How thick should EPS foam insulation on basement walls be?

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How thick should EPS foam insulation on basement walls be?

Derrick R March 17, 2021Last updated: March 22, 2021

I'm researching about what type of rigid insulation to use when finishing my basement. I was on a website of an eps insulation manufacturer and under their technical/spec section for this particular rigid panel it says the vapour permeablility for 1" is 0.5 perms. would using 1" panel be sufficient instead of the recommended 2"?

Responses (3)

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Derrick R March 22, 2021, 11:58 a.m.

Thank you for your insight. Obviously I don't want to spend more money than necessary so if the 1 inch was sufficient that's what I would choose. But if minimum 2 inches is what's suggested then that's what I'll go with. Thanks again!

Emmanuel Cosgrove
Emmanuel Cosgrove March 23, 2021, 6:13 p.m.

Happy to help Derrick.  Worth considering is that if you are in a cold climate, then the added investment of going from 1 inch to 2 inches will pay for itself in a few years at most in heat savings, if not even in the first year. I'd do it anyway for the moisture though.