Cannot control UFH temperature

[kerching]

Well FWIW I was told NOT to use plywood as I has the thermal properties of an open door. I was told to use No More Ply with 2 coats of SBR on each side prior to mat/self level/ioes

but this info only came from the manufacturers of the heatmat so what would they know? Oh, and my system was designed by the owners/chairmans son

my system works a treat