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Community and Q&A

Basement Wall Insulation & Finishing

Hanwich | Posted in Energy Efficiency and Durability on


I’ve been reading around to try and gather information on basement insulation and wondering if the following would work…

I have already installed and taped 1″ xps and am planning on adding 2″ polyiso (non-foil, fibre-faced) using an adhesive (great stuff) to secure it.
Q1: Is it okay for me to use non-foil poly iso? My main motivation is that I can get it cheaply and recycled and my next cheapest option is 2.5″ foil-faced poly

I’ve seen that some folks will then add strapping secured with tapcon to the concrete through the foam.
Q2: I’m wondering if I can skip the strapping and adhere 1/2″ drywall directly to the foam?
If so, would great stuff work for this as well?

Is there something I’m missing here?

Thanks in advance!

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  1. Expert Member
    Michael Maines | | #1

    Yes, check out Hilti IDP fasteners; they're made for this situation.

    No problem with fiber-faced polyiso. It's somewhat vapor-permeable so be careful what materials you put inboard of that.

    Any foam other than DuPont Thermax needs to have a fire-protective layer on the interior. 1/2" drywall is the usual choice. It can be glued to the foam but strapping is more reliable.

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