What is the foam/pex thing gonna be? A swimming pool or a pond? I couldn't find it going back a few pages sorry.
I've enjoyed what I've read on this thread tremendously.
The foam is a combination of 1" foam sheeting plus another inch of sprayed foam which creates an insulation liner between the ground and the concrete which will be poured inside that foam area. It's sort of like a foam lined mold for a concrete slab that my new shop will be built on. The maze of small white tubing on top of the yellow foam will circulate hot water. The entire concrete slab becomes a heating element.
That is how we will heat this new shop in the winter months.
