We've now prepped for the basement slab pour with a combination of gravel, poly, Styrofoam and rebar. Next up the plumber will be back and we will get the heat pipes laid in. After another inspection we can pour the slab. All of this is intended to stay ahead of the framers so that once the roof is on they can frame the basement walls immediately. It makes the job of every trade yet to come much easier when we can accelerate the slab and basement buildout.
We have modeled an r5 insulation under the slab. Beyond this we find diminished returns on heat loss. The code currently requires an r16 level of insulation and I've never understood why. Apparently radiant installs have decreased dramatically since the code change. Another of many examples of government meddling that wasn't needed and now is actually a counterproductive force in how homes are heated.