Looking to build a new home in California, and am trying to understand underfloor insulation. My understanding is that the recommendation is to put insulation under the slab. However, I’ve also seen insulation over the slab in conjunction with a plywood subfloor. This seems to be a good thing when laying down hardwood floors and I would prefer a little give in the floor? I also seem to recall an article in FHB about an engineer with seismic concerns with the underslab insulation. Thoughts?