Perlite as insulation
I am wondering about whether it may be okay to use perlite as insulation under a basement slab. I am planning a Passive House and under the current plan, I would use 4 inches EPS. According to passive house, the EPS would also be under the footings. I am a little concerned about the structural stability of EPS under the concrete footings. I am considering using perlite granules (R-2.7/in), maybe about 6 inches of it underneath the entire foundation. Are there structural issues to be concerned with?
Another application is adding perlite into the concrete mix that is to be poured into the ICF forms. In the original plan, I planned to add 3 inches of EPS on the outside of the ICFs, but this makes my walls about 15 inches thick. I am wondering if I can add enough perlite in the concrete to bring the R-value of the concrete to a level that I can skip the additional EPS and again without sacrificing strength.
Any comments or advice? Thanks in advance