Rigid foam insulation for basement


Old 07-26-17, 08:49 PM
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Rigid foam insulation for basement

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Is it a good idea? Because concrete is porous and would transmit moisture, would it be a good idea to use foam between the concrete and the stud so the stud won't touch the concrete and absorb the moisture?
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Old 07-27-17, 02:32 AM
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Its done, it's expensive, it's overkill, there are other methods that work in a basement. It does not resolve a water issue!
Old 07-27-17, 09:07 AM
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It is a vapor retarder and provides a thermal break in thick enough layers, which does prevent condensation from forming.

PT wood is required when wood touches concrete.
Old 07-27-17, 12:34 PM
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It's a good idea for cold climates. You would want to ensure that the exterior side of the foundation has been waterproofed, and as mentioned, that there are no preexisting moisture problems inside. You would want to tape all the seams and air seal the perimeters, because you don't want any air exchange to cause condensation behind the foam. And at least in the US, due to fire codes you need to use a foil faced product like Thermax if it will be exposed anywhere, such as in an unfinished mechanical room. The framing in front of the foam can then contain all your electrical and plumbing. Its a nice way to do it.
Old 07-31-17, 10:26 AM
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I'm in the middle of my own basement finishing project and did also install Rigid Foam board against the poured concrete walls and then framed in front of them, with PT bottom plate on the concrete. And being in Buffalo, NY with colder winters I still plan to add batts of insulation before sheetrocking.

One thing to remember is if you add the Rigid board is to use the right foam board adhesive. Look for Locktite PL 300.

And don't forget to fireblock any holes, seams, etc in your framing.
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