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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