When a Zero on the Report Card Is Good
- By James Hodgson
- April 1st, 2011
School districts in the United States typically spend more on energy than they do on computers and textbooks combined, according to the U.S. Department of Energy (DOE). The agency reports that “as much as 30 percent of a district’s total energy is used inefficiently or unnecessarily,” and that “the least efficient schools use three times more energy than the best energy performers.”
In light of tight capital and operating budgets, more districts are aggressively pursuing ways to reduce energy consumption in their new schools. Because heating and cooling is a primary driver of energy use, many project teams are focusing on ways to improve the building envelope’s thermal performance.
To this end, a number of districts are moving beyond traditional construction methods such as concrete block, stick framing and steel framing to use advanced materials like structural insulated panels (SIPs). By creating a tight, well-insulated building envelope, SIPs can help schools meet stringent energy efficiency goals, including supporting net-zero energy construction.
SIPs in Short
SIPs are large, single-piece building components made of an insulating foam core (frequently expanded polystyrene – EPS) covered by “skins” of oriented strand board (OSB) or other structural materials. Construction-grade adhesives bond the skins and core together for an engineered system capable of carrying high loads. Depending on the application, additional structural support frequently is not necessary. The model building codes — including the International Building Code (IBC) — recognize SIPs for multiple applications. School designers typically use the panels for exterior walls and roofs, although they also work well for interior walls and some types of floors.
Architects and contractors have used SIPs for several decades in a range of institutional, commercial and residential buildings, including K-12 schools and a host of other educational facilities. SIP manufacturers can configure the panels for use in virtually any architectural design, and the finished buildings look no different on the inside or outside than other construction methods.
While energy savings is a key driver of the growing interest in SIPs construction, some school districts also specify the panels because they install fast. Contractors can assemble entire wall sections in a matter of hours or days. Pre-cut electrical chases eliminate the need to drill holes for wires through numerous individual studs. Manufacturers can also produce the panels with window and door openings to further speed construction. One school in Nevada used SIPs to cut its framing schedule from a planned 121 days to 47 days total — a 60-percent reduction. In that time, the contractor was able to install 2,250 panels within 118,000 square feet of walls and roofs.
High-Performance Building Envelope
In addition to rapid installation, the architects for the 900-student Jacob E. Manch Elementary School in Las Vegas said that the school’s SIP walls and roof provide thermal performance like “a big refrigerator box” — important for blocking searing heat from the desert during the day. Similar to a refrigerator’s shell, SIPs have tight construction with few air leaks, little thermal bridging and uninterrupted insulation.
SIP panels come in large sizes up to eight by 24 feet, so there are fewer gaps within wall and roof assemblies than with other structural systems. In addition, the joints between panels and other parts of the building are usually smooth and even, allowing contractors to readily seal them with SIP tape and mastics. DOE tests demonstrate that SIP construction is up to 15 times more airtight than conventional wall-stud framing with fiberglass batt insulation.
SIP walls and roofs typically also do not have framing members embedded within them, so there is little thermal bridging through studs and joists as with typical stick framing. Further, the insulating foam core is continuous throughout each panel’s height, width and depth.
These factors combine to provide high R-values for SIP construction. The panels have approximately 47-percent higher R-values than stick framing of similar thickness, according to DOE research. Specifically, a 3-1/2-inch-thick foam core SIP wall was rated at R-14.1 versus R-9.6 for 2-by-4 inch studs at 16-inches-on-center with fiberglass insulation.
“Using SIPs cuts down on energy-related costs two ways,” says Gary Radzat, SIP consultant for the Manch School. “There’s less demand for heating and cooling, so HVAC systems can be substantially smaller, saving on equipment costs. Plus, the ongoing costs to run the equipment are much less.” The school’s project team predicted that the HVAC operating costs would be approximately 65 to 70 percent lower than for other schools in the Las Vegas area.
“The energy consultants told us that the cycling of the air conditioning units will be reduced substantially, thereby increasing the life of the equipment by about 75 percent,” adds Radzat. The result is lower upfront capital costs, as well as reduced operating and maintenance costs.
Hot, Cold, Wet or Dry
Design and building professionals have used SIPs successfully for public and private schools in a range of climates, from Arizona to Alaska. In New Mexico, for example, architects specified the panels for the walls and roof of the new, two-story, 18,000-square-foot Zuni Christian Mission School near Gallup.
“New Mexico’s high-elevation desert climate with its extreme temperature swings throughout the day and across the seasons makes it essential to have a tight building shell to achieve energy efficiency,” says architect Larry Hibbard of Hibbard Architecture and Planning. “It was an important criteria of the school’s building committee to minimize energy costs, use resources responsibly, conserve water and remain true to the Zuni Indians’ pueblo design and environmental values, while still staying within a limited budget. The structural insulated panels combined with the steel frame construction provide a creative way to meet these goals. In addition, the construction of the system is not weather dependent and can be erected and enclosed in a minimal amount of time.”
The project team for a new 120,000-square-foot, net-zero energy ready school now under construction in the Seattle area also specified SIPs given the ability of the panels to create a tight building envelope. The new Finn Hill Junior High School in Kirkland, Wash., is designed to be 47 percent more energy efficient than targets set under the DOE ENERGYSTAR program. Compared to existing Seattle area schools, it will be approximately 70 percent more energy efficient.
“Every aspect of the design and construction must be considered in an integrated way when energy conservation goals are so ambitious,” says Anjali Grant, project architect for Mahlum Architects — the Finn Hill project’s designers.
“Utilizing SIP panels not only supported the strategies for energy savings, it allowed for a smooth and rapid assembly process, shaving weeks off a tight construction schedule,” adds Mitch Kent, project manager with Mahlum.
In addition to six-inch-thick SIP walls, 10-inch-thick SIP roof panels and other energy saving features, the Finn Hill Junior High design allows for the potential to incorporate roof-mounted solar panels sufficient to power the school’s energy needs. The SIPs will help reduce the anticipated energy consumption to a point that solar power becomes feasible — even in overcast Seattle.
Another school project in the city used SIPs as the structural support for a vegetated, living roof and to provide superior insulation. The Bertschi School recently opened a new science wing that the project team anticipates will be the first building in Washington State certified to the stringent Living Building standard. The wing includes solar panels to produce all of the energy needs of the new space, along with natural ventilation, radiant floor heating and various other green features.
A Big, Fat Zero on the Energy Bill
Affordable, net-zero energy construction for schools and other buildings is possible with today’s technologies. Structural insulated panels can play a significant role in reducing heating and cooling energy consumption, and work best as part of an integrated, whole-building approach. The DOE-sponsored Commercial Buildings Consortium sums this point up well in a February 2011 report: “Major strides in reducing energy use will not be achieved unless integrated design becomes a standard practice…. As building systems become increasingly complex, optimizing their interactions and understanding the performance of a building from a holistic perspective is paramount.”
James Hodgson is the general manager for Premier SIPs by Insulfoam. He can be reached at 800/275-7086 or www.premiersips.com.