Whole house fans are great for homes in parts of the country with low humidity. How do they work? Whole house fans suck in cool outside air and expel it into an attic (and then out via roof rents). Warm air in the house is replaced by cooler outside air.
Humidity is the key here—it must be low enough outside that when you bring that air inside, it doesn’t feel muggy. Basically, the western one-third of the US fits this bill.
Another key aspect of low humidity: once the sun goes down, dry air cools off quicker than humid air. That creates the temperature difference needed to make an attic fan work most effectively.
Here in Colorado, we’re experts in whole house fans. We grew up in houses with traditional whole house fans—often, this is all that was needed to cool a home at night.
This article focuses on three types of whole house fans:
• Traditional whole house fans. Typically 24″ in diameter, these fans are designed to work in attics from 1200 to 1800 feet.
• Self contained duct house fans. These smaller fans work to cool spaces from 1000 to 3500 feet, depending on the speed and size of the motor. Again, cool outside air is drawn into the house and hot air is expelled through the attic.
• Window whole house fans. These smaller fans are designed for small spaces (a bedroom, for example). They fit in a window and move air directly outside (not through an attic).
We interviewed five contractors who specialize in heating, ventilation and cooling to get their feedback on whole house fans. We took their suggestions and then additional research to compare specifications and consumer feedback.
One key metric: CFM or cubic feet per minute—this measures the amount of air flow a fan pulls. Sizing this correctly for your home is important.
For the best traditional whole house fan, we recommend Cool Attic’s CX24DDDWT fan. This two-speed, 24″ whole house attic fan is an old school workhorse—it can move up to 4600 cubic feet per minute of air on high speed! (As a comparison, a typical desk fan moves about 600 to 900 CFM.)
What We Liked
• Made in USA.
• Less expensive to run than an air conditioner. This fan uses 150 watts of energy when on high speed. A typical window air conditioner uses four times as much juice.
• Works for attics 1200 to 1800 square feet. That is the typical size attic—but you should measure your own before ordering.
• Two speeds: 3200 CFM and 4600 CFM.
• Rough opening of 26″ x 28″.
• Powder coated finish.
What Needs Work
• Assembly required.
• LOUD! Unfortunately, this is true for most traditional attic fans—the average decibel level is about 85. An equivalent level of noise is that of a garbage disposal. Of course, whether you find the noise level uncomfortable is a matter of personal preference. Some folks like the white noise, since the fan is used at night.
If you prefer something quieter, we’d suggest a self-contained duct system fan—which is what we’ll discuss next.