What is a Whole House Fan and How Does it Work?
What is a whole house fan?
A whole house fan is a large fan installed in the ceiling of a home. It is used to pull outside air through open windows and exhaust it into the attic
It is separate from your AC system and does not have a filter as the outside air is entering from a window.
Dampers close off the opening in the ceiling when the fan is off so hot air and dust from the attic do not come into the living area of the home.
Benefits of a Whole House Fan
Now that you know what a whole house fan is, the next question is why would you want to pull all this air through your home?
Two reasons: indoor air quality and cooling.
The first point seems obvious to anyone who cooks or has pets in the home… sometimes you just gotta get some fresh air! But for everyone else did you know the EPA reports pollutants are often 2 to 5 times greater inside your home that outdoors?
A properly sized whole house fan will exchange the air in your home in 3-4 minutes, giving your home a fresh start. No matter the temperature outside, running the fan for a few minutes clears out offending odors.
Cooling is the reason most people get a whole house fan.
Cooling happens in 3 parts: air movement over your skin (feel 5-10 degrees cooler than still air instantly), cooler outdoor air replacing hot indoor air, and thermal mass cooling.
Thermal mass cooling is probably the most beneficial but least discussed method.
Normally your home retains most of the heat the sun bakes into it during the day. This means your AC is running at night and your attic is acting as a nice warm blanket for your house, trying to keep it nice and toasty while you keep pumping cool air in with the most energy hungry appliance you own!
(Spoilers, it’s the air conditioner).
Circulating cool outside air through your house and attic overnight lowers the resting temperature of the framing and insulation by up to 40 degrees compared to a home without a whole house fan.
Summarizing the Energy Use Math:
With a whole house fan, your AC doesn't run at night and since the attic is cooled, you can wait several hours later in the day to turn it on than you normally would too.
You can exchange 5-6 hours of AC use per day for 2 hours of a whole house fan on high and 6 hours on low during the summer months. A typical AC unit on a mid-sized home uses 6,240 watts per hour compared to 490 watt on high and 88 watts on low for a QuietCool Stealth whole house fan.
At the PG&E base rate of $.24 per KW this saves you over $8 per day. And we both know you don't stay in PG&E's base rate!
We have found that for a typical home installing a whole house fan pays for itself in 1-2 years in a DIY scenario and in 2-4 years when purchased with installation.
That's a nice little 40+% return on investment.
How to Use a Whole House Fan
- In the evening open a few windows 3-6" in the occupied areas. • Turn on your whole house fan. It pulls cooler outdoor air into your home through the windows, across your living space, into the attic, and out the attic vents.
- Run the fan on high initially to clear out the stale air, or as long as you enjoy the breeze.
- Leave the fan running on low overnight to cool the thermal mass of your home.
- In the morning close your windows and enjoy your day!
Types of Whole House Fans
Traditional whole house fans are framed into the ceiling and have the motor and blades near the ceiling. They have the disadvantage of being loud and often require cutting a truss to install.
Ducted whole house fans are the new and improved version with many benefits. Because the fan is suspended in the attic the noise level is much lower.
These fans usually have more efficient motors and are designed to fit between the trusses so no cutting of your home's framing is required.
There are several brands of ducted whole house fans available, but the brand Cosmic Comfort is most familiar with is QuietCool. They are the original fan of this design and still feature a fantastic combination of price, noise level, energy efficiency, and warranty.
This guide covers the what, why, and how of whole house fans. Click Here for a QuietCool buying guide or fill out the contact form below to request more info or speak to an expert on whole house fans.