When the International Code Council last summer finally released its 2007 Supplement to the International Residential Code (IRC), it offered, for the first time, prescriptive guidance for the first time to builders who want to use structural insulated panels (SIPs) for house wall construction. At the time, long-time SIPs professionals welcomed the new guidance as an indicator of growing acceptance of SIPs as a standard building component.

A Panel Pros crew "flies in" a 24-foot R-40 panel for an insulated floor system over an unheated garage in New Hampshire. Able to span 12 feet with a 10-inch panel, SIPs are a no-brainer for insulated floors. But so far the prescriptive SIP code does not mention that use.
Ted Cushman A Panel Pros crew "flies in" a 24-foot R-40 panel for an insulated floor system over an unheated garage in New Hampshire. Able to span 12 feet with a 10-inch panel, SIPs are a no-brainer for insulated floors. But so far the prescriptive SIP code does not mention that use.

One year after the change, though, builders and engineers say the narrow scope of the new SIPs document limits its significance in their work. Listen to Jim DeStefano (www.destefanoassociates.com), a Connecticut structural engineer and a director of the Structural Insulated Panel Association (www.sips.org), who’s familiar with SIPs in timber-frame construction as well as for buildings designed for wind resistance in tough coastal high-hazard wind zones.

He, like others, is happy to see SIPs acknowledged as an “acceptable building system,” but beyond that, he doesn’t see a lot of direct value from the change. As a prescriptive building code, DeStefano points out, the IRC is written to enable builders without formal education in engineering or architecture to design simple building components by pulling values out of tables.

“The reality is that SIPs don’t lend themselves to that kind of use,” the engineer says. “Builders aren’t buying SIPs as items off the shelf to stick into their buildings; SIPS are being sold by SIP contractors who have trained design people on-staff who are capable of designing these building systems, so you don’t need these very simplistic provisions that are in the code.”

The scope of the new code provisions is “extremely narrow,” says DeStefano. “It's limited to just wall panels (4- and 6-inch thickness) and wall heights up to 10 feet high. It doesn't cover roof panels. It doesn't cover high wind-load regions. It doesn't cover high seismic regions. It doesn't cover cases where you have large window openings or unusual panel configurations. And to be quite honest, not many SIP houses we work on fit within those narrow parameters.”

Jim LeRoy, owner of Panel Pros, a New Hampshire-based company (www.panelpros.com) that fabricates panel building packages and erects buildings over the Northeast, concurs. As a 25-year veteran of SIP construction, he says the new prescriptive code “won’t affect me in the slightest.” The InsulSpan panels LeRoy uses (www.insulspan.com), and the assembly methods approved for them, are backed by extensive engineering and testing, he explains, and the business owner can use those methods to achieve more than he could with any prescriptive table.

“If an architect designed a building to the prescriptive method and sent it to us, we would immediately call him back up and say, ‘Look, with our SIPs we can do better’--span farther, and so forth,” LeRoy says. “The prescriptive method is really a step down from what we can really build with the SIPs.” Although it’s tricky to achieve, LeRoy says, SIP construction can comply even with requirements imposed on commercial buildings, where he describes the rules as “out of control.” “We used to just have gravity loads to manage in New England,” he says. “Now with the new wind-load requirements, these buildings could be constructed on the San Andreas Fault.”

But these days, LeRoy says, he finds a ready market for SIPs, which are popular in green building circles, in spite of the need for an engineer’s stamp on any ambitious designs. With the growth of the green building market, he says, the commercial construction world in particular is opening new opportunities for his company even as residential construction lags, despite engineering requirements that LeRoy describes as “out of control.” “The general state of the economy is tough,” he acknowledges, “but the buildings that are being built are being built with energy in mind. And if they're going to be smart about it, they're going to at least take a look at us. So we're bidding a lot of jobs.”

Panel Pros’ experience bears out the widely held view that green construction is a bright spot in the general economic gloom. “It’s still early in the year to make any prediction,” says LeRoy. “I don't know how many of those jobs will actually get built. I’m still holding my breath. But we're on a pace this year to match at least last year, if not better it, for total sales.”

For a downloadable PDF version of the 2007 IRC code supplement for SIPs, see www.sips.org/content/index.cfm?pageId=195.

Ted Cushman is a contributing editor to BUILDER magazine.