Add vapor barrier after 2" rigid foam on walls?

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jeb101
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Add vapor barrier after 2" rigid foam on walls?

Post by jeb101 » Thu Nov 15, 2018 11:01 am

I have just finished installing rigid foam, and going to spray the joist ends to tie to the top of the rigid foam, but my question is, do I need a vapor barrier after the framing? I'd be putting roxul between the studs. Foam is taped top to bottom, and anything that has a larger gap, has had foam in the gap, then taped to ensure it's well sealed.

Hard to find the definite answer to this one surprisingly.

(2 inch foam + 2x4 framing w. roxul + drywall)


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Shannon
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Re: Add vapor barrier after 2" rigid foam on walls?

Post by Shannon » Thu Nov 15, 2018 9:08 pm

Realistically if it is 2” foam and sealed well with sprayfoam at any gaps then reallynyou should not need a separate vapour barrier but it all depends on what your local building code department requires you to do . They have the final say. If they require you to also install a vapour barrier I would opt for one of the new ones that adapt to the conditions through out the year.
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jeb101
Posts: 156
Joined: Fri Jan 12, 2018 8:13 am
Location: Canada

Re: Add vapor barrier after 2" rigid foam on walls?

Post by jeb101 » Fri Nov 16, 2018 8:22 am

Shannon wrote:
Thu Nov 15, 2018 9:08 pm
Realistically if it is 2” foam and sealed well with sprayfoam at any gaps then reallynyou should not need a separate vapour barrier but it all depends on what your local building code department requires you to do . They have the final say. If they require you to also install a vapour barrier I would opt for one of the new ones that adapt to the conditions through out the year.
I believe I should be OK, I put red sheathing tape on all edges, foam in the bigger gaps, then tape on top. The spray foam guy is going to fill all the way to the top of the foam, so it should make a great seal in that aspect.

Those one way breathable plastics or whatever seem interesting, going to need to find myself a roll when I put my walls up. Thanks for the advice, should help with keeping the roxul in place also.

Cheers

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Shannon
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Re: Add vapor barrier after 2" rigid foam on walls?

Post by Shannon » Fri Nov 16, 2018 3:47 pm

Here is a video showing the general insulation procedure for basements that I like to use.https://www.youtube.com/watch?v=cCFFuL4J0jQ
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