Fans are one of the oldest and most reliable mechanical methods of cooling a home – and they use less energy than air conditioners.
However, fans don’t cool rooms in the same way air conditioners do by lowering the temperature. Instead, fans create a cooling effect by moving air across your skin.
A typical window fan uses 25% (or less) of the energy it takes to run a window-mounted air conditioning unit. So, you could conceivably run several fans and still use less energy than you would with a single air conditioner.
Window fans and whole-house fans are the best ways to accomplish power ventilation. Smaller floor, table and ceiling fans are best used to create a “wind-chill” effect indoors; they’re less effective as whole-house units.
A/C can be the answer
Opening the windows and using a fan during very hot and humid weather may not be a cost-effective cooling strategy if you use an air conditioner most of the time. Your air-conditioning costs actually could increase by as much as 20% because of the extra amount of moisture entering your home.
Out goes the bad air . . .
Whole-house fans can reduce indoor temperatures by up to 20°F, depending on the temperature outside. Installed in a hallway ceiling on the top floor of your home, a whole-house fan works by pulling the air from the entire house up into the attic, where it is vented to the outside. The resulting pressure difference causes fresh air to flow into your living areas through open windows. For efficiency, consider a variable-speed controller (to allow operation at different speeds, depending on the outdoor temperature) and a timer (to set the fan to turn off automatically). Remember, too, that to save energy in the winter, it may be necessary to seal off the fan.
. . . And in comes the good
On warm, still days, you can use a window fan to create cross-ventilation in your home. Open the windows on the shady side of your house and position your fan so it blows air out of a window on the hot side of the house. The resulting pressure difference will cause air from outside to flow through your home. While this option doesn’t work well on very hot and humid days, you might be surprised at how well it works the rest of the time.
Exhaust the possibilities
Kitchen exhaust fans mounted above ranges help remove heat and humidity created during cooking. Bathroom exhaust fans help remove the heat and humidity caused from baths and showers. Be sure to clean both types periodically. Also, don’t leave your exhaust fans on longer than necessary; in just an hour, one of these fans can blow a house full of cooled air outside.
Food odors and oven heat (and bathroom humidity) usually are gone within 15 minutes or less; a slightly opened window in the room can speed up this process.
Close, but not too close
Ceiling fans are probably the best way to circulate air in rooms, and they’re a great way to supplement your air-conditioning system. They have become very popular, with two-thirds of American households utilizing them for light and cooling. There should be at least seven feet between your fan and the floor for safety, but keep in mind that fans that are too close to the ceiling – advertised as “ceiling hugging” models – may not provide adequate flow. Ceiling fans should be installed at least 8 inches from the ceiling and 18 inches from walls. Blades that are too close to the wall or ceiling can be up to 40% less efficient.
A good ceiling fan should create enough air movement that you feel comfortable at 82°F and 80% relative humidity. If you’re using the fan to supplement or circulate air-conditioning, you should be able to raise the thermostat a full 4°F above the standard 78°F setting and still be comfortable. This is significant, because for every degree you raise your air-conditioner’s thermostat above 78°F, you save about 5% on your cooling costs.
Note: A caveat from Home Energy Magazine online: Ceiling fans can be big energy users, depending on how they are used and what kind of lights are used in conjunction with the fan kit. The lights often use more energy than the fan motors and, because they tend to be bright, may get used more than other, more energy-efficient lighting. Energy Star models are the best choice; most of the resulting energy savings will come in the lighting portion of the fan. Consider placing compact fluorescent lamps (CFLs) in your cailing fan lights.
Sizing a ceiling fan
Room Area (sq feet) - Fan Diameter (inches)
- Up to 75 square feet: 29-36 inches
- 75-144 square feet: 36-42 inches
- 144-225 square feet: 44 inches
- 375 square feet: 52 inches
- 225-400 square feet: 50-54 inches
To learn more about keeping your home cool this summer, check the Iowa Energy Center’s Home Series publication, Home Heating and Cooling.