A building system using replaceable insulated panels supported by a frame-work. The panels include mated side edges and fastened end edges to form sealed slipping joints. The wall panels are connected to a concrete floor or to floor panels at the base and to roof panels at the top. Both panels, the roof and the floor panels are fixed to the framework to receive and secure the wall panels. Also, the roof panels utilize edging reinforcement to prevent panel delamination and provide supports for installations. The framework is supported with concrete foundations or with movable footings for portable buildings. A combination of slipping joints, and fastening connections of panels to one another and to the framework provide for panel disengagement and replacement of individual panels.