Many of you who design radiant floor heating systems have probably had the opportunity to watch as the neatly placed tubing circuits are buried in concrete. Sometimes the tubing and reinforcing mesh is lifted into the thickness of the slab as the concrete is placed. Other times, the masons trample over the tubing and mesh as if it wasn't even there. Their adherence to the drawings on your plans and instructions in your specifications seemed less and less urgent as each additional yard of concrete flowed down the chute. As you watched, you probably wondered how the depth of the tubing would affect the thermal performance of the floor.
That is certainly a reasonable question for any radiant system designer to answer. After all, unlike relocating a sensor or trimming the impeller of a pump, there is no chance of changing tubing depth once that screed slides over the concrete. The slab's performance over a very long service life is now fixed.