Panels Knock Up to Five Weeks Off Building Schedule
Second-generation Austin, Texas carpenter and small custom builder Fred Ballard says that he doesn’t have to worry about warped walls, mold issues or termites now that he’s using steel structured insulated panels (SIPs).
“The first home we built with SIPs had a 20-foot top plate,” Ballard said in an August case study by the Partnership for Advancing Technology in Housing (PATH). “After a few hours of connecting panels, it was amazing how consistent and absolutely straight the walls were. Even better, they can knock three to five weeks off the framing and insulation stage of construction.”
“Steel SIPs are also able to withstand extreme weather conditions during construction,” he said. “They’re waterproof, which means we build more houses since our construction schedule is less dependent on the seasons. Our homes are engineered to withstand hurricane-force winds, making them safer as well.”
Specializing in residential, multifamily and light commercial projects, Ballard’s company, Blue Horse Building and Design, builds about five homes a year, ranging in price from $650,000 to $1.4 million, and he has built more than 20 homes using steel SIPs since 2001.
SIPs are made from a thick layer of polystyrene or polyurethane foam sandwiched between two layers of oriented strand board, plywood, light-gauge steel studs or fiber cement. The result is an engineered panel that provides structural framing, insulation and exterior sheathing in a solid, one-piece component. Arriving precut to the job site, the panels can be rapidly assembled by workers without extensive training.
A Better Thermal Envelope
SIPs add between 5% to 10% of the overall cost of construction, he says, which can be offset by monthly energy savings of 30% to 50% from the better thermal building envelope the technique provides. The investment in steel SIP construction is usually recouped within a 10-year period, he says.
Steel SIPs can be used for floors, interior and exterior walls, ceilings and roofs, according to PATH. Manufacturers of steel SIPs usually produce specific widths, so designing with modular increments corresponding to stock panel widths is recommended. Stock panels are typically 4 feet wide and range from 8 to 12 feet high. Even if the panels are cut to fit one wall, the remaining portion can usually be used in another location to minimize waste.
Ballard uses TransconSteel UltraFrame panels that are made with Delta Studs, a patented lightweight steel framing system with the same geometric profile as conventional steel stud C-channels. A moisture-cured adhesive is then used to glue expanded polystyrene foam between the Delta Studs. The foam has a fire retardant built into its cellular structure and also includes a Borate treatment to keep pests from nesting in the walls.
The panels come in thicknesses of 3-1/2 and 5-1/2 inches with light gauge (24 ga.) Delta Studs at either 16 inches or 24 inches on center, he said. He uses both thicknesses, but leans more to the thicker panels “to create a more satisfying-looking wall with deeper window jambs and increased sound attenuation.”
As Easy as Building With Legos
“We prefer SIPs with pre-cut openings, which include headers and require accurate door and window measurements to minimize cut-out waste,” he said. “The alternative is to field cut openings and deal with the extra waste. Even with precut panels, unforeseen plan changes are accommodated fairly easily. There’s nothing that can happen in the field that’s unfixable.”
Ballard said he sometimes orders a few extra panels because if the need for an additional panel arises it won’t be available at a typical home improvement store and could cause a delay.
Most SIPs weigh between 30 and 80 pounds, requiring only two men to position them, and Ballard usually has three to five crew members on site to install the panels. “As long as your crew knows square, level and plumb, they can install the panels just fine,” he said. “A typical house, around 2,000 square feet, takes about three to four days to get the SIP walls and roof up.”
“As with any home, but even more so when using SIPs, it’s really important to make sure that the slab is formed and poured properly to ensure straight edges and a level finished surface,” he said. “We measure the slab, lay the bottom track out, much the same way we would lay out a bottom plate for a wood-framed wall, and then use the anchor bolts to attach the track to the slab shortly after the concrete has set up.
“I like to hang the track off the slab 1/2 inch to create a drip ledge even though we also have seal underneath the track. Once the bottom track is set in place, we start at a building corner and set two corner panels into the track, joining them with a sealing caulk adhesive before fastening them together. It’s almost like building with Legos — it’s truly that easy.
Most SIPs have chases already pre-made for electrical and plumbing, and training trades usually involves a brief explanation, said Ballard.
“On interior wall surfaces, standard gypsum board can be attached directly to panels containing electrical and plumbing chases,” he said. “Otherwise, drywall is attached to the hat channels on furred walls and finished with conventional tape and mud. We frame interior partition walls conventionally with either finger-jointed wood studs or light-gauge steel and insulated with either fiberglass batts or spray-applied foam. For fireplaces and chimney shafts, we use Isokern systems that ate modular masonry units made from volcanic pumice that can be installed in under a day.”