Whole House Fans Have a Lot to Offer

Photo: Giles Douglas/flickrWhole house fans have changed -- for the better! Although this natural home cooling method has been around close to a century, it's begun gaining in popularity in recent years. Today's whole house fans are much quieter than they used to be. In addition, they are more energy efficient than standard air conditioning, important news as electricity prices rise. The cost to run a whole house fan is only 1-5 cents per hour, compared to 15-20 cents for central air. Now that's cool!

How Whole House Fans Work

A whole house fan works to cool your home by circulating air. The system pulls fresh outdoor air into your rooms through open windows and possibly door, moves it through the house, and vents it out via your attic and roof. Especially in very hot climates, it is often used in conjunction with a standard air conditioning system (the two should not be operated at the same time, though, because the fan system would work to channel the air-conditioned air out of your home). You'll get the best and most effective cooling if you use the fan when the outside temperature is lower than the inside one, or less than 85 degrees F -- at night, in the early morning, and on milder days -- and your a/c when the reverse is true.

Whole house fan size is described in terms of cubic feet per minute (CFM) of cooling power. Determine the size that's right for your residence based on:

a) cubic footage of the part of your home you'd like to cool (area in square feet X room height)

b) number of air changes desired per hour (30-60, according to your climate and floor plan, as well as whether you plan to use the fan as your only method of cooling).

Multiply a) by b), and then divide by 60 to get the desired CFM.

Whole House Fan Installation

Whole house fans are usually installed in the attic -- typically the hottest part of the house, occasionally reaching temperatures of 150 degrees F. The fans can lower the indoor temperature of the attic by up to 30-50 degrees F. They are generally positioned on top of the floor joists.

It is vitally important to prepare your home properly before you install a whole house fan. Adequate ventilation is a must, both to ensure proper air exhaustion and to avoid any danger that the fan will circulate hazardous gases such as carbon monoxide, which are produced as byproducts of gas- or oil-combustion powered home appliances like a furnace or water heater. Attic vent area should be increased by 200-400 percent.

Install louvers which will alternately allow the air to circulate and close when the system is not in use. To prevent heat loss, the louvers should be covered in winter

A remote or hardwired timer switch should be part of the installation, as an easy way to get the most out of your system.

Whole house fan installation cost is about $450-650. Compare this with the approximate $2000-3000 price tag for central air conditioning.

Troubleshoot Potential Problems

The suction effect of a whole house fan is very powerful, especially when it is concentrated in one area of your home. To offset this, windows should be opened throughout your home while the fan is operating.

Noise can still be an issue, even with modern whole house fans. Installation by a qualified professional will alleviate this problem.

On days when the outdoor air quality is poor, due to high levels of pollen, pollution, or dust, operating the whole house fan might exacerbate allergy symptoms. At such times, it may be more advisable to cool the home with the a/c system.

A whole house fan does not help to dehumidify the interior air. In exceptionally humid weather, once again, you may choose to run your air conditioning instead.  

Laura Firszt writes for networx.com.

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