Abstract: A building side wall construction including a plurality of expanded polystyrene panels placed edge-to-edge and connected by connecting studs each comprising a pair of C-shaped channels fastened in back-to-back relationship with each C-shaped channel being received in complementary mating relationship in grooves of the adjacent panels, and central reinforcing channels received in mating slots at central portions of the panels, with the opposite ends of the connecting studs and the central reinforcing studs being fastened to lower and upper channels in which they are received.