Superior Walls of America's Xi Plus walls feature Dow Thermax reinforced polyisocyanurate insulation covering rigid foam insulation and a 4-in. insulated footer beam. A 4-in. standard floor slab may be poured equal to the height of the footer beam, eliminating the need for an additional screed board. The precast concrete wall panels have a built-in insulation value of R-21.3 and can be insulated up to R-42+.