Whole-house fans are large ventilation fans, typically installed in the attic, able to cool an entire house at a fraction of the cost of air conditioners. Like window fans, they are operated during the coolest part of the day (typically during the nighttime period, late evening and early morning), when outside temperatures are lower.
A Low-Cost Alternative to Air Conditioners
While central air conditioners cost thousands of dollars, typical whole-house fans cost a few hundred dollars. And their running costs are estimated at about 1/10 of the costs of AC.
That makes whole-house fans a low-cost alternative to air conditioners, in hot climates with cool nights.
Whole-house fans are ineffective during the hotter parts of the day when outdoor temperatures are high. They mostly provide nighttime cooling, which may be enough to let the house coal through the hottest hours of the day.
How They Work?
Typical whole-house fans draw fresh air in through open windows and exhaust the inside air into the attic, but there are also ducted models, designed to exhaust air directly out through the roof or a side wall.You just have to select the rooms you want to cool with the whole-house fan, by opening the windows where you want to draw outside air in, and by closing them in rooms that you don't want to cool.
Whole-House Fans in Hot Dry and Humid Climates
Whole-house fans are most effective in hot climates with cool evenings and nights.
They are not advantageous in areas with high humidity; in these areas, you will have to wait until outdoor temperatures drop below 70ºF/21ºC before using the fan.
Buying a Whole-House Fan
New whole-house fans are better sealed and have better blades than traditional models, but contrary to the claims of manufacturers they aren't necessarily more energy-efficient.
According to the EPA/Energy Star program all whole-house fans “perform about the same”… Modern whole house-fans may not justify their much higher prices.
See: Whole-House Fans: New vs. Traditional Units
Whole-house fans vs. Attic-fans
Whole-house fans are often called attic-fans. But they are a different type of fan. True attic fans are designed to cool the attic, while whole-fans are intended to cool the living space.
Size & Performance
Some whole-house fans are able to move 12.000 cubic feet of air per minute (CFM). But average sized homes with reasonable levels of insulation and shade will not need such powerful fans. 1.000-4.000 CFM units are often sufficient enough or average homes.
Noise & Installation
Whole-house fans can be noisy. To minimize the problem you should install the fan on rubber or felt gaskets, and look for a quieter model.
Pay also attention to the attic ventilation. Typical whole-house fans exhaust inside air out into the attic, which may require the installation of additional attic vents.
Our Video on Whole-House Fans And Window Fans: