typically run early in the morning and in the evening, when outside temperatures fall below indoor temperatures. You can also use them to cool your home during the day if you have a cool, dry and non-musty basement. Warm outside air is drawn in through basement windows, then is cooled as it passes through this naturally cool underground space. The air then flows up the basement stairs into the main living areas and is vented through the attic. Be sure there are no toxic fumes or radon in the basement, and that it is free of mold; otherwise, this can be an unhealthy strategy. And you don’t want to leave windows open in areas at risk for break-ins.

Be sure to cover and seal your whole-house fan during cold weather. The louvered opening can be a major source of heat loss during the winter. Moist air could also escape into the attic and condense, causing moisture or mold problems, too. You can install the cover on the attic side, or on the ceiling in the living space. You also can buy or make a cover out of fiberglass duct board and duct tape.

Installing a whole-house fan is a difficult project involving electrical work and carpentry. If you tackle the job yourself, be sure to follow the manufacturer’s instructions. You’ll find installation guidelines in many home repair books as well.

Because whole-house fans operate only if windows are open, they should not be used at the same time as an air conditioner. But they are useful even if you do have an air conditioner. They provide a less expensive alternative early and late in the cooling season, or at night, if it’s cool enough. The air conditioner can be used if the fan is not running.

Before arranging to have a whole-house fan installed, check with your local building department to see whether a permit is needed. Also, check the type of wiring that’s required.

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