Attic fans are used during the heat of the day to remove superheated air from the attic by drawing cool air in from outside through the vents and pushing the hot air to the outside through the attic fan itself. Attic fans do not cool the house (like a whole house fan does), but help keep the house cooler by lowering the amount of heat coming from the attic through the ceiling. To be effective, an attic fan must be combined with adequate, unblocked attic vents and an attic that is well sealed from the rest of the house. Both wired and solar-powered attic fans are available and an automatic thermostat/timer is recommended (set to turn on when attic temperatures reach a certain maximum), especially with a wired fan, so the fan only operates on the hotter summer days when needed. See the Energy Star website for more detailed information.
For more information about how much money and energy this product could save you, please see the U.S. Department of Energy, Home Energy Saver .