Any building engineers here? Concrete in particular.

[Dino]

I have a new 32x48x14 pole building that is almost ready for the floor. I have 2" thick foam boards that will go down before or after the vapor barrier, I find conflicting information as to what goes where, and a 6" concrete slab. I want radiant heat so I will be running PEX or PERT tubing. My initial plan was to staple them to the foam, but then I'm reading that it's better to have the tubing higher up within the slab. So attach them to a wire mesh? But if the mesh needs to be within the top third of the slab, then the tubing will need to be attached under the wire mesh or the control joints are going to cut right into it. The control joints will need to be at least 1.5" deep so this is tricky. Can anyone make this a little easier? 

[70 sublime]

We are on a farm and built a new milking parlour many years ago
I put the water pipe heated floor in the pit where you stand to milk the cows
We got a big roll of stuff that was like bubble wrap that had a tin foil layer on one side and put that on the gravel base then the wire mesh then tied the pex pipe on top of the mesh
The mesh did not seam to lay perfectly flat so there was no worries that the cement would not seep all the way around it
The floor was not big enough to have to make any cuts in it but was fairly thick and there was no trouble getting the heat to come up

If you put the pipes under the mesh I would be afraid that when they walk around on top of the mesh to pour the cement it would get pushed down and dent the pipe and restrict the water flow