I would like to insulate my whole-house fan in the winter. I've see insulating covers that you can attach with magnetic strips or velcro, but the look does not appeal to me and I don't trust how well a velcro seal would work (our fan is aluminum).

I'm curious if there are other ways to insulate a whole-house fan for the winter.

I had an idea to make a foam insert and drop it in from the top. I'm imagining spraying some expanding foam into a wood frame. The frame would rest on top of the frame around the hole for the fan. I could even mount it with some hinges so it's easy to open and close. Not sure how feasible this is.

edit: Checked the attic and saw that the fan motor extends pretty high. The insulation would need to be attached to the bottom of the fan opening. Looking like the cover might be my only option.

3 Answers 3


Skip the expanding foam and buy pre-made foam panels from your local HI store. Layer them up for more insulation and cut them to size with a knife or saw (I just use a drywall saw). You can enclose them in a wood box on top if you'd like, but they're rigid enough that they'll stay where you leave them without building an enclosure (unless you turn the fan on).

Just saw your edit about the motor. You can build up the foam panels into a tent. But if you can get a cover designed for a whole house fan, that may be your best option.


In my opinion, the best solution would be to build a box out of rigid insulation board that has a hinged lid. This allows plenty of blown-in insulation (cellulose, fiberglass, rockwool, etc.) to be installed in the attic without falling into the whole-house fan.

The hinge allows to lid to be blown open by the fan when operating, which means you won't have to crawl in the attic over the blown-in insulation to open/close the lid seasonally. The velcro seal on the ceiling would be a good supplement to this solution.


A simple solution is a hot water heater insulating blanket. It probably is not as efficient as the foam panels, but it does help. In addition, if someone accidentally turns on the fan. It will just blow off.enter image description here

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