Frame, sheathe, and insulate, all in one step. Thermastructure Building Systems are interlocking, load-bearing composite 4x8 panels made of polystyrene and galvanized steel. With electrical conduits, window and door openings molded in, these custom panels weigh 45 pounds each. Shiplap joints are connected on site. The tight-fitting joints reduce air flow, and the insulation values are higher than for traditional stud systems. The manufacturer, RADVA Corporation, will provide training and assistance in construction. They can customize shapes and sizes and tailor panels to accommodate special wiring, and window and door openings. Contact RADVA Corporation, 604 17th Street, Drawer 2900, 1st Street Station, Radford, VA 24143; 703/731-3717. Dearth Vapor New fiberglass-faced, fiberglassembedded gypsum board gives you a moisture-resistant substrate. Den- Shield panels, available in sizes 4x8 or 4x5,