Home & Garden

How to air seal bathroom exhaust fan?

  • Last Updated:
  • Nov 5th, 2015 8:46 am
Tags:
None
Member
Oct 3, 2012
233 posts
50 upvotes
GTA

How to air seal bathroom exhaust fan?

I was up in the attic checking things out before the winter and noticed that our bathroom exhaust fan was installed without a vapor barrier. The venting looks correct in that it is insulated. I would like to add a barrier before the winter but how should I go about doing so? I really don't want to remove the fan to install the barrier.
I was thinking I can buy a vapor barrier boot the size of the fan or those available for potlights, and cut it to fit around the fan housing and tuck tape the crap out of it to the drywall and adjacent joist. Does this sound like a good idea?
5 replies
Deal Expert
Aug 2, 2001
18944 posts
10526 upvotes
With enough tuck tape you can probably achieve a good seal on the fan. To be honest - I think for older homes most do not have the vapour barrier boots around everything. I have a friend that always reminds me - is it really worth fixing a pinhole when you have 38 more you will never fix?

There is no doubt you will see little noticeable return on your investment - and you are talking of a good amount of time to get into the attic, clean out the insulation around it, cut the boot so it slides over, tuck tape the heck out of it, then recover with insulation. If you are in an older home with poor air sealing, I think it might be a waste of time until you do an actual bathroom reno.
Deal Fanatic
Nov 17, 2012
5379 posts
4994 upvotes
Toronto
Is the duct from the fan to the outside rigid or that crap flexible stuff?

The fan housing is air tight. It does not need to be covered with vapor barrier. The poly is under your drywall and should be sealed to the fan body. At least this is my recollection from my Panasonic fans.

Covering it with plastic is going to trap air (bad) and possibly cause the fan to overheat (bad).
Deal Expert
Aug 2, 2001
18944 posts
10526 upvotes
torontotim wrote: Covering it with plastic is going to trap air (bad) and possibly cause the fan to overheat (bad).
I am not sure that using a vapour barrier boot would make the situation any worse since the fan would otherwise be completely covered in insulation.
Member
Oct 3, 2012
233 posts
50 upvotes
GTA
Sorry I should have elaborated a bit more. This fan was already sort of falling through the ceiling. I'm not sure why but the fan box was not screwed to the joist or sealed to the poly properly. I purchased a potlight vapor boot and cut it to fit and secured the fan box to the joist properly. I then tuck taped it to high hell. This was before reading these comments, I did not know that fan boxes were considered air tight. Hopefully it does not overheat as one poster mentioned.
Deal Fanatic
Nov 17, 2012
5379 posts
4994 upvotes
Toronto
I was probably wrong. I just recall something about my Panasonic fans being IC rated and air tight but it was 7 years ago.

Top