We used 6-1/2-inch-thick R-38 wall panels and 8-1/4-inch-thick R-50 roof panels from Georgia-based SIPS Team USA (229/246-8880, sipsteamusa.com). The panel design is rated for 140 mph winds, and with this much insulation we expect that the church will use 35 percent less energy to heat and cool than if it had been built to simply meet local codes. Because this was our first SIPs project, we opted to hire a SIPs installation trainer from the manufacturer, who supplied both his expertise and a pair of lifting devices.
The T&G-style wall panels have EPS foam cores and 7/16-inch-thick OSB skins on both faces and range in size from 8 feet by 2 feet to 8 feet by 24 feet. They connect by way of 2-by full-width LVL or sawn-lumber splines, which fit into 3/4-inch-deep recesses in adjacent panels’ edges (see slideshow). We oriented panels both vertically and horizontally, depending on door and window openings and wall sizes. According to the manufacturer, each SIP acts as a shear panel, and screwing and gluing them together creates an assembly that acts as a single diaphragm to resist lateral seismic and wind loads. This was a key factor in our decision to use SIPs, since it would have been difficult to cost-effectively add stick-framed walls with similar shear and uplift resistance to the building shell.
Before setting the first wall panel in place, we applied plenty of low-VOC adhesive to the glulam and laminated arch framing. Then we nailed through the OSB skins into the glulams 6 inches on-center in a staggered pattern on both sides, creating an uplift-resistant connection between the panel, glulam, and foundation. The panels are fastened to the arch framing with Trufast 1/4-inch by 8-inch structural screws supplied by the SIP manufacturer. As we set each subsequent panel, we also glued and nailed the spline connections between the panels with the same 6-inch on-center staggered pattern.
To reinforce the 16-foot-tall sanctuary walls to meet local wind-code requirements, we installed flitch beam stiffeners on both sides of each window. The stiffeners consist of three 1-3/4-inch by 5-1/2-inch by 16-foot LVLs sandwiched around a pair of 1/2-inch by 5-inch by 16-foot steel plates; each one weighs 650 pounds. We bolted them to the glulams with 1-inch-diameter bolts, then glued and nailed the SIPs to the stiffeners.
At the top of the eaves walls, the panels are beveled to match the 12/12 roof pitch, and the foam is recessed 3 inches to accommodate a double 2-by top plate. The panels were shipped with one 2-by plate already installed; after all of the wall panels were in place, we installed the second continuous beveled 2-by top plate, gluing and nailing it to both the 2-by underneath and the OSB skins, and staggering the panel joints by a minimum of 4 feet. We also screwed down through the continuous top plate into each wall stiffener with four 8-inch-long Trufast screws.