# Vapour barrier in bathroom



## Hepeto (Mar 17, 2019)

Hi, 

I am replacing the old bathroom ceiling fan and had to remove the whole housing unit.

I was able to get the old one out but now I realized the vapour barrier is not intact. Me yanking out the fan didn’t help, but to me it seemed this wasn’t properly installed to begin with. 
I also noticed the insulation to be moldy.

- can I live with this or is it advisable to remove the entire drywall ceiling and re-do this?

- if I only line the hole for the new fan with 6mil sheathing how do I manage to efficiently plug the hole for the duct and electrical? Do I need to cut around the area to put the plastic cover back in?


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## Nealtw (Jun 22, 2017)

Do you have access to the attic?


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## Hepeto (Mar 17, 2019)

Unfortunately not, there seems to be limited space in the ceiling - Less than 10 inches clearance 

Not entirely sure if it is really moldy or just dust and grime accumulated over the years. It’s very dry in there


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## Nealtw (Jun 22, 2017)

Hepeto said:


> Unfortunately not, there seems to be limited space in the ceiling - Less than 10 inches clearance
> 
> Not entirely sure if it is really moldy or just dust and grime accumulated over the years. Itâ€™s very dry in there


When house air gets past insulation it will drop off moisture and the dust in the insulation. even if there is a little mold if dry, you have already spread the spores. When I have changed one like that I found the poly had just been cut around the box. So I just made sure all the holes in the box were sealed with fire rated caulk from the inside, then I put aluminum tape from the inside of the box down onto the ceiling. just enough for the grill to hide the tape.


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## Hepeto (Mar 17, 2019)

Would you suggest to take it all out?

I was thinking to cut around the area to see what’s behinf it and to give me more access to line it with poly


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## Nealtw (Jun 22, 2017)

Hepeto said:


> Would you suggest to take it all out?
> 
> I was thinking to cut around the area to see what’s behinf it and to give me more access to line it with poly


 I wouldn't, I think no matter how much you destroy trying to seal it there will always be something that just hard to seal. I would seal all the holes that would let air out of the box from the inside and then try to stop air that might just get by it at the ceiling.


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## Bud9051 (Nov 11, 2015)

Although bathrooms have a lot of moisture, assuming a shower, by adding a delayed off switch to keep the fan running for 20 minutes after being turned off that moisture risk drops significantly. 

The other issue which they have learned is more important than a vapor barrier is air sealing. What you describe sounds more like an air leak issue than a vapor barrier issue. *Here's* a good link.

Bud


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