Structural Insulated Panels (SIPs) Seams
No climate specific information applies.
SIPs consist of two layers of plywood or OSB that “sandwich” an inner core of insulating rigid foam. Panels are spliced together using splines, consisting of strips of OSB, SIPs, or 2x4 or 2x6 lumber. The seams where one panel joins another are susceptible to air leakage. To form an air tight bond, spray foam or caulk is applied to the seams before the panels are connected. Many SIP manufacturers will provide the caulk and instructions. The wall-floor, wall-wall, and wall-roof seams can each require as many as six beads of caulk, and the roof ridge seam can require up to 8 beads of caulk.
After caulking, the panels are fit together to assemble the structure. To ensure that joints lock tightly together, a belt winch can be used to pull wall assemblies together; this is especially helpful with larger panels. Before drywalling, the seams can be covered with peel and stick tape as a second layer of protection against air leakage. Before installing drywall is also an ideal time to test the air tightness of the seams with a blower door test and smoke pencil to visually identify the location of any leaks.
Air barrier effectiveness is measured at the whole-house level. High-performance branding programs and the 2009 International Energy Conservation Code (IECC) require that builders meet specified infiltration rates at the whole-house level. See the “compliance” tab for these specified infiltration rates.
For more information on SIP installation, see Structural Insulated Panels.
How to Seal SIP Seams
1. Connect the panels with splines. The three most common splines are surface splines, insulated splines, and structural spines (see Figures 1, 2, and 3). To minimize thermal bridging, only use structural splines when needed to carry the structural load. Splines can be installed on one side of the panel in the factory; this can save assembly time at the site.
2. Caulk on each side of the spline. Use caulk from the manufacturer, if provided. Follow the caulking schedule required by the SIP manufacturer for the number of beads of caulk to use at each type of seam. Make sure the beads are continuous. Consider using a power caulker; even in a small (1,200 sq. ft.) home, the amount of caulk required can total over 5,000 lineal feet of caulk.
3. Assemble the walls and roof. Use a fork lift and crane to place panels. Use lift plates and a belt winch (available from the manufacturer) to pull panels together tightly, if needed (Figure 4).
4. Install peel-and-stick tape at panel-to-panel seams and at the ridge and wall-roof interface (See Figure 5).
5. Prior to drywalling, conduct a blower door test and use a smoke pencil to ensure that panel seams are tight (Figure 6).
The air tightness of the envelope assembly of a home constructed with structural insulated panels can be easily tested by conducting a whole-house blower test prior to dry wall installation. While the house is depressurized, inspect all panel seams with a smoke stick. An infrared camera may also be helpful in spotting air leakage, if a sufficient temperature difference exists between the outside and the inside of the home.
All seams between Structural Insulated Panels (SIPs) foamed and/or taped per manufacturer’s instructions.
- Apply manufacturer-approved sealant inside the joints of all panels and at sub-floor or foundation connections.
- When applying tape to walls, center on joints and provide overlap of tape to meet manufacturer’s specifications.
- When applying tape to roof panels, start from the lowest point of the panel and continue upward.
Thermal Enclosure Checklist, Air Sealing. Cracks in the building envelope fully sealed. All seams between Structural insulated Panels (SIPs) foamed and/or taped per manufacturer’s instructions
DOE Challenge Home
Exhibit 1: Mandatory Requirements. Certified under ENERGY STAR Qualified Homes Version 3
The 2009 IECC does not specifically address sealing SIP seams. Table 402.4.2 Air Barrier and Insulation Inspection Component Criteria, Walls: Corners, headers, narrow framing cavities, and rim joists are insulated.*
The 2009 IRC has several diagrams in Section R613 Structural Insulated Panel Wall Construction that illustrate the placement of continuous sealant.
The 2012 IECC does not specifically address sealing SIP seams. Table R402.4.1.1 Air Barrier and Insulation Installation, Walls: Junction of foundation and wall sill plates, wall top plate and top of wall, sill plate and rim-band, and rim band and subfloor are sealed. Corners, headers, and rim joists making up the thermal envelope are insulated.*
The 2012 IRC has several diagrams in Section R613 Structural Insulated Panel Wall Construction that illustrate continuous sealant. Table N11402.4.1.1 Air Barrier and Insulation Installation, Walls: Junction of foundation and wall sill plates, wall top plate and top of wall, sill plate and rim-band, and rim band and subfloor are sealed. Corners, headers, and rim joists making up the thermal envelope are insulated.*
*Due to copyright restrictions, exact code text is not provided. For specific code text, refer to the applicable code.