Is a vapor barrier necessary under a concrete slab with foam insulation and if so, where does go?
We're soon building a slab on grade foundation for our new cabin in Montana and I've decided to sit it on a 4" EPS foam insulation so the slab will retain some passive solar heat from the south facing windows in winter, avoiding having to put too much heat in to keep stuff from freezing. There's a bed of compacted grav...