Structural insulated panels (SIPs) have always been easy to assemble into strong, energy-efficient walls. Now, planning and permitting are streamlined, too.
The International Code Council voted to adopt SIPs into the International Residential Code (IRC) in May. Prescriptive specifications and installation details will be included in the 2007 supplement. The upshot: builders using SIP building envelopes in residential projects will no longer be required to conduct additional engineering to show equivalency to the IRC.
The Partnership for Advancing Technology in Housing (PATH); the Structural Insulated Panel Association (SIPA); APA – The Engineered Wood Association; and SIP industry partners developed the prescriptive approach, which requires no guesswork by the builder. The approach explains what SIPs are and exactly how they’re used: “spans, connections, what kind of screws, the nitty gritty details defined,” says Dana Bres, a research engineer with PATH.
“Different manufacturers have different ways of doing things and slightly different products,” says Chris Schwind of SIPA. “By getting the test data from all the manufacturers, we came up with a minimum standard that they all meet. Now it doesn’t matter if one manufacturer does things a little differently from another.”
So builders now have two resources: “The manufacturer of the panels provides technical assistance; the building code provides prescriptive guidelines. The combination of the two allows builders to get it right,” says Bres.
SIPA and the NAHB Research Center surveyed about 900 builders in April and found that roughly half the builders surveyed were familiar with SIPs but haven’t used them. Schwind predicts the code change will attract more builders.
“Having it in the building code is just one more barrier builders don’t have to face when choosing this product.”
It also makes it easier to get to yes with code officials and homeowners, says Bres. However, the immediate effect of the code change will vary depending on location, says Curt Stendel, a SIP builder in Minnesota.
Over the long haul, Stendel predicts it’s making getting building inspectors’ approval easier, but many municipalities are still working under the 2000 version of the IRC.
So if your municipality is still working with an outdated code, be sure to bring the 2007 code (available at www.sips.org) to your building inspectors’ attention.
“Lack of education by the industry is the biggest barrier,” says Stendel. “It’s one-on-one education of inspectors that makes the most difference.”
(Photo: Good planning and teamwork speed SIP construction and provide for a strong, durable energy-efficient home. Photo Courtesy of Curt Stendel, Panelworks Plus.)
Why choose SIPs?
SIP building has increased significantly with the rising popularity of green building. According to SIPA, total SIP production increased 6.1 percent in 2006, which followed a 12.1 percent increase in production in 2005.
“SIPs dramatically reduce the amount of time it takes to frame a building,” says Schwind. “You are working with large prefab sections, you have fewer joints to seal, you can place panels as big as 8 by 24 feet using a boom track or a forklift, and it will reduce the man hours to dry in a home.”
The learning curve is also relatively short. “It takes less skilled labor to put up SIPs to frame a house than wood framing: two to three homes are probably all that’s needed to train a crew,” says Schwind. “Crews can also work faster because walls are perfectly straight. It’s a continuous nailing surface to attach drywall, so it’s easier and faster.”
Labor savings depend on the size and experience of the crew and also on job-site conditions. And you’ll have to pay for a crane to lift the panels. But if you’re setting panels that are already insulated, you don’t have to spend time framing walls or dealing with warped lumber, which saves time and money.
SIPs also produce a lot less waste. Made in a factory to specification, they’re delivered to the site pre-cut and ready to install. This means there’s hardly any job site waste unless someone got the shop drawings wrong. And because the panels go up so quickly and are so big, there’s less job site theft. Who’s going to walk off with 8-foot by 24-foot panels?
With the extra insulation and the tight fit, SIPs also save considerable energy. “SIPs give you the ability to control air infiltration better since there isn’t as much air going in and out,” says Schwind. He notes that because SIPs create a tighter building, ASHRAE standards require you use mechanical ventilation with them to ensure proper indoor air quality.
For builders seeking LEED or Energy Star certification, SIPs are a real bonus, and not only for their insulation and air sealing benefits.
“You can pick up one extra LEED point if the sheathing of your SIPs has an FSC stamp,” says Stendel. (The Forest
Stewardship Council stamp certifies that the wood was sustainability harvested.)
(Photo: Building on an island that doesn't allow access for a boom truck can be a challenge. This SIP installation crew found a way to accomplish the task and form a virtual cross-section of the cabin in the process. Building the shell of a new structure with a complete package including pre-cut panels benefits the environment and the builder's bottom line. Photo Courtesy of Curt Stendel, Panelworks Plus.)
With the recent code change, Energy Star also agreed to waive blower door testing with SIP homes. Inspectors now only have to do a visual inspection, saving the cost of the blower door test.
“For Energy Star builders, this is $300 to $500 they don’t have to spend proving something they already know. This frees up the money for better windows, doors and appliances,” says Bres.
Given all the plusses of SIPs, why, exactly, have builders been slow to adopt them?
Terry Dieken, owner of Extreme Panels in Minnesota and a SIP manufacturer for 14 years, says humans are just creatures of habit. Although SIPs have been around for 40 years, they’re still new to a lot of builders. “I’m old enough to remember when everyone used plaster,” says Dieken. “Then sheetrock came out. Oh, that was a terrible thing. But who uses plaster anymore? Someday, it’ll be the same with SIPs.”
Next on the Horizon
The prescriptive method is for SIP walls only. SIPA and its industry partners will be working to design standards for connecting SIP roofs to insulating concrete form (ICF) walls and to SIP walls next.
This article was first published in Professional Builder, September 2007 and is reprinted with permission.