Whole house fans provide cooling by exhausting hot air from the attic and living spaces. They are sometimes confused with attic fans. Attic fans can help keep a house cooler, but they only remove hot air from attics.
Whole house fans are installed in the ceiling, in a central location of a home (or sometimes in a wall, but rarely so). They are located in a place where air can blow into the attic. Whole house fan blades are large and provide significant ventilation pressure to cool a house. This type of fan can exchange the air in a 2400-square foot home within five minutes, allowing homeowners to turn off A/C at night. In areas of low humidity, whole home cooling fans can work without A/C, even on the hottest days, to make a home comfortable.
Attic roof fans are smaller than whole house fans. They are designed to move air out of an attic only. They help cool a home by venting hot air from an attic space and take a considerable load off of A/C by keeping ceilings cooler. Both attic and whole house fans need to exhaust and take in air to work.
Be sure to install enough intake vents in the roof to avoid drawing air from inside the house, rather than from outdoors. Drawing air from indoors can overload an A/C unit and send energy costs sky high. Similarly, with whole house fans, installing enough exhaust vents through the roof is essential for efficient circulation. Failure to do so will keep fan blades from moving enough air.