What is a Whole House Fan?
A whole house fan is a large, powerful fan that pulls air throughout the entire house. These fans are usually 20 to 48 inches in diameter and are powered by an electric motor. Most often installed in the ceiling of the house's uppermost story, these fans exhaust air from the house into the attic, hence their alias, "attic fan." These fans are sometimes installed in upper story windows, or as a fan unit that is installed in the attic space.
How Does a Whole House Fan Work?
Whole house fans work by pulling cooler outdoor air into the house through open windows, replacing hot air inside the house. The breeze created by the fan gives the effect of cooler air throughout the house. As the fans work, they exhaust the hot air pulled from the house out through the attic, cooling the attic. Since hot air rises, the attic is often the hottest area of the house; an attic fan removes this hot air, reducing any heat gain from the hot air in the attic.
When a Whole House Fan Should Be Used
Whole house fans can "cool" the home only when the air outdoors is cooler than the air inside. Therefore, whole house fans are often used to cool houses in the evening, when the outdoor air has cooled. During the day, when the temperature outside rises higher than the temperature in the home, the fan is stopped and the windows are closed.
Is a Whole House Fan Right for Me?
The Iowa State University Extension says that "many people report considerable savings with a whole house fan, but say that they operate air conditioning two or three weeks per year during the hottest, muggiest weather." If you live in a humid area, you may need to operate an air conditioner or dehumidifier in addition to an air conditioner in order to remove moisture from the air. Additionally, if you suffer from dust, mold or other allergies, a whole house fan may not be for you, as fans will pull dust and other allergens into your home.