Basement Wall EPS Thickness – GreenBuildingAdvisor

Hello,

I’m insulating my basement walls, and I’m aiming for at least R-21. I’d prefer to minimize foam usage, so I was wondering what the minimum thickness of foil faced EPS I could get away with is. I’d prefer to use 1/2 inch faced rigid foam with 2×6 framed walls, but I wasn’t sure if that’d be enough to avoid moisture problems in the batts. Let me know what you all think.

Thanks,

Isaac