A whole house fan earns its keep in summer. In winter, its only job is to stay sealed. Here is how to check yours and stop the drafts.
In winter, a whole house fan should stay off and sealed. The Department of Energy’s Building America program notes that an unused whole house fan can leak heat through its dampers unless the ceiling stays well sealed and insulated. If you feel a draft at the grille, add an insulated cover or upgrade the damper. CentricAir fans come standard with an R5 insulated gravity damper, and an R13 motorized Cold Climate Damper is available.
For most of the year you will not think about your whole house fan once the weather turns cold. That is fine, as long as the opening is sealed. A whole house fan is a large hole in your ceiling that leads straight to the attic, and in January that attic can be as cold as the outdoors.
Do whole house fans lose heat in winter?
They can, if the damper and the ceiling around it are not sealed and insulated.
Building America puts it plainly: when the fan is off in winter, a whole house fan represents a potential energy loss due to leakage and heat loss through the dampers. It says units must be installed so the ceiling remains well sealed and insulated when they are not in use.
ENERGY STAR notes that sealing and insulating can provide up to 10% savings on annual energy bills. A drafty fan opening is one of the easier leaks to fix.
How can you tell if your fan is leaking?
Feel for a draft at the grille on a cold, windy day.
- Cold air falling from the grille. The simplest test. Hold your hand under it.
- Louvers that rattle or sit open. Older fans often use thin metal louvers that do not close tightly.
- No insulation over the damper. From the attic, check whether the damper or box is insulated and sealed to the ceiling.
- Dust streaks around the grille. Air moving through gaps leaves a dirty outline over time.
Should you cover a whole house fan in winter?
If it leaks, yes. If it has a tight, insulated damper, it may not need one.
There are two common approaches. A cover can go over the grille from inside the house, which is easy to add and remove with the seasons. An insulated cover or box can also go over the fan from the attic side, which keeps the attic insulation layer continuous. Building America recommends that a fan without a built in insulated cover get an insulated cover, either purchased or built.
Before you buy a cover, check what your fan already has. Every CentricAir system includes an R5 insulated gravity backdraft damper, designed to keep attic air out of the living space when the fan is off.
What is a cold climate damper?
A heavier duty, motorized damper for homes with real winters.
CentricAir’s Cold Climate Damper uses a heavy duty actuator tested to 60,000 cycles and a door insulated to R13 to help ensure an air tight seal whenever the fan is not in use. It can be installed vertically or horizontally, and it is available with the CentricAir 2.0, 2.7, 3.4 and 4.0 and the QA-Deluxe 3300, 4800, 5500 and 6500 as a $199 upgrade.
Building America also recommends sealing between the fan or damper box and the framing and drywall with foam weather stripping or spray foam. Even a great damper leaks if the gaps around it are open.
Can you run a whole house fan in winter?
Rarely. Running it while the heat is on sends your heated air into the attic.
On a mild day when you want to air out the house, a few minutes with the windows open will do it. Otherwise, leave the fan off through the heating season and keep it sealed. Building America also advises against running a whole house fan together with air conditioning in humid climates, and the same logic applies to heating: you are paying to condition air the fan would push straight out.
Should I remove my old whole house fan?
Only if you never use it and cannot seal it well.
Older louvered fans are the usual culprits for winter drafts. If you still like the summer cooling, replacing an old fan with a modern sealed and insulated unit keeps the benefit and fixes the leak. If you truly never use it, sealing and insulating the opening is an option. An installer can look at the damper, the framing and the insulation and tell you which makes more sense.
Every CentricAir system includes an R5 insulated damper. An R13 Cold Climate Damper is available.
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Frequently asked questions
Should you cover a whole house fan in winter?
If your fan’s opening is not well sealed and insulated, yes. Building America notes that an unused whole house fan can leak heat through its dampers unless the ceiling stays well sealed and insulated.
Can you run a whole house fan in winter?
You can on a mild day when you want fresh air, but running it while the heat is on sends heated air into the attic. Most owners leave it off and sealed through the heating season.
Do whole house fans lose heat in winter?
They can. Building America calls an unused whole house fan a potential energy loss through leakage and heat loss at the dampers, which is why insulated, tight sealing dampers matter.
What R value is a CentricAir damper?
The standard CentricAir gravity backdraft damper is insulated to R5. The optional motorized Cold Climate Damper is insulated to R13.
Should I remove my old whole house fan?
If it is an older louvered fan that leaks air and you never use it, replacing it with a modern sealed unit or sealing the opening are both options. Ask an installer to look at the damper and insulation first.
Keep reading
Sources
- U.S. Department of Energy, Building America Solution Center (PNNL), Whole-House Fans, updated Sept. 29, 2022.
- ENERGY STAR, Seal and Insulate with ENERGY STAR.
- CentricAir Insulated R5 Gravity Backdraft Damper and Cold Climate Damper product pages, accessed Sept. 2026.
- CentricAir product specifications and prices, centricair.com, accessed Sept. 2026.