The ICF construction system produces a solid concrete exterior wall system with a 4”, 6”, 8” or 12” thick, 4,000 PSI steel reinforced concrete slab core.  The concrete slab is surrounded by almost 3” of expanded polystyrene foam (EPS) on both sides.  Sidings of any choice are applied directly to the foam exterior by screws into embedded polymer, or steel in some cases, framing strips, and finishes likewise applied to the inside.  It is, in science sense, a concrete vault that stores BTU’s.  Think of a rock inside four IGLOO coolers, as big as seven concrete trucks in a row, glowing energy.  Think how long it could keep you warm (or cool) at a cool (or warm) time.  It averages the temp the HVAC system battles to the middle of the extremes, then insulates it really good and makes it air tight.