Paraphrasing Benjamin Franklin in “Poor Richard’s Almanac,” “A kilowatt saved is a kilowatt earned.” The centuries-old idea in that cliché summarizes the essential requirement for net-zero energy buildings: saving energy through efficient building design comes before generating additional energy on-site. Although reducing energy consumption is often not as sexy as adding solar panels and wind turbines, it is the first topic to address when designing for net-zero energy.
The U.S. Department of Energy (DOE) lists four key energy-related characteristics of buildings that are largely fixed at construction: aspect ratio, orientation, glazing fraction, and core envelope. Of these, getting the envelope right is especially critical since HVAC demands account for one-third of commercial buildings’ energy use.
Much of the current discussion of net-zero energy buildings is focused on incremental changes to reach goals decades away. For example, DOE’s Net-Zero Energy Commercial Building Initiative calls for such buildings by 2025, the AIA’s 2030 Commitment seeks carbon-neutral projects by 2030 (largely linked to energy use), and the state of California requires all new commercial construction to be net-zero energy by 2030. Fortunately, though, as far as the building envelope is concerned, technologies exist today for high energy efficiency. Among these are structural insulated panels (SIPs).
SIPs, of course, are not new. They have been around for decades, but with the increased focus on green construction, SIPs increasingly are being used instead building methods such as stick framing, and concrete tilt-up.
The key environmental advantage of designing and building with SIPs is their ability to create a tight, high-performance building envelope. The rigid foam core provides continuous insulation across the panels’ width and length, reducing the thermal bridging created by studs.
In comparative testing of SIP construction and stick framing, DOE’s Oak Ridge National Laboratory found that SIPs have a 47 percent higher whole-wall R-value than a typical stud wall. A 3.5-inch-thick core SIP had a whole-wall R-value of 14.09 versus 9.58 for 2-by-4 studs at 16 inches on center with fiberglass batt insulation. Looking at building envelope performance from another angle, the laboratory conducted blower door tests that demonstrated SIP construction is 15 times less leaky than standard wood framing. Because SIPs are manufactured in a controlled environment and are delivered in large-sizes, building with them requires significantly fewer joints to be sealed. The bottom line result is that SIPs can help reduce heating and cooling demands up to 50 percent to 60 percent over conventional construction and allow for installation of smaller HVAC systems.
A recent project underscores SIPs’ role in energy-efficient commercial and institutional buildings. In fall of 2009, the Clark County School District opened the Jacob E. Manch Elementary school, a new 70,000-square-foot facility in Las Vegas built with SIP walls and roofs. The project’s architects estimate that HVAC operating costs will be about 65 percent less than those for other schools in the district. Notably, the SIPs also enabled the contractors to reduce the framing schedule from 121 days to 47 days (a 60 percent time savings) and helped saved about $2 million in total construction costs.
In addition to reducing energy use, SIPs offer several other green building benefits, including supporting indoor air quality and reducing construction waste. The tightness of a SIP envelope makes buildings less prone to infiltration by common pollutants such as radon, molds, pollen, VOCs, lead dust, and asbestos. As such, SIPs can be an important part of creating a healthier indoor environment, whether for homes, apartments, schools, offices or healthcare facilities. Because they are made in a controlled environment, manufacturers are better able to plan material use than is possible on the jobsite. Compared to stick framing, SIP construction can help reduce construction waste by up to two-thirds.
The coming few years will be a key time in the evolution of architecture and building as the focus on energy use drives the rapid development and adoption of more efficient methods. Fortunately, many of the pieces are already in place to achieve net-zero energy construction, and existing systems such as SIPs will likely play a growing role.
James Hodgson is the general manager for Premier Building Systems, an SIP manufacturer in Fife, Wash. pbssips.com