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How Does A Whole House Exhaust Fan Work?

Updated on November 17, 2015

Today’s tightly sealed homes trap in hot, humid air, making us uncomfortable in our own homes unless we run our expensive-to-operate air conditioning systems.

Often, however, there’s cooler, drier air waiting just outside for those of us willing to install some kind of whole house exhaust fan to help us take advantage of it.

Generally, fans to pull hot stale air out of your home and replace it with cooler, fresher, less humid air fall into two categories: whole house attic fans and whole house window fans.

Attic Fans And Window Fans

Attic fans have the advantage of being able to cool an entire house with a single system, but they can be costly and complicated to install. Still, there are quiet, relatively simple-to-install alternatives like the Quiet Cool QC-4500 system, for example.

That system is nothing like the huge, noisy attic fans of decades past. In fact, attic fans have come a long way in recent years, so it’s worth exploring them again if you previously found the cost, noise or installation hassles of whole house attic fans difficult to overcome.

Whole house window fans take much less expertise to install, however, and can be removed easily if necessary. A high-quality whole house window fan like the Air King 9166 installs in minutes, costs much less than an attic fan and can clear a home of hot, stale air more quickly than smaller, less powerful window fans.

Window fans vary in blade size and capacity. Some are small in size but turn very fast, managing to move quite a lot of air even though they take up very little space. When window size allows, however, a larger fan makes more sense. A large fan has a greater capacity even when it turns slower. That’s important because the amount of noise a fan makes generally increases as the speed increases.

Even More About Whole House Exhaust Fans

The idea behind a whole house exhaust fan is simple: It pulls in cool air from outside and forces out -- or exhausts -- hot air from inside.

You may not need to run an air conditioner at all if you eliminate hot air with an exhaust fan, or you may at least be able to significantly reduce your air conditioning bill by exhausting hot air before running air conditioning.

Since whole house window fans work by exchanging hot, humid air inside a home for cooler, drier air outside a home, they have one limitation: They don’t work very well when the air outside a home is hot and humid.

That means they work best in mild climates and during seasons when there is cool air outside during the morning or evening of which you can take advantage.

Every home needs some way to exhaust the hot air the accumulates in it. While an air conditioning system can do this if you have one, there are more economical and efficient ways to do it.

Consider a whole house exhaust fan, and you could live in your home more comfortable for less money. Whether you choose a whole house window fan or an attic fan, you won’t regret your decision to clear out the hot air and bring in the cool.


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      win-winresources 5 years ago from Colorado


      Since you can't put air in without taking air out first, an exhaust fan is a great idea working just itself in blowing out hot, humid air and simultaneously drawing in cool air from outside (requires an open window on the shady side of the house). This can also be used as a cost-effective pre-exhaust prior to turning on the air conditioning.

      The most effective whole house exhaust fans are installed as attic fans for two big reasons. One, the higher up the wall (all the way to the ceiling), where the hotter air is caught and exhausted. Open windows are several feet lower, leaving hot air at head level. Two, the attic itself traps very hot air. The attic exhaust fan blows that out first.