QuietCool QC CL-1500 Original Classic Fan Model The Quiet Cool Classic Line features our patented, selfcontained duct system that hangs in the attic to help neutralize the sound and noise vibration heard in the home. The included damper system features barometric pressurized gravity dampers that insure there will be no heat/cooling loss between the home and attic All Quiet Cool Classic Line fans include our standard efficiency permanent split capacitor motors. These motors offer aboveaverage efficiency with enormous value. 1472 CFM Covers up to 740 Square Feet