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| Design teams can readily incorporate SIPs into any low-rise building design, saving the project time and money. |
In the fall of 2008, Western Wyoming Community College, Rock Springs, Wyo., opened the tallest self-supporting SIPs structure built in the United States—the four-story Wind River Hall. The 28,000-square-foot residence hall includes 48 bedrooms and six fully functional kitchens, as well as three spacious living rooms per floor. The project team of BKV Group, Minneapolis; Apex Engineering, Bozeman, Mont.; and Kamerman Construction, Manhattan, Mont., used SIPs manufactured by Premier Building Systems of Fife, Wash., for the building’s exterior and interior walls and roof.
Structural issues
When SIPs are used as walls, roofs, and floors, they provide exceptional axial, transverse, racking, and diaphragm capacities. The wood panel skins and rigid foam core work together to achieve high strength in a manner comparable to other pre-manufactured structural systems, such as I-joists or trusses.
Given their strength, SIPs work well in multi-story, low-rise buildings, such as the Wind River Hall. They make it simple for designers and engineers to specify the panels in place of stick-built construction, including use as shear walls.
As with other wood-framed construction, the practical limit on building height for SIPs comes from the fire restrictions imposed by Type V construction, more so than load bearing capability. To allow the four-story height, the designers incorporated one-hour fire-rated construction throughout the building—including two layers of dry wall—and automatic fire sprinklers.
The team constructed the exterior walls from 6-inch-thick SIPs ranging in size from 4-foot-by-10-foot to 8-foot-by-16-foot panels. As an indication of their strength, the 8-foot-tall wall panels have a capacity of 4,250 pounds per linear foot (plf). Interior walls used 4-inch-thick, 8-foot-by-10-foot SIPs, and the roof used 12-inch-thick SIPs ranging from 4 feet by 12 feet to 8 feet by 24 feet in size. The floors used traditional framing methods.
Two structural challenges with the Wind River Hall included the high gravity loads placed on the lower floors given the building’s height and the two layers of drywall throughout; and, the high shear force from the fierce Wyoming winds. To address these needs, the project team provided lumber columns between the SIPs, hold-down fasteners that provided a load path all the way through to the foundation, and strapping.
Faster construction—SIP construction dramatically reduces the time needed to dry-in a building since contractors can install entire wall, roof, and floor sections at one time. "Anything you build with SIPs goes up faster," said the Wind River Hall general contractor, Glen Kamerman, partner with Kamerman Construction. "You basically do the framing and insulation in one step, which in this project reduced the construction time by two to three weeks or more. The whole building went together really well considering it was a new height for SIPs construction."
Energy savings—The Premier Building Systems SIPs used in the project provide exceptional energy efficiency compared with stick-built construction. The insulating foam is continuous across the panels, unlike fiberglass batts or blown-in or spray insulation that typically leave gaps near framing members.
Because the panels perform as an integrated system, a SIP with a given R-value provides better insulation than higher R-value fiberglass insulation. The U.S. Department of Energy’s Oak Ridge National Laboratory found that an R-14 whole-wall value 4.5-inch SIP wall outperformed a 2x6 wall with R-19 fiberglass insulation. The lab also concluded that SIPs help reduce a building’s annual energy costs by 50 to 60 percent compared with more common framing methods.
Kamerman reported that the college has been pleased with the building’s energy performance—a key consideration given the harsh Rocky Mountain winters prevalent in Rock Springs, which is located at 6,400 feet above sea level.
Improved indoor air quality—The U.S. Environmental Protection Agency lists poor indoor air quality as a top environmental threat to our country, a problem that is often overlooked during design and construction.
A key way to improve indoor air quality is to create a tight building envelope. SIPs enable airtight construction, reducing air transfer and sealing out common pollutants such as radon, molds, pollen, volatile organic compounds, lead dust, and asbestos.
Reduced construction waste—Stick-built construction generates thousands of pounds of scrap as contractors cut stock framing members to length. By comparison, manufacturers produce SIPs in a carefully controlled setting that allows for more precise material management than is possible on a job site. Kamerman estimated for this project that SIPs reduced total construction waste by approximately 20 percent. Depending on the building, SIPs can reduce jobsite waste from the framing alone by as much as 60 percent.
Given the many environmental advantages, building professionals can use SIPs to earn as many as 23 points under the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) for New Construction Rating System.
Joe Pasma, P.E., is the technical manager for Premier Building Systems. He can be reached at 800-275-7086. For more information, visit www.pbssips.com.
