Building With Structural Insulated Panels
By James Hodgson
Building professionals are increasingly using structural insulated panels (SIPs) for their contribution to green building goals. These include up to 58 percent energy savings and improved indoor air quality from a tighter building envelope, and reduced jobsite construction waste generated by cutting individual boards and other materials on-site.
By developing expertise in advanced building methods such as SIPs, contractors can differentiate themselves from the competition and be better positioned to tap into the growing green building market.
Building with SIPs is not complicated—and offers a number of construction efficiencies compared to other building methods—but does require specific knowledge that differs from stick framing, concrete block, and steel.
SIP APPLICATIONS
Nearly any type of low-rise building can be constructed with structural insulated panels. Structures up to four stories tall have successfully used SIPs, as have buildings in hot, cold, wet, and dry climates. Typical applications include schools, lodging, offices, retail, community centers, industrial facilities, and churches, as well as homes and apartments.
SIPs are high-performance, engineered wall, roof, and floor components composed of two outer sheathing layers (skins) laminated to a rigid insulating foam core. Oriented strand board (OSB) skins and expanded polystyrene (EPS) foam cores are the most common materials used.
The skins and foam core work together to achieve high strength in a manner comparable to other engineered structural components such as wood I-joists. The skins perform like an I-joist’s flanges, and the rigid foam core is similar to the web. The individual elements work together to provide a strong, straight, and consistent structural unit with high load-bearing capacity.
As integrated structural and insulating units, SIPs replace wood or steel studs, joists, sheathing, and blown-in, batt, or sprayed-in-place insulation.
Walls
Because SIPs arrive at the jobsite in large sections (up to 8 feet by 24 feet), they make it easy to build smooth, even walls over long distances. SIPs eliminate the warping and bowing that can occur with stick-built construction.
Smooth walls look crisper and allow for faster, easier, and higher quality installation of doors, windows, cabinets, millwork, and other finishes. SIPs also provide a solid sheathed surface across each wall’s entire face, so they are not susceptible to having holes knocked in them like drywall over studs.
In earthquake and high wind areas, SIPs perform well, and can be used as shear walls to help buildings stand strong. They have been proven for use in the most stringent seismic zones, including design categories D, E, and F.
Roofs
SIPs provide strong, stable roofs, including long clear spans. A key benefit for streamlining construction is their ability to be used without an engineered truss system. Contractors frequently use SIPs in roof applications where large, open interior spaces are needed, such as school gymnasiums, cafeterias, manufacturing facilities, agricultural buildings, and similar uses. SIPs also provide an easy way to build cantilevered roofs with extended eaves or gable-end overhangs.
Floors
Contractors can also use SIPs for floors, although such applications are not as common as walls and roofs. They are typically used where an insulated floor system is required, such as over unheated spaces.
CONSTRUCTION TIME AND COSTS
SIP construction can help reduce the time needed to dry-in buildings since contractors can install entire wall, roof, and floor sections at one time. “Compared to stick framing, SIP walls go up much faster since they can be installed in large sections and eliminate the need for separate on-site framing and insulation work,” says Sharon Bullock, project manager with Community Development Programs Center of Nevada. “The finished walls are also beautifully straight, which saves time on drywall installation, painting, and other finishing work.”
SIPs can also decrease costs for HVAC systems, since their insulating properties and the reduced air leakage through the exterior building envelope allow for use of smaller-capacity equipment.
INSTALLATION CONSIDERATIONS
Manufacturers produce SIPs in a controlled environment and deliver them ready-to-install at the jobsite. This may include pre-cutting window and door openings, as well as chases for wiring.
Following are several key tips to keep in mind when building with SIPs. As with any building method, consult local codes for specific requirements, and follow the SIP manufacturer’s detailed instructions.
Storage and Handling
To facilitate construction, sort and stack panels as close to their final installed location as possible. SIPs typically come labeled corresponding to where they are to be placed according to the shop drawings. Store the panels flat and protect them from the elements.
Panel Connections
Depending on the load requirements and application, individual SIPs are typically joined with a block spline, a lumber spline, or wood I-joist. Mastic supplied by the manufacturer should be used on all wood-to-wood, wood-to-foam, and foam-to-foam interfaces. Once the panels are in place, the splines are nailed according to the nailing pattern shown on shop drawings.
Assembly
Whenever possible, use a scissor-like motion to place wall panels. This involves pushing the bottom corner so the skins touch and bracing it with your foot, then pushing the top into place. To help bring panels together, use either trucking straps or bar clamps. Panel pullers such as Jimmy’s Strapjack can also be used.
For exterior SIP walls, a water-resistive barrier, along with adequate weather protection, including flashing, is typically required. As with other wall assemblies, the design and materials should prevent moisture accumulation within the wall, and allow for drainage of water that penetrates the exterior wall covering.
Other Factors
The SIP manufacturer will typically provide detailed installation instructions and may offer training and field support. They usually will give guidance on correct fasteners, making field fabrications to panels, attaching SIPs to foundations and other structural elements, incorporating electrical and plumbing systems, and other common installation issues.
Many contractors who have made the switch to SIPs find them easier to work with than other building methods. The process is not complex, and extensive support is available.
