Hi all,

Ive seen both on the FHB and GBA websites so im kind of confused on which to do. I am in climate zone 5b and have no bulk water issues. My current crawlspace is masonry block foundation walls and dirt floor. I’ll be using a 15 mil poly for vapor barrier, seams overlapped and taped. I’ve seen both rigid insulation on the walls then followed by vapor barrier and I’ve also seen vapor barrier to the walls followed by the rigid insulation. 

my plan was to go up the walls by about 1 foot with the vapor barrier. I have approved foam board adhesive for the rigid insulation. I was going to use double sided tape for the vapor barrier. The only thing is, I’ve done a mock run and the foam board adhesive doesn’t seem to dry when applied between the 2” XPS and the vapor barrier likely because they’re both vapor barriers. I was really hoping to avoid having to use mechanical fasteners just due to hassle. 

So perhaps I could attach the rigid foam to the foundation walls and then using the double sided tape on the rigid insulation? Just wanted to make sure it wasn’t an issue if the rigid insulation could absorb any vapor from the walls. I suppose it could still potentially dry to the inside a bit. 

I’ll be sure to tape the seams of the rigid insulation and then I’ll tie in the rim joist insulation to the wall insulation for continuous insulation and vapor/air barrier system. Thanks.