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I would like to replace the bathroom fans that came with my 2019 new construction home. I have successfully replaced the basement bathroom fan and it went well enough. The rest of the fans to be replaced are upstairs, and above them is the attic, which is full of blown in insulation.

When I pull the old fan out, how do I keep the attic insulation from falling through the hole into the bathroom below?

The bathrooms are on the opposite side of the house from the attic access, and the insulation fully covers the joists, so going up to "fix" the insulation when I am done would be a project in itself that I would like to avoid.

Michael Sadowsky
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5 Answers5

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I feel your pain. In my location most of the homes have blown in insulation. There is no magic trick to keep the insulation from falling. Do the replacement if you must and replace the insulation if a lot is lost.

RMDman
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RMDman is right, but it's very important that you replace the insulation over your fan. If you don't, your fan will constantly leak unconditioned air into your room (in one direction or the other, depending on season). Condensation can occur and cause damage. Your fan may be more noisy and less efficient.

One strategy is to carefully remove the old fan, then build an enclosure with fiberglass batts around the opening, against the blown insulation and roughly the height of the fan housing. Lay one or more batts over the box. It doesn't need to be tight against the fan housing, but it should be reasonably well sealed against drafts. This can be done from below with a little patience and creativity.

Otherwise, this might be a good time to establish a route from your attic access. Lumber securely fastened to the trusses can create a path for work and inspection later.

isherwood
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As I noted in another recent post: Depending on why you are doing this, replacing the blower may be a cheaper and easier operation than replacing the whole exhaust fan unit.

If you do need to replace the whole unit: ideally, a suitable fire-resistant box was placed over the fan unit before insulation was blown in, for just this reason. But that doesn't/didn't always happen.

If it didn't, the best answer I have is that you can go up and dig your way to the fan, clear the insulation from around it, do the replacement, possibly install that barrier box, and then shovel insulation back to where it belongs... or, as others have said, just accept that a lot of insulation will fall through, try to capture it in a bag as it falls and/or bag it after it falls, then carry it back up and toss it back into place when you're done.

Hopefully someone else has a more clever solution for that last case, though .

keshlam
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If you only need a temporary cover, tape plastic sheeting to cover the hole from underneath or better and if the hole is small enough an opened garbage bag works best as you can easily close the bag holding anything that may have fallen through. Letting the bag hang down so that the everything goes to the bottom, again making it easier on yourself.

Also be aware that while it may be legal, its extremely stupid to let the air along with the moisture collect in the attic, attach duct work so that the air is exhausted outside of the structure.

Ronald Smith IV
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I attach a galvanized duct to the fan exhaust that extends above the insulation. A plastic flapper valve that easily blows open when the fan is on and closes when the fan is off would be good. I can't remember which hardware store I found these valves at.

blacksmith37
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