The design of Styrofoam Wallmate insulation was the answer to the perennial demand for a simple way to insulate and finish basement space. The manufacturer put a 3/4-inch-deep by 11/2-inch-wide rabbet along each long edge of a 2x8 piece of 11/2-inch-thick extruded polystyrene board. When two sheets are butted together, the rabbets form a 3-inch-wide vertical channel. When used to insulate an entire wall, the rabbets form a series of 2-foot on-center channels that are just big enough for 1x3 furring strips, which can then be fastened through the insulation and into the wall with Tapcontype screws. The furring strips hold the insulation in place and act as a screw base for drywall. Wallmate has an R-value of R-7.5 and
