By Paul Bianchina
Q: We do not have an air conditioner, and I understand that whole house fans can be a good alternative for cooling. Is that true? Also, I've heard about power attic fans that get rid of hot attic air. Is this different from a whole house fan, and would it help? -Brian and Wendi C.
A: Whole house fans are mounted in the ceiling of the home, with a large fan located in the attic and a set of spring-loaded louvers that open to the living space below. When the fan is on, the louvers open and cooler outside air is drawn into the home through open windows, which pushes the warm air up into the attic and then outside through the existing attic vents (some additional attic venting may need to be added). Whole house fans can be a very effective method of cooling a house whenever the outside air temperature drops below the temperature inside the house, and, depending on where you live and the average summer temperatures, it can supplement or even replace the need for an air conditioner.
Powered attic fans are designed solely to remove hot air from the attic and exhaust it to the outside. They do not open into the living space of the house, so they provide no air movement in the house and don't draw any air from outside into the living areas. Lowering attic temperatures will help lower inside temperatures to some degree, and will also help prolong the life of your roofing. However, I have not seen any evidence to suggest that power attic fans do this substantially better than the natural attic ventilation that's achieved through the use of the passive high and low vents already in your attic. Also, passive vents operate for free, while powered attic fan utilize electricity.
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