Foam Plastic Insulating Sheathing (FPIS)—often called foam sheathing or rigid foam board—has many benefits and can deliver up to five essential building enclosure functions in one product as shown in the figure below. 

(Note: All code references are to the 2024 editions unless otherwise noted.)

FPIS installed as continuous insulation extends without interruption across framing and other structural members to minimize the effect of thermal bridges and improve building thermal performance. FPIS ci satisfies energy code insulation requirements such as IECC Section C402.1.3 and IECC Section R402.1.3 for commercial and residential buildings, respectively. The Wood Frame Wall Calculator and Steel Frame Wall Calculator provide simple and flexible means to comply with the energy code while simultaneously addressing code-compliant water vapor control (see below).

FPIS ci provides a robust and code-compliant means of managing water vapor diffusion in all climates and all seasons when used with the right combination of vapor retarder for inward drying potential and minimum ci R-values to control temperatures inside an assembly. IBC Section 1404.3 and IRC Section 702.7—together with this 3-Step Quick Guide, the Wood Frame Wall Calculator, or the Steel Frame Wall Calculator—make it simple to find the right solution for your project.

With rigorous code-compliance testing, many FPIS products are recognized as part of a code-compliant WRB system when installed per manufacturer instructions (including specified joint tape and flashing components). While previously considered an approved alternative WRB method, the 2024 IBC/IRC explicitly recognize FPIS WRB systems that comply with IBC Section 1403.2 and IRC Section R703.2.

Most FPIS panels qualify as air barrier materials. Air-barrier system performance depends on sealed panel joints and transitions (same as FPIS ci WRB systems) as well as other routine air leakage sealing practices (e.g., sealing at penetrations and assembly transitions). Control of air leakage also compliments the control of water vapor. For energy code air barrier, air-sealing, and whole building testing requirements refer to IECC Section C402.6 and IECC Section R402.5.

Where coupled with a structural laminate or facer, FPIS ci can provide a code-compliant means for wall bracing for resistance to earthquake and wind lateral (racking) forces. Certain composite or proprietary systems combine structure + ci + WRB + AB + VR for “5-in-1” performance. Such integrated products using FPIS can result in optimized wall assemblies for structural, thermal, and moisture-resistant performance. Refer to the specific manufacturer’s code compliance data for appropriate use. In general, wall bracing to resist wind and seismic loads requires either an engineered design (common for commercial buildings) or application of prescriptive provisions for one- and two-family dwellings (e.g., IRC Section R602.10). Whether using a structural insulated sheathing version of FPIS ci or not, refer to the IRC Wall Bracing Code-Compliance Guide and the IRC Wall Bracing Calculator found here for assistance in integrating foam sheathing into a code compliant wall bracing design.

 

Why Multifunction Matters

Leveraging the multi-functional capabilities of FPIS ci can: 
è satisfy multiple code minimum requirements or above-code objectives with one product 
è result in robust assemblies that are simpler to construct 
è deliver optimized cost vs. performance 

LEARN MORE: Multifunctional Applications & Code Compliance for Foam Sheathing Continuous Insulation   

 

Where FPIS Works (Residential & Commercial Building Applications)

The multiple functions of FPIS can be put to work on a variety of code-compliant residential and commercial building applications including: 

  • Roofs
  • Floors
  • Walls
  • Windows
  • Foundations 

For more information about how the multi-functional capabilities of FPIS ci can be used to comply with Above-Code Performance Programs, check out these resources: