Does polyiso need to be flush with CMU crawlspace wall?
When state-sponsored program came to put in vapor barrier in my crawlspace (it is 5′ tall around perimeter) they used polyurethane foam to stick poly sheeting to about 15 inches up on the crawlspace CMU wall. They also sealed some cracks and gaps in that wall with foam.
Now I am ready to install vapor barrier to deal with radon. I am also going to put some recycled polysiso I got. Those panels came out of commercial building, so there is no reflective coating on them.
My two questsions:
1. Does poly iso need to be flush with CMU wall? My idea was to put 2X2s and put polyiso over that. THis way I don’t have to scrape off the foam off the walls and remove the sheeting I am going to cover up anyway with new layer.
2. Can new vapor barrier go over the polyiso, or does it have to be under it? If it has to be under it, same question as in 1st one – can I do then vapor barrier all the way to the rim joist and then do 2X2s and polyiso sheets over that?
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