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September 29, 2011
A net-zero energy home or building is one that generates as much power on-site as it consumes over the course of a year. To achieve this, architects specify renewable energy sources such as rooftop solar panels and windmills to generate electricity, and design the building to use energy as efficiently as possible.
Because heating and cooling account for about half of U.S. home and building energy use, a primary way architects reduce energy consumption is with a tight, well-insulated shell. This can be difficult using traditional construction methods such as lumber framing, which have numerous hard-to-seal gaps and cavities. To solve these challenges, design professionals are increasingly turning to structural insulated panels for walls, roofs and floors.
More airtight buildings
SIPs are pre-fabricated components that form a building’s structural frame and have built-in insulation. They are made of two “skins” of oriented strand board an engineered wood panel with strength properties similar to plywood sandwiching a rigid inner foam core. The OSB and foam work together to support loads throughout the building, while the foam insulates against heat gain or loss.
Architects can specify SIPs in large sections up to 8 by 24 feet so fewer gaps need sealing. As a result, SIP buildings are nearly 15 times more airtight than conventional wood-framed buildings, according to the U.S. Department of Energy.
Additionally, the insulation is continuous throughout the height, width and depth of each panel. By comparison, wall studs and roof and floor joists in traditional wood-framed buildings interrupt the insulation every couple of feet. For a similar thickness, SIPs have about 47 percent better insulating capability than wood framing with fiberglass batts.
The air tightness and efficient insulation of SIPs can help reduce a building’s annual energy consumption up to 60 percent, and allow for smaller-size heating and cooling equipment. In conjunction with high-efficiency windows and doors, energy-efficient lighting and appliances, and similar systems, SIPs help lower energy demands to the point that on-site power generation can be sufficient to meet building users’ needs.
Numerous buildings constructed throughout the U.S. over the past 40 years demonstrate the energy efficiency of SIPs. These include single-family homes, apartments, schools, offices, restaurants, medical facilities, places of worship, and other commercial and institutional buildings. In the Pacific Northwest, several recent projects highlight the benefits.
A notable example is the new Finn Hill Junior High in Kirkland. A design team led by Mahlum Architects of Seattle used 6-inch-thick SIP walls and 10-inch-thick SIP roof for the 120,000-square-foot school. The team predicts that the SIPs and other energy-efficient building components will reduce energy consumption an estimated 70 percent compared to older Seattle area schools. Finn Hill’s net-zero energy ready design means the potential area for roof-mounted solar panels would be sufficient to power all the school’s needs.
In Oregon, the architect for Portland Community College’s Newberg Center designed the 12,000-square-foot classroom and conference building also to be net-zero energy ready. The SIPs are part of a range of energy-efficient elements, including rooftop solar panels, radiant concrete floors and systems for natural ventilation and daylight.
“The first and maybe most critical step in getting a building to net-zero energy use is to reduce its energy consumption,” said Doug Reimer, senior project architect for Hennebery Eddy Architects, designers of Newberg Center. “The SIPs are intended to super insulate and reduce air leaks to stabilize the interior environment. Then, fewer photovoltaic panels are required to generate energy to achieve net-zero.”
Saving homeowners money
In addition to commercial and institutional buildings, SIPs are gaining attention in residential construction. Several local homebuilders used SIPs within their award-winning energy-efficient designs. Clifton View Homes of Coupeville received the EnergyValue Housing Awards 2011 Gold Award from the National Association of Home Builders and DOE for a home with SIP walls and roof. Olympia-based builder Scott Homes won a Silver Award for one of its SIP homes.
“Everyone is so amazed by the energy efficiency the SIP panels provide,” said Scott Bergford, owner of Scott Homes. “It only costs an average of $200 to $300 a year to heat one of my homes. That’s anywhere from one-fifth to one-sixth the typical costs for this region, so the savings are pretty significant and the homeowners love that.”
In some cases, homebuilders, homeowners and commercial building owners may be eligible for energy-efficiency tax credits or deductions from using SIPs and other advanced building components. Financial benefits include up to $2,000 for new energy-efficient homes and $1.80 per square foot for new or existing commercial buildings. For information on state, local, utility, and federal incentives and policies that promote renewable energy and energy efficiency, see the Database of State Incentives for Renewables & Efficiency at http://www.dsireusa.org.
Beyond the energy cost savings to building owners and contractors, constructing with SIPs provides broader, long-term environmental benefits. For example, the estimated average energy savings over 50 years for a SIP home in the U.S. is 9.9 times greater than the energy needed to produce and deliver the SIPs compared to traditional stick framing, according to research commissioned by the EPS Molders Association.
In addition to using SIPs to enhance a building’s energy efficiency, project teams often select the panels for their fast and easy installation. SIPs can reduce construction time to allow for earlier building occupancy.
“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,” noted Mitch Kent, Mahlum Architects project manager for Finn Hill Junior High.
Other building teams regularly achieve similar results. For example, contractors for the 70,000-square-foot Jacob E. Manch Elementary School in Las Vegas reduced the project’s framing schedule from 121 days to 47 days using SIPs, a 60 percent time savings. In that time, they were able to install 2,250 wall and roof panels. Across the city, the developer of the four-story, 82-unit Sarann Knight apartment complex erected approximately 100,000 square feet of SIP walls in only 80 days.
“Compared to stick framing, SIP walls go up much faster since they can be installed in large sections and eliminate the need for separate on-site framing and insulation work,” said Sharon Bullock, project manager for Community Development Programs Center of Nevada. “The finished walls are also beautifully straight, which saves time on drywall installation, painting and other finishing work.”
Although traditional wood framing, concrete blocks and other structural systems continue to predominate in the construction industry, interest is growing in advanced components like SIPs. The panels provide a straightforward way to help meet stringent net-zero energy goals driven by owner interest and government regulations.
James Hodgson is the general manager for Premier SIPS by Insulfoam. The Tacoma-based company is North America’s largest structural insulated panel manufacturer.