Is rigid foam necessary under concrete slab in Central Virginia?
We are having a house built in Central Virginia. The builder uses a CMU stem wall and then pours a concrete slab. They isolate the slab from the stem wall with 1" XPS for R-5. This is all that the building authority requires. My question is it worth the extra cost to have the builder install R-5 on the entire stem wall and then 2" XPS or EPS under the slab for R-10?