On 4/21/2015 2:24 PM, Robert Green wrote:
"Ed Pawlowski" wrote in message

If you really want to do the job right, you'd put a couple of inches of
foam board under the concrete.


FWIW, I really doubt if foam is necessary because heat rises and even
heating the soil below will eventually cause the surface to become warmer.

Hot air is less dense than cold air so it rises. Heat (energy) travels
in every direction where there is less heat seeking equilibrium.
Foam will make a huge difference. The frost line here is 48" so that
means enough heat is lost for it to freeze. The ground will try to
absorb enough heat to replace that loss. That can be very expensive.