Abstract: A building panel system which has a panel to panel connection utilizing opposing male and female joints formed integrally with the external and internal side of structural composite panels. Also, reinforcing splines (32) embedded in the foam between the panel skins. A panel to floor connection utilizes a Z-shaped section (42) with an anchor member (44) embedded into a concrete floor slab or foundation wall. A panel to roof connection uses an angle member (52), trough (56) and shelf (60) joined together with threaded fasteners (38). A panel to roof rail structural connection utilizes the same troughs (56) and inside and outside roof connectors (70) and (72). Thermobreak strips (54) are employed to prevent thermal feedthrough and caulking (40) is used as a vapor barrier in all connections.