I have installed in floor pex for hydronic heating. I know I have to insulate under it. Does anyone know if spray foam (not the small cans, but the polyisocyanate large scale mixture used for home insulating) is an acceptable choice? I feel it may crack with the expansion and contraction. Thanks
I dont think the temp difference is wide enough to affect it, your radiant will operate at 110-115f and the floor inside might go from 60 to 115? On exterior walls and attic ceilings that are foamed you can go from winters lows to hotter than 115 for a wall in the sun. A dark wall, flat black, in sun can reach maybe 140f. I would ask the manufacturer of the pipe and do what they say is best. I would paint exposed foam, spray it with latex paint since air oxidises it. UFFI in walls tuened to dust in 10-15 years, sun ruins the foam in a can, so over time it might degrade, very slowly though.
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