Air Sealing Structural Insulated Panel (SIP) Seams

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All seams between structural insulated panels (SIPs) foamed and/or taped per manufacturer's instructions
All seams between structural insulated panels (SIPs) foamed and/or taped per manufacturer's instructions
Scope

Air Sealing

Seal all seams between Structural Insulated Panels (SIPs) with foam and/or tape per manufacturer’s instructions.

  • Apply manufacturer-approved sealant inside the joints of all panels and at the sub-floor or foundation connections.
  • When applying tape to walls, center it on the 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.

See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and Indoor airPLUS.

Description

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.
    A surface spline reduces thermal bridging much more than a structural spline at SIP panel seams

    Figure 1 - A surface spline reduces thermal bridging much more than a structural spline at SIP panel seams.

    An insulated spline is another option for avoiding thermal bridging at SIP panel seams

    Figure 2 - An insulated spline is another option for avoiding thermal bridging at SIP panel seams.

    A structural spline made of a solid 2x is used where needed to meet structural load requirements at SIP panel seams

    Figure 3 - A structural spline made of a solid 2x is used where needed to meet structural load requirements at SIP panel seams.

  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).
    Lifting plates attached to the wall provide good bracing to tighten up SIP panel seams

    Figure 4 - Lifting plates attached to the wall provide good bracing to tighten up SIP panel seams.

  4. Install peel-and-stick tape at panel-to-panel seams and at the ridge and wall-roof interface (See Figure 5).
    Peel-and-stick panel tape provides added assurance that SIP panel seams will remain airtight

    Figure 5 - Peel-and-stick panel tape provides added assurance that SIP panel seams will remain airtight.

  5. Prior to drywalling, conduct a blower door test and use a smoke pencil to ensure that panel seams are tight (Figure 6).
    Use a smoke pencil to check for air leaks at SIP panel seams, especially along the ridge beam
    Figure 6 - Use a smoke pencil to check for air leaks at SIP panel seams, especially along the ridge beam.
Ensuring Success

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. 

Climate

No climate-specific information applies.

CAD

Compliance

The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

ENERGY STAR Certified Homes, Version 3/3.1 (Rev. 09)

National Rater Field Checklist

Thermal Enclosure System.
2. Fully-Aligned Air Barriers 6 At each insulated location below, a complete air barrier is provided that is fully aligned as follows:
Walls: At exterior vertical surface of wall insulation in all climate zones; also at interior vertical surface of wall insulation in Climate Zones 4-8.8

4. Air Sealing (Unless otherwise noted below, “sealed” indicates the use of caulk, foam, or equivalent material). 
4.1 through 4.10 describe air sealing details for specific components of the building envelope.

Please see the ENERGY STAR Certified Homes Implementation Timeline for the program version and revision currently applicable in in your state.

DOE Zero Energy Ready Home (Revision 07)

Exhibit 1 Mandatory Requirements.
Exhibit 1, Item 1) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.

2009 International Energy Conservation Code (IECC)

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.

2012, 2015, and 2018 IECC

The 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.

Retrofit: 

2009, 2012, 2015, 2018, and 2021 IECC

Section R101.4.3 (Section R501.1.1 in 2015, 2018, and 2021 IECC). Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with this code. (See code for additional requirements and exceptions.)

2009 International Residential Code (IRC)

The 2009 IRC has several diagrams in Section R613 Structural Insulated Panel Wall Construction that illustrate the placement of continuous sealant. 

2012, 2015, and 2018 IRC

The IRC has several diagrams in Section R610 (Section R613 in 2012 IRC) Structural Insulated Panel Wall Construction that illustrate continuous sealant. Table N1102.4.1.1 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.

Retrofit: 

2009, 2012, 20152018, and 2021 IRC

Section N1101.3 (Section N1107.1.1 in 2015 and 2018, N1109.1 in 2021 IRC). Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with this code. (See code for additional requirements and exceptions.)

Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their continued safe use.

More Info.

Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

References and Resources*
Author(s)
U.S. Environmental Protection Agency
Organization(s)
EPA
Publication Date
Description
Guide describing details that serve as a visual reference for each of the line items in the Thermal Enclosure System Rater Checklist.
Author(s)
Miller,
Kosny,
Shrestha,
Christian,
Karagozis,
Kohler,
Dinse
Organization(s)
Oak Ridge National Laboratory,
Lawrence Berkeley National Laboratory
Publication Date
Description
Report about four homes in the Tennessee Valley built to showcase 50% greater energy efficiency compared to homes built to local code.
Author(s)
Christian
Organization(s)
Oak Ridge National Laboratory
Publication Date
Description
Report presenting construction methods, building products, appliances and equipment of four single-family houses that achieve dramatic energy reductions and approach “net zero energy” use.
Author(s)
U.S. Environmental Protection Agency
Organization(s)
EPA
Publication Date
Description
Website providing the technical specifications and related documents for home builders, subcontractors, architects, and other housing professionals interested in certifying a home to the EPA's Indoor airPLUS program requirements.
*For non-dated media, such as websites, the date listed is the date accessed.
Building Science Measures
Building Science-to-Sales Translator

Structural Insulated Panels (SIPs) = SIP Thermal Blanket

Image(s)
Technical Description

Structural insulated panels (SIPs) are a sandwich made up of foam insulation glued between two layers of sheathing (e.g., oriented strand board, magnesium oxide board, or drywall). SIP wall and roof panels are produced in a factory and come to the job site clean, dry, straight, and precisely made to the wall dimensions specified in the house plans with precut openings for doors and windows. They assemble quickly, producing a sturdy, well-sealed, well-insulated structure. Because there is minimal to no framing, the foam core provides a nearly continuous thermal blanket around the entire structure so heat transfer through the framing is greatly reduced.

SIP Thermal Blanket
Sales Message

SIP thermal blanket construction blocks excessive heat loss and gain though structural framing. What this means to you is less wasted energy along with enhanced comfort and quiet. Knowing there is one opportunity during construction to lock in quality construction, wouldn’t you agree advanced thermal protection is a great investment?

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