Vapor Retarder for Basement Walls
Hi – I am installing R-10 2 inch XPS foam boards on the interior outer walls of my walk out basement. I am then installing metal 2×4 studs which will be filled with R-15 Rockwool for a R-25 total. I am doing this on this new construction so I don’t have to insulate the basement ceiling as some here pointed out more than 50% of the basement is below grade, and my 8 foot basement is 80% below grade.
My question is before I cover with sheetrock, or cover with another product if someone could suggest one as this is an unfinished basement, do I have to put plastic over the Rockwool? I am thinking I don’t since the 2 inch foam board acts like a barrier and though Rockwool supposedly doesn’t mold, I am thinking it’s not good to have two barriers. The rim joist will be sprayed above – I want closed cell but the insulation guy says I can use open cell. I think since is trying to talk me into doing the first floor walls with open cell, he can kill two birds with one stone if the open cell people are on site.
Thanks everyone in advance.
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