Do I need to insulate under the footings of a frost protected shallow foundation?
Hello,
I’m designing a FPSF in Southern Vermont (AFI 2300). I want to fully insulate the radiant slab by including 4″ XPS under the footings but this seems to conflict with the FPSF principle of relying on heat transferring through the footing to stabilize the ground temp. My next thought was to use the FPSF design g...