The Cool Attic 30 in belt drive two-speed whole house fan is designed for houses with 2000 to 3000 sq-ft attics. It offers an efficient way to reduce cooling costs by pulling fresh air in from the outside, expelling the warm air up into the attic and pushing it out through your attic exhaust vents. This unit requires a minimum of 10 to 12 sq-ft of net free exhaust vent area to perform correctly. Dual, self-aligning ball bearing mechanisms and a precision-balanced four-blade aluminum fan assembly contribute to quiet, reliable performance and longevity.