It starts on 12" of #57 stone that makes a 24" x 20" thick footer foundation that the monolithic concrete slab rests on.  The slab is a multi-layered composition consisting of six inches of crushed stone, a 6 mil vapor barrier polyethylene sheet, and five inches of fiber reinforced 3,000 psi concrete.  This Department of Energy design saves Insignificantly on energy (up to 50%) by reducing heat loss to the ground below.  This is important for the pex in floor piping that gives us in floor heating. No cold floor tiles in the winter. The design transforms the floor into what might be thought of as a giant heat sink. The net result is lower utility costs and a more uniform day-to-night house temperature.  Continue....