Crawlspace wall insulation
I think I should insulate my crawlspace walls. Originally there was unfaced fiberglass, but it was full of mouse and rat poop, so I removed it to clean everything up. I did the rim joists with cut and cobble foam covered with Rock wool, but the walls are bare. The walls are concrete, 3-4 feet high. On the floor is a 20 mil poly vapor barrier I put down, but I still need to find a way to seal it to the walls. Maybe I’ll tuck it in behind the insulation. The walls always seem to be dry, but moisture from the soil is a problem in the summer without the vapor barrier.
There are some signs that there has been standing water in the past, but probably not above the height of the footers. The soil is clay and there’s no drainage that I can see.
My main question is about what kind of foam I should use. I am concerned about GWP, so I don’t want to use XPS or spray foam. And I only need a relatively small quantity, and I’m having a hard time finding a supplier besides the hardware store. It is a townhouse, so I have only about 140 square feet of wall area. If I do two 2-inch sheets of foam the whole way down, that’s about 9 4×8 sheets of foam. That’s about R15 with 2-inch low density EPS.
Can I use hardware store low density EPS foam for this? Can I use polyiso? Or should I seek out higher density EPS or reclaimed form?
Almost forgot to mention:
I’m in Zone 5, and I’m making this a “conditioned” crawlspace, but since I have hydronic heat the conditioning is by means of continuous exhaust ventilation and maybe a dehumidifier if humidity continues to be a problem.
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