What is a Whole House Fan

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Video – How do whole house fans work?

A diagram of how a whole house fan works.
A whole house fan blows hot air out of your home through the attic and cool outdoor air is sucked in through the windows, making your home cool and comfortable. A whole house fan provides natural, effective cooling for a fraction of the cost of air conditioning, making it one of the best home energy efficiency upgrades.

How Homes Heat Up During the Day, and What to Do About It

As the outdoor temperature rises during the day, the heat is captured in the walls and interior spaces of your home, this makes cooling especially difficult and costly. When the temperature outside finally begins to cool, the heat trapped in your home during the day can often make the house uncomfortably warm – especially in second stories! Air conditioning, of course, is the normal solution to this problem, but air conditioning during the hot summer months is expensive.

A whole house fan provides you with a cost effective solution to your problem! Due to its great cooling efficiency, the whole house fan brings the temperature of your home down to a level that greatly reduces and in some cases eliminates the need for air conditioning. It also uses a fraction of the energy of a typical home air conditioning system making it one of the best home energy efficiency upgrades you can make.

Video: How a Whole House Exhaust Fan Works

Limitations of Whole House Exhaust Fans

The unique CentricAir design eliminates many traditional limitations with whole house fans. Problems with loud intrusive operation, heat loss and maintenance issues are all solved. However, anyone considering a Whole House Fan needs to understand that they do have inherent limitations as a cooling device.

  1. Whole house exhaust fans are NOT the same as air conditioners. Most air conditioners are designed to provide air that is about 20 degrees cooler than the temperature inside the home. For example, if the temperature inside the house is 82 degrees, the A/C unit will produce 62 degree air which in turn will cool the house about 1 to 2 degrees each hour. Unlike an air conditioner, whole house fans use the outside air to cool the house but due to the large amount of air that they move a 10-degree difference between the indoor and outdoor temperature is sufficient to begin cooling the house.
  2. Removes heat build up from the entire building structure. During a hot day the outside of the home (roof, walls, etc.) absorbs and retains a lot of heat. Until the heat dissipates, it will continue to radiate into the living space causing the air inside the house to heat up. By running your whole house fan in the early evening and at night, you are not only removing the hot stale air inside the home but you are also cooling the entire building structure.
  3. Older homes heat up quicker than newer homes. Although you may wake up in the morning to a house that is nice and cool after running your whole house fan all night, you may find that the house quickly heats up as the temperatures outside rise. This is due to the construction of the home and not the whole house fan. Older homes typically have single pain windows and less insulation in the walls and ceilings than newer homes. For this reason, older homes allow outside heat to penetrative the house much quicker than newer homes that have double pain windows and thicker insulation in the walls and ceilings.
  4. Two-story home. Whole house exhaust fans pull more air from open windows downstairs than open windows upstairs. For this reason, if the primary goal is to cool the upstairs rooms, then open these windows about fifty percent and close the windows downstairs. For rooms that are significantly hotter, the windows should be open even more. Some experimenting is usually necessary in order to get the desired result.