It is the simplest way to cool a house: bring the cool night air in, push the hot air out. Here is exactly how the air moves, and what it takes to do it well.
A whole house fan is a large exhaust fan in an upstairs ceiling. When it is cooler outside than inside, you open a few windows and switch it on. It pulls outdoor air through your rooms and pushes the hot indoor air into the attic, where it leaves through the roof vents. CentricAir’s sizing guide matches each model to a home size, so you can pick the right fan by square footage.
Anyone who has opened every window on a summer evening and waited for a breeze knows the idea. A whole house fan skips the waiting. It makes its own breeze, strong enough to pull cool air through every room and flush out the heat your walls, floors and attic soaked up during the day.
What is a whole house fan?
A whole house fan is a powerful exhaust fan mounted in the ceiling between your top floor and the attic, usually in a central hallway.
It moves thousands of cubic feet of air per minute (CFM) out of the living space and up into the attic. That air has to be replaced, so fresh outdoor air flows in through whichever windows you open.
People often mix it up with an attic fan, but they do different jobs. An attic fan only vents the attic. A whole house fan changes the air in the rooms you live in. Our attic fan vs. whole house fan guide covers the difference.
Prefer to watch? This short animation from CentricAir shows the same airflow in motion.
How does a whole house fan work, step by step?
The fan lowers the air pressure inside the house slightly, and outdoor air rushes in through the open windows to even it out.
That steady flow carries heat out of every room it passes through. Here is what a typical evening looks like.
- Wait for the crossover.Once it is cooler outside than inside, usually after sunset, it is time to run the fan.
- Open a few windows.Start with the rooms you want coolest, like the bedrooms.
- Turn the fan on.The damper opens and the fan starts pulling air up through the ceiling grille.
- Let it run.Outdoor air crosses the house toward the fan and pushes the day’s heat, and the attic’s heat, out through the attic vents.
- Close up in the morning.Switch it off before the day warms up. The damper closes, and the house starts the day cool.
Where does the hot air go?
Into the attic, and out through the attic’s vents. That is why attic ventilation matters as much as the fan itself.
The Department of Energy’s Building America Solution Center recommends at least 1 square foot of net free vent area for every 750 CFM of fan airflow. Net free means the open area left after screens and louvers, which is smaller than the vent’s outside size.
Every CentricAir product page lists the vent area that model needs. The CentricAir 2.0 calls for about 2.5 square feet, and the CentricAir 3.4 for about 4.0. If your attic comes up short, an installer can add vents before the fan goes in.
Why do you have to open windows?
Open windows are where the replacement air comes from. With the house closed up, the fan has nothing to pull in.
Building America’s guideline is at least 4 square feet of open, screened window for every 1,000 CFM. A 3,242 CFM fan like the CentricAir 3.4 needs about 13 square feet, which is three or four ordinary windows opened partway.
You also get to steer the cooling. Open only the bedroom windows at bedtime, and most of the fresh air goes through the bedrooms.
What size whole house fan do you need?
Match the fan to your home’s square footage and number of stories.
Every CentricAir model page lists the home sizes that model is built for. A 2,000 square foot single story home, for example, falls within the range of the CentricAir 3.4, 4.0 and 4.0 ECM. Then check that your attic has enough vent area for the fan you pick.
| Model | Airflow (CFM) | Watts | One story, up to | Two story, up to |
|---|---|---|---|---|
| CentricAir 1.5 | 1,263 | 143 | 700 sq ft (one room or bonus room) | n/a |
| CentricAir 2.0 | 1,918 | 207 | 900 sq ft | 1,400 sq ft |
| CentricAir 2.7 | 2,709 | 288 | 1,350 sq ft | 1,800 sq ft |
| CentricAir 3.4 | 3,242 | 382 | 2,500 sq ft | 3,400 sq ft |
| CentricAir 4.0 | 3,921 | 623 | 3,000 sq ft | 4,400 sq ft |
| CentricAir 4.0 ECM | 4,146 | 749 (high) | 3,000 sq ft | 4,400 sq ft |
Airflow is the California Title 24 rating listed on each model’s page at centricair.com. Not sure which fits? Try our sizing guide.
When does a whole house fan work best?
In places with warm days and cool, dry nights.
Whole house fans pay off most where summer nights cool down, often to about 67°F or below, and the Department of Energy’s Building America program rates dry western climates as an especially good fit. Any evening that is cooler outside than inside is an evening the fan can do the work.
Most owners switch the fan on once it is cooler outside than in, run it through the evening or overnight, and shut it off in the morning. On hot, muggy nights that stay warm, the air conditioner is still the right tool.
What keeps it quiet and sealed?
Where the motor sits, and how well the ceiling opening closes when the fan is off.
Traditional whole house fans mount the motor and blade right in the ceiling opening, just above your hallway. CentricAir systems come with sound absorbing acoustical ductwork between the fan and the ceiling grille, so the motor is not sitting directly overhead.
When the fan is off, the opening needs to stay sealed so conditioned air does not leak into the attic. Building America stresses an insulated, well sealed damper for exactly this reason. Every CentricAir system includes an industrial grade backdraft damper, and select models offer a cold climate damper upgrade.
What does an installation look like?
For most homes it is a short job, and many owners do it themselves. Plan it for the morning, when the attic is cooler.
CentricAir says a typical installation takes about 90 minutes and needs no framing. This video walks through every step, from cutting the ceiling opening to mounting the fan in the attic.
Rather have a pro do it? Find a whole house fan installer near you.
Match your square footage and number of stories to a CentricAir model.
Watch more from CentricAir
More videos from the CentricAir YouTube channel. Click any video to play it right here, or subscribe for new installs, tips and product walkthroughs.
Frequently asked questions
Do I need to open every window when the fan is running?
No. You need about 4 square feet of open window for every 1,000 CFM of airflow. Open the windows in the rooms you want cooled first.
Can I run a whole house fan and the air conditioner at the same time?
No. The fan would send the cooled air straight into the attic. Use the fan when it is cooler outside than inside, and close up and switch to AC when it is not.
Does a whole house fan make the attic hotter?
It does the opposite. The steady airflow pushes the day’s trapped attic heat out through the vents, as long as the attic has enough vent area.
How long does a whole house fan take to cool a house?
A fan sized to your home moves a lot of air, so the air cools fast. Walls and furniture give up their heat more slowly, so the house keeps cooling through the night.
Can I install a whole house fan myself?
Many homeowners do. CentricAir says a typical installation takes about 90 minutes and needs no framing.
Keep reading
Sources
- U.S. Department of Energy, Building America Solution Center (PNNL), Whole-House Fans, updated Sept. 29, 2022.
- California Energy Commission, 2025 CF1R-NCB-01-E Prescriptive Newly Constructed Building form, and 2022 Energy Code Section 150.1(c)12, Whole House Fans (Energy Code Ace).
- CentricAir product specifications and prices, centricair.com, accessed Sept. 2026.