Baker conceded that, from a strictly materials standpoint, SIPs can be more expensive to install than stick framing. The 2012 code calls for six- to eight-inch SIPs for walls and 10- to 12-inch SIPs for roofs. “Greater thickness translates into higher costs.” He also pointed to the two Zebra Alliance Research Homes in Kentucky, whose thermal performance is being monitored by the Oak Ridge National Laboratory. One of the houses was built using optimal value framing, the other with six-inch SIPs. The SIPs home cost between $8,000 and $10,000 more. But it also saves 21% more energy and attained 40% greater air tightness. Perhaps even more important to builders in the audience, the envelope of the SIPs house went up in five days, compared to 15 for the stick-framed house.
Baker noted that a recent R.S. Means “time and motion” study found that using SIPs can cut framing labor costs by as much as 55% over stick framing, and 11% on electrical rough-ins.
Baker isn’t a fan of prescribing how builders achieve energy efficiency in their construction; he much prefers the “performance” method that measures the end result and pays less attention to how it’s achieved. This performance method, he said, is more likely to take a whole-house approach to energy efficiency than might a prescriptive method that measures each component’s efficiency individually. “Whole-house modeling also sometimes requires thinner panels and takes into account air infiltration,” he said.
He argued, too, that houses built with advanced building systems are less wasteful than stick-built construction, and often require smaller HVAC systems and shorter ductwork runs.
Ferrier lent his practical experience to Baker’s thesis when he noted that SIPs have become part of his marketing arsenal aimed at his two primary customer groups—retiring baby boomers and young professionals—who “are either looking for cost savings or green.”
He showed the audience some of the construction methods he’s used to reduce air infiltration, which mostly emphasize sealing before installation. Ferrier has found that SIPs work better on gable roofs than conventional plywood-and-truss construction because the cuts are more precise and easier to seal. It’s been his experience that SIPs are four to six times stronger than conventional stick-built walls, and are more adaptable to architectural designs, especially when it comes to window cutouts.
Ferrier was quick to note, however, that a given market’s labor costs will ultimately determine the relative cost benefits of using SIPs. He also noted that any efficiency measurement of advanced building systems is likely to depend on the orientation of the house to the sun, as well as the house’s air tightness and insulation. “These are the bases of our efficient homes,” he said.
Posted with permission from Hanley Wood, LLC. Originally posted on Builderonline.com by John Caulfield on February 20, 2012 at http://www.builderonline.com/energy-efficientconstruction/tougher-energy-codes-push-framing-forward.aspx