How to insulate between joists on concrete?
I’m renovating a half bath in my Maryland home which was built in 1967. The bathroom, which is adjacent to the garage, is built slab-on-grade with 2×4 joists on 1 brick piers. How should I insulate between the joists? Should I use rigid foam insulation with tape and spray foam? Do I need a vapor barrier? I’m worried that if I put down plastic against the concrete that there will be mold problems. (I think that the original framing is in decent shape because there was a lot of airflow which dried things out. The house is not tight.)
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