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How Does A Whole House Fan Work?

A Whole House Fan is one the Best Energy-Saving Solutions for Your Home

A Whole House Fan (also known as a whole house ventilation system, whole house attic fan or  whole house exhaust fan) is a simple & inexpensive method for cooling a home anytime the outdoor air temperature is cooler than inside your home.

How A Whole House Fan Works:

The diagram below illustrates how a Whole House Fan can provide effective natural cooling for a fraction of the energy cost of air conditioning by drawing cool fresh air in through open windows and purging hot stale air out through roof vents.

A diagram showing how Whole House fans expel hot air through the attic while pulling cooler air into living areas through windows.

As the temperature outside increases throughout the day, the heat gets captured in the walls and interior spaces of your home; this makes cooling exceptionally hard and expensive. When the outside temperature finally starts to cool, the heat that’s trapped in your house can often make the home uncomfortably hot – especially in second story of the home! Air conditioning, of course, is the typical solution for this problem; however, air conditioning during the hot summer months is very costly. A whole house fan provides you with a great, cost alternative to this problem! Due to its effective energy efficiency, a whole house ventilation system brings down the temperature of your home to a level that significantly reduces and in some cases eliminates the need for air conditioning. It also uses just a fraction of the electricity of a typical home air conditioning system.

Whole house exhaust fan limitations

Comfort Cool Fans unique design eliminates many traditional limitations with older style whole house exhaust fans. Problems with heat loss; loud intrusive operation and maintenance concerns are all solved. However, anyone considering a whole house ventilation system should understand that they do have limitations.

  1. A whole house fan is NOT the same as an air conditioner. Most air conditioning systems are designed to produce air that is about 20 degrees colder than the ambient temperature inside the home. For example, if the temperature inside the home is 80 degrees, the A/C unit will produce 60 degree air which in turn will cool the home about 1 to 2 degrees every hour.  Unlike an air conditioner, a whole house fan uses the outside air to cool the home but due to the large amount of air that it moves a 10-degree difference between inside/outside temperature is sufficient to start cooling the home.
  2. Removes heat build up from the entire building structure. During a hot day the outside of the house (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 during the 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 much quicker than newer homes. Although you may wake up to a home that is cool and comfortable after running your whole house fan the night before, you may find that your home quickly heats up as the temperatures outside rise during the day. This is due to the homes construction, not the whole house fan. Older homes typically consist of single pain windows and have less insulation in the walls and ceilings than newer homes. As a result, older homes allow outside heat to penetrative the home quicker than newer homes that have double or triple pain windows and have better insulation in the walls and ceilings.
  4. Multi-story home. A whole house fan draws more air through open windows downstairs even though the fan may be installed closer to the open windows upstairs. For this reason, if the main goal is to cool the upstairs bedrooms, then open the bedroom windows about 50% and close the windows downstairs. For bedrooms that are notably warmer than others, the windows should be open even more. Some experimenting is typically necessary to get the preferred result.