There are two unmistakable trends in the home building industry. First, dimensional lumber is losing its place as the dominant structural material. Second, manufactured components are steadily replacing site-built ones. Soon, panelized walls will leap to greater importance. Techbuilt Manufacturing, Inc. is well-positioned for both trends.

Their ThermoTech 21 engineered panels feature 18 ga. steel tubes for strength and expanded polystyrene (EPS) foam for insulation. Wall panels are 7-1/4 in. thick (R-30) and roof panels are 11-1/2 in. thick (R-50). EPS foam is ozone-safe, because it uses air for a blowing agent.

The panels are made by first routing channels for the 1x2 steel tubes. They are placed on opposite sides of the panel every 24-in. Each tube is connected to its mate with a long screw. Foam separates the opposing steel tubes, preventing thermal bridging. In the wall panel, 5-1/4 in. separates the tubes. Four steel angles placed on the top and bottom edges join the steel tubes. These angles can span the ends of adjacent panels to lock them together. Panels can be up 32 ft. long.

A 20 ga. steel angle wraps each corner, and fastens to the tubes. Siding screws directly to the tubes. Window and door openings are built into the panels and wrapped with 2x8 lumber. Roof panels sit on a ridge beam, so the entire upstairs has cathedral ceilings.

The wall panels can be used below grade, too. The panels sit on a standard footing. Treated plywood is attached to the panel and then covered with waterproofing.

With R-30 walls and R-50 roofs, the heating load is about 25 to 30 percent of a wood-framed house, so low that a high-recovery water heater satisfies all water heating and space heating needs. A wiring chase is preformed into the wall panels and electrical boxes attach to the steel tubes. The manufacturer recommends that plumbing be located in interior partitions or in specially-built plumbing chases.

The building system includes a unique feature: minimalist rim joists. Only the top chord of the metal-web floor truss bears on the outside walls. The lower chord hangs entirely inside the panel walls. Instead of a 10- to 12-in. rim joist, the comparable area in the ThermoTech wall is only 1-1/2-in.

According to the manufacturer, component cost is 5 percent more than typical wood-framed construction. Like other panelized systems, higher material cost can be more than offset by lower labor cost. The panels carry a 10-year limited warranty. For further details, please visit the Techbuilt Systems website.