Your entire house is then cooled by outside air, without the needed help of your air conditioner. Because whole-house fans use far less energy than air conditioners, they cut cooling costs. While whole-house fans may be placed in a number of locations, the most frequently used spot is the hallway ceiling. Louvers normally close off the fan when not in use so that conditioned air doesn't escape through it. When the fan is operating, these louvers open, allowing air to be blown into your attic.
Attics can be brutally hot on a summer's day.
When heat is absorbed by your walls and ceilings, attic temperatures can climb to over 150 degrees. Even if your ceilings are well insulated and your home is air conditioned, this heat can seep from your attic down into your home. A whole-house fan, however, draws cooler outside air through your open windows and forces it through the attic and out through the roof vents. Your house and your attic are all cooled. Whole-house fans are very powerful and need sufficient attic ventilation to be effective.