Whole House Fans

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Introduction

Whole-house fans typically use about one-tenth 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.

Technology Options

Attics can be brutally hot on a summer's day. When heat is absorbed by the walls and ceilings, attic temperatures can climb to over 150°F. Even if the ceilings are well insulated and the home is air conditioned, this heat can seep from the attic down into the home.

The whole-house fan pulls air in from open windows and releases it through the attic and roof. It provides good attic ventilation as well as whole-house ventilation. While whole-house fans may be placed in a number of locations, the most common 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 the attic.

Whole-house fans are designed to operate in the early morning and after sundown, when the outside temperature drops below 80°F. You can regulate cooling by simply closing windows in the unoccupied areas and opening windows wide in occupied areas.

Whole-house fans come in either belt-drive or direct-drive models. A direct-drive unit has the fan blades attached directly to the motor shaft, while belt-drive units have the fan blades attached to the motor shaft via a pulley and belt. The direct-drive unit is generally less expensive to buy, operates at a higher speed and requires less maintenance. However, it may be noisier.

Operation and Maintenance
  • Since whole-house fans will continue to draw air out of the house and replace it with outdoor air year-round, be sure to cover and insulate the fan during winter months.
  • Open windows, especially in the evening, to ensure adequate indoor air flow and to speed up the time needed to cool the home.

Efficiency Benefits

By using a whole-house fan to keep the home cool during the night and morning hours, you are decreasing the amount of time that the air conditioner needs to operate. Every hour that the fan is operated, you use one-tenth the electricity required to run the air conditioner. (A whole-house fan uses 120 to 600 Watts.) The savings can add up fast. For example, a central air conditioner can cost up to $250 to run per cooling season and a large window air conditioner can cost almost as much; a whole-house fan costs less than one-quarter the amount needed for air conditioning. (Operating costs are based on national averages. Your savings will depend on your local utility prices.)

In some climates, whole-house fans may eliminate the need for air conditioning altogether, especially during the spring and fall months.

Manufacturers

Tamarack, Grainger, and Garbeck Airflow LLC all manufacture whole-house fans of various sizes and models. Check your local hardware store or building supply center for other models.

Purchasing Tips

  • Evaluate the space. Whole-house fans should provide houses with 30 to 60 air changes per hour (varying with climate, floor plan, etc.). Check with a professional to determine what is appropriate for the home.
  • Include fan covers. The whole-house fan is essentially a large hole in the ceiling. To prevent heating and cooling loss through the fan when it is not in use, look for a fan cover or have one constructed to seal the fan when the air conditioner is in use and when the home is being heated in the winter.
  • Look for two speeds. A two-speed fan allows the home to be ventilated quickly on high speed and provides comfortable ventilation on low speed. Being able to adjust the fan depending on your need will help save even more money.
  • Evaluate noise. If installed correctly, a whole-house fan should not be very noisy.
  • Watch out for back drafting. Because of the decrease in pressure that a whole-house fan creates, combustion appliances that use indoor air for combustion can back-draft, creating a potentially hazardous situation. Ask the contractor to make sure that this will not happen.