Abstract: A structural insulated panel system including individual panels for forming the floor, walls and roof of a structure. Each panel has an insulative rigid foam core with a rigid foam layer having an overhang extending outwardly beyond the edges of the core. Interior sheathing is placed over the core layer. Exterior sheathing is placed over the outer surface of the core and has an overhang which extends slightly beyond the core edges. Channels are formed around the core edges and receive plates at the top and bottom and transition studs at the side edges. When a structure is assembled with the panels, transition members are placed in the channels along the side edges and are overlapped by the foam layer overhangs and the sheathing overhangs to effectively seal and enclose the structure.