We are planning a retirement house and would like to use radianting heat. The house will be built on grade and we were planning to use an 4" structural slab, followed by 2" of insullation, and then the radiant heat slab (a 4" concrete slab containing the radiant heating coils. We are concerned that the repeated heating and cooling will crack the concrete and damage the cooling system. Is this an issue we should be concerned about and are there specific steps that should be taken to eliminate the potential problem? Thanks for your comments.