During the day, the air in your attic is heated. This attic air heats up the air inside your home. At night when the air outside cools down, a Whole House Fan can replace the warm air from your home with the cooler outside air. It does this by pulling in the cooler outside air through one or two open windows. The warm air is pulled out of your home and is pushed out of the attic vents. This cools your attic as well as your living area. This process will save you significantly on AC bills.