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Using FPIS ci provides one of the most effective means insulating buildings to comply with the energy code because it insulates the entire structure to minimize thermal bridging of CFS framing materials. Without FPIS ci, the cavity insulation alone will deliver about 50% (or less) of its rated R-value. Consequently,   FPIS ci is generally required  for energy code compliance of buildings using CFS wall construction, regardless of the compliance path used (i.e., prescriptive path or performance path using total building simulation).FPIS ci also provides one of the more robust means of satisfying the moisture control requirements of the building code (refer to STEP 3).

The amount of FPIS ci can be adjusted as needed to target minimum code or other design objectives using this calculator tool.

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Alternatively, use the prescriptive wood-frame wall R-value recommendations below based on the 2024 edition of the International Energy Conservation Code (IECC) and your climate zone as shown in the map below. 

The FPIS ci material R-value specified and the FPIS material type selected (e.g., XPS, EPS, or PIC) will affect the thickness of the continuous insulation layer on the exterior of the wall. This thickness may affect other construction details, such as cladding connections (see STEP 4 later). In general, FPIS ci materials offer the advantage of thinner profiles to achieve required R-values in comparison to other continuous insulation material choices.  

NOTE: To address energy code whole building air leakage and air barrier requirements, refer to STEP 3 for coordination with water, vapor, and air control strategies.

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Overview

1. Determine your Climate Zone (see Figure 1 or Chapter 3 of the IECC [CE])
2. For the R-value recommendations, refer to Table 1 (A) or (B) below, the locally adopted energy code, the IECC, or ASHRAE 90.1 as appropriate.
3. For the prescriptive U-factor method to determine alternative R-value solutions for compliance, refer to the Steel Frame Wall Calculator.
4. For the Performance or Energy Rating Index compliance methods, refer to an energy modeling or energy rating professional to determine compliance.