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How do Install Rigid Foam on top of the Vapor Barrier

Posted: Sun Jul 03, 2016 4:03 pm
by khanka
I'm trying to frame my basement and drawing up plans. My basement already has a polytarp-super six vapor barrier installed. Do I still need to install rigid foam insulation to top of this? If so how do I do this as the vp is kind of bulky in areas and adhesive wouldn't probably give me a straight wall (don't know if the rigid foam insulation being straight is even necessary) or would I use a plastic anchor (same concern with the straightness)? Thanks.

Re: How do Install Rigid Foam on top of the Vapor Barrier

Posted: Sun Nov 17, 2019 1:59 pm
by manthano
Can you space rigid foam board away from your VB? Say by running a 2x2 weather treated board spaced away from VB?

Re: How do Install Rigid Foam on top of the Vapor Barrier

Posted: Sun Nov 17, 2019 8:55 pm
by Shannon
HMM so when you say VB do you actually mean Moisture barrier? If its against the concrete wall then it is a moisture barrier. Poly VB are placed on the warm side of a wall right under the drywall.

I believe this is what you are referring too (moisture barrier) . If your local area will allow you to use rigid foam in the basement as a moisture barrier and for some insulating value then I would remove the poly one. Allow the wall to dry out a couple of days and then install the rigid foam onto the concrete . Some areas will allow you to skip the VB after if you use enough rigid foam and it is sealed well, if they insist on needing a vapour barrier as well then I would use one of the new "smart barrier" types. Which will allow the wall to reach if it needs to. Check all of this with your local building code office before deciding how to proceed.