Structural Insulated Panels (SIPs)

Article and photos by Gregory Havel

Structural insulated panels (SIPs) (photo 1) are advertised as energy-efficient, strong, and cost-effective. In some parts of North America, houses, apartment buildings, and even commercial structures are constructed of these panels, including exterior and load-bearing walls and roofs. In other parts of North America, these panels are used for roofs that are supported by other types of construction. 

(1)

A structural insulated panel is simply a block of foam insulation board (usually fire retardant-treated) glued between two sheets of oriented strand board (OSB) using a waterproof construction adhesive. SIPs are usually manufactured four feet wide and in eight-foot or 12-foot lengths, corresponding to the common sizes of OSB sheets. 

The edges of load-bearing SIPs for use in walls (photo 1) are usually manufactured so that a single or double stud of 2×6 or 2×8 lumber will fit tightly between the two sheets of OSB and against the edge of the foam insulation. The two SIPs are butted together on the single or double stud and attached with a waterproof construction adhesive/sealant and nails. Multistory buildings are constructed by building a floor platform on top of the SIPs wall and adding SIPs for the second-floor walls. Window and door openings may be provided in panels at the factory or may be cut at the construction site.

(2) 

The edges of SIPs used as roof panels (photo 2) and as nonload-bearing walls are often manufactured so that splines of nominal 1-inch lumber are used to join the panels on both faces, on all four edges. The splines are inserted with waterproof construction adhesive and nailed through the OSB faces of the panels. The splines are laid out so that the ends of the splines are offset from the edges of the SIPs.

 

Interior partitions inside structures built of SIPs are often conventional wood-stud framing covered with gypsum drywall board.

 

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The room side of SIPs is usually finished with gypsum drywall board on furring strips screwed to the SIPs. This provides a concealed space (photo 3) for electrical and data cables and plumbing and heating pipes. Cutting into SIPS to embed cables and pipes will greatly reduce their strength and is not permitted. Drilling through SIPs for pipes and cables is acceptable and may require a foam sealant between the pipe or cable and the OSB. 

The exterior of a building constructed of SIPs can be finished like any wood-frame building: combustible (wood or plastic) or noncombustible (metal or cement-board) siding, masonry (stone or brick) veneer, or other materials.

 

SIPs are not inherently fire resistive. Tests by manufacturers have shown that under fire conditions, SIPS will burn like their component materials: wood (OSB) and plastic (foam insulation and adhesives). Laboratory testing of assemblies of SIPS protected by Type X gypsum wallboard can achieve ½- and 1-hour ratings, using the test methods described in NFPA 251 (ASTM E-119, UL 263),
Methods of Tests of Fire Resistance of Building Construction and Materials. The results of these tests will be included in the fire resistance reports of the lab conducting the tests and will not appear in Underwriters Laboratories’
Certifications Directory of Fire Resistance Ratings (
http://database.ul.com; search for “BXUV”) unless UL did the testing.  

Visit the Web sites of the Structural Insulated Panel Association www.sips.org, and manufacturers for details on the manufacture, fire resistance testing, and proper installation of SIPs. 

Gregory Havel is a member of the Burlington (WI) Fire Department; a retired deputy chief and training officer; and a 30-year veteran of the fire service. He is a Wisconsin-certified fire instructor II and fire officer II, an adjunct instructor in fire service programs at Gateway Technical College, and safety director for Scherrer Construction Co., Inc. Havel has a bachelor’s degree from St. Norbert College; has more than 30 years of experience in facilities management and building construction; and has presented classes at FDIC.

 

 

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Subjects: Building construction for firefighters