Take the 2-minute tour ×
Home Improvement Stack Exchange is a question and answer site for contractors and serious DIYers. It's 100% free, no registration required.

I'm adding a bathroom exhaust fan, which is being mounted in the ceiling of the bathroom (in the attic) and venting out through a vent in the wall.

right now, there is a vapour barrier (paper) between the insulation in the attic and the drywall. I will have to break this of course to mount the fan housing, but my question is, what do I do after? Should I put a vapour barrier around the exhaust fan and seal it to the paper?

I was also going to put insulation back over top of the exhaust fan - is that correct to do, or anything to watch out for? The vent pipe I have is a 4" insulated duct that will go to an outside vent (which I just installed this weekend).

share|improve this question
add comment

2 Answers 2

up vote 2 down vote accepted

Check the directions/specifications of your exhaust fan, it should say if it is rated to have insulation next to or on top of it.

It would probably be a good idea to seal the vapour barrier back around the fan.

share|improve this answer
2  
Interestingly, says nothing about insulation in the instructions that came with it, but the Broan website has it: any of their fans can be covered up to R40 (broan.ca/support-faqs-500.asp#9) –  gregmac May 4 '11 at 6:27
add comment

The important part of the vapor barrier is to keep outside moisture from reaching the cooler drywall, condensing, and creating mold on the drywall. Anywhere I've ever put a hole in the drywall, e.g. for electrical boxes, we just cut the paper around the protrusion. Any excess was either cutoff or folded back. For whatever reason, building inspectors don't seem to worry about condensation on the back of an electrical outlet, go figure.

If you're especially paranoid, you can install some fire blocking between the joists on either side of the fan housing, screw a piece of drywall on top (with the vent protruding) and install some insulation on top of that. This would minimize fire and moisture risks, though I've never personally seen anyone take it this far.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.