Even if your home has air conditioning, consider installing a whole-house fan. Whole-house fans use far less energy than air conditioners and they cut cooling costs. In fact, whole-house fans typically use about one-tenth of the electricity of comparably sized air conditioners, and they are relatively inexpensive to install. Used correctly, they can help you cut your air conditioning bills substantially. Whole-house fans are designed to operate in the early morning and after sundown, when the outside temperature drops below 80 degrees. The idea is to turn off the air conditioning and to turn on the whole house fan. With your windows open, fresh, cool air is drawn into your home, forcing out the hot air. Your entire house is then cooled by outside air, without the needed help of your air conditioner. Remember not to run your air conditioner at the same time you use the whole house fan, and to keep most of your windows open when it's operating. Opening windows not only helps the air circulation, but it also prevents fumes or flames from your gas appliances and fireplace from being drawn back into your home. 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, however, these louvers open, allowing air to be blown into your attic. Attics can be brutally hot on a summer's day. When your walls and ceilings absorb heat, 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. Air conditioning alone doesn't offer that benefit. Whole-house fans are very powerful and need sufficient attic ventilation to be effective. Your contractor can help you determine the correct fan size, capacity and number of attic vents needed for your home.