Insulating a Concrete and Framed Basement
I have learned a lot from all the great info here, but I haven’t seen an answer to my particular situation:
We have an addition built about 5 years ago where the basement consists of 6′ tall poured concrete walls below grade and about a 3′ tall section of 2×6 construction above grade. That was originally finished with “blanket” insulation hanging on the concrete and fiberglass bats and drywall on the framing.
We are now working to finish the space, so I am replacing the concrete insulation with polyiso and plan to frame a floor to ceiling wall inside that. That will effectively hide the drywall+framed section (which has a vapor barrier on the exterior, but nothing on the interior of the sheathing.)
So, the questions:
1. Should I just leave the drywall and fiberglass in place? Will that create a moisture issue behind the new wall? Alternately, I could remove the drywall (and the fiberglass?) and run polyiso continuously over the studs (or cut and cobble).
2. If I stop the polyiso at the top of the concrete and also place a horizontal piece on the sill, can I seal to the drywall (can foam) or should I at least cut back the drywall and seal to the sill plate?
Sorry for the long description, but I appreciate any help!
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