Insulating a radiant heated floor (below slab) -- use foam board?
Quick question to all the radiant floor (basement concrete) experts out there.
I'm in the process of having our basement floor broken up, dropped down a foot and re-poured with a PEX in-floor heating system installed (in-floor).
Concerning the insulation *beneath* the PEX, our contractor has quoted us to use a "Reflector Pad" beneath the PEX. I'm concerned this may not be enough and am considering laying down 1" or 2" high-density rigid foam board over top of the gravel BENEATH the concrete altogether.
Can someone illustrate whether my approach is overkill? Would adding a rigid foam barrier between the gravel and concrete be necessary if a reflector pad is already in the plan to be installed beneath the PEX?
I've got one shot at having the floor built properly, and I want to be certain we're doing it right the first time.