However, before specifying SIPs on their projects, designers should consider several erection and performance issues. While SIPA estimates that a construction team familiar with the system can erect a project in half the time it takes to put up a stick-framed building, workers unfamiliar with the system may be slower. “If this is the first time you’re going to erect with SIPs, there is a learning curve,” Hodgson says. “It adjusts the way trades work—you’re not bringing in a person to cut holes through studs, because the chases are already there. There’s no insulation application.”
In addition, project design teams must take extra measures to manage air quality and moisture levels in a SIP building. The highly insulated and tight envelope creates an interior condition similar to that of a walk-in cooler; while the enclosure will maintain constant temperatures well, it also needs a robust air-exchange system to keep the atmosphere fresh and reasonably dry. For this reason, SIPA recommends that designers work with qualified HVAC professionals to ensure that the used air—which can contain moisture, fumes from adhesives, and particulates—is exhausted properly during occupancy.
The reasons for specifying SIPs and the benefits for designing and constructing with SIPs can vary widely, as the following three projects illustrate.
San Luis National Wildlife Refuge Complex
Located in the northern San Joaquin Valley in a vast tract of wilderness outside Los Banos, Calif., the U.S. Fish and Wildlife Service’s (USFWS) San Luis National Wildlife Refuge Complex encompasses nearly 45,000 acres of wetlands, grasslands, and riparian habitats, as well as more than 90,000 acres of conservation easements on private lands for the protection and benefit of wildlife. The USFWS wanted to build a new visitors center for the refuge as well as relocate its existing office nearby to the preserve. The agency hired Arizona firm Catalyst Architecture to design the nearly 17,000-square-foot facility, which the agency required to target net-zero energy and LEED Platinum certification.
Catalyst employed a 55-kilowatt, roof-mounted photovoltaic array that—when used in combination with passive solar measures, strategic use of natural light, energy-efficient mechanical systems, and LED task lighting—delivered a building that goes beyond net-zero energy into net-positive territory by returning more energy to the grid than it consumes.
The project features 12-inch-thick SIPs for the exterior walls and 8-inch-thick SIPs for the flat and sloped roofs. Each panel comprises 7/16-inch OSB facers sandwiching EPS foam. The resulting building envelope achieves an insulation value of R30, which helped the project meet its sustainability target. Catalyst clad some portions of the envelope with weathering steel panels and others with plaster on lathing backed with felt to prevent water infiltration.
The use of SIPs on the project did not come without its complications. In order to open up the facility to views of the wildlife conservation areas, the architects had to orient the building on a north–south axis. As a result, the building’s east and west elevations are the longest, a less-than-ideal orientation for controlling solar heat gain. To solve this problem, the designers minimized the amount of glazing on those walls, which are topped with north-facing roof monitors to bring ample indirect natural light into the interior. Not coincidentally, the sloped surfaces of the roof monitors create an ideal south-facing platform for photovoltaic arrays.
The serrated building profile posed problems for the SIP construction. The facility’s wall and roof monitors created extra on-site sizing and customization that essentially negated potential efficiencies in erection time. “What we’ve learned from working with SIPs is that you want to eliminate or reduce the number of jigs and jogs in the envelope,” says Catalyst partner Matthew Ackerman, AIA. “In our experience, they’re more suited for boxier buildings.”