Structural insulated panels (SIPs) have been around for more than half a century, but despite their many benefits, they hovered at the far edges of the building industry for decades. With the recent interest in green building and energy efficiency, though, they have gained popularity as a viable alternative to stick-built framing.
Consolidating framing, insulation, and sheathing into one installation step, SIPs are primarily constructed with two outer skins of OSB laminated to an insulating foam core of either expanded polystyrene or polyisocyanurate. A study by Oak Ridge National Labs has shown that SIPs provide a more energy-efficient and airtight structure than stick framing because they create a wall with continuous R-value; wall studs create a thermal break, counteracting the effects of batt and even foam insulation.
“SIPs are typically 40 to 60 percent more energy efficient than stick construction,” says Damian Pataluna, president of FischerSIPS LLC, adding that tested structural strength, efficient use of natural resources, warranties, and reduced cost of labor add to their appeal.
The panels are factory-built, some supplied as blanks with no cut-outs, others with window and door openings designed into the panel and with electrical chases routed, reducing waste on the jobsite. Most manufacturers offer ready-to-assemble systems that require no on-site cutting.
Once blueprints or drawings are submitted, the manufacturer analyzes the plans to determine optimal layout of the panels for each building, places window and door cut-outs, and identifies electrical chases.
Manufacturers such as Winterpanel, Agriboard, Insulspan, Premier Building Systems, Precision Panel, W.A. Brown, FischerSIPs, and many others offer full plan design, panel engineering, and manufacture of structural insulated panels for custom homes and some even will handle installation.
Panels can be shipped sorted in the sequence in which they will be installed, but sometimes it is more cost effective to ship them in random sequence and sort them on the jobsite. Each panel is identified, and drawings and instructions for assembly are provided. Depending on the complexity of the building design, a SIP home can usually be framed in days, instead of the weeks stick-framing requires. However, interior walls still must be stick-built.
Although the panels come in standard sizes they are built to fit each individual home plan, and custom design capabilities are extensive. “If you've got the right builder and the right SIP manufacturer, just about anything can be done,” says Neal Wilkinson, structural product manager for WA Brown, maker of the SIPTEX system. Some SIP manufacturers can create features such as curved walls and roof turret treatments.
However, when it comes to complex roof designs, SIPs can be limiting. “The more intricate the roof lines and wall elevations—the more extravagant with lines and angles and cuts that have to be made—the less efficient the use of SIPs becomes,” says Tim Evans, vice president of sales and marketing for Agriboard. Roof panels also have span limitations, according to Doug Anderson, sales manager for Winterpanel.
Planning appropriately is the key to successfully building with SIPs. Builders and owners must understand that making on-site plan changes to a SIP-built house is more difficult and takes more time than making changes to a stick-framed house; it can be done, manufacturers say, but not as easily.
Awareness of lead times is also important. “When you start thinking about using SIPs, you want to get in contact with the manufacturer to find out what their lead times are so you're not caught by surprise,” Pataluna advises. “I tell my customers they need to have their SIPs ordered by the time they start breaking ground.”