Building Codes

Yes, if you’re following the prescriptive requirements. However, if you opt to earn points in R406.3 (options 1.1 – 1.4) and meet or surpass the reduction percentages for total UA, there’s potential to forgo using continuous insulation. To use this option and prove the reduction, you will need to use the C3 calculator published by WSU Energy. Since 2009, the C3 calculator has been a state endorsed compliance tool.

Below is hierarchical code language illustrating the two options for builders/designers: prescriptive OR the Total UA Alternative. Pursuing the Total UA Alternative helps you achieve credits toward the overall required credit thresholds.

• Efficient Building Envelope Options – Only one option from Items 1.1 through 1.4 may be selected in this category.
• Compliance with the conductive UA targets is demonstrated using Section R402.1.5, Total UA alternative, where [1-(Proposed UA/Target UA)] > the required %UA reduction.
• 1.5 Total UA alternative.If the proposed building thermal envelope UA is less than or equal to the target UA, the building shall be considered in compliance with Table R402.1.2. The proposed UA shall be calculated in accordance with Equation 2. The target UA shall be calculated in accordance with Equation 1. U-factors shall be determined as specified in Section R402.1.6. In addition to UA compliance, the maximum fenestration U-factors of Section R402.5 shall be met.
• ‍TABLE R402.1.2  Above-Grade Wall U-Factor – 0.056 Option 1.2
• Prescriptive compliance is based on Table R402.1.3 with the following modifications:
  Vertical fenestration U = 0.25
  Floor R-38
  Slab on grade R-10 perimeter and under entire slab
  Below grade slab R-10 perimeter and under entire slab
  or Compliance based on Section R402.1.5: Reduce the Total conductive UA by 15%. 

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‍Download the C3* Calculator and Permit Forms at this link
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‍Please note: C3 requires Excel for Windows installed on your computer (not web-based) and is not available for Mac computers. Disclaimer: Results from the C3 assume that all data is entered correctly and completely. Results do not constitute an official decision. Your analysis should be reviewed by your building official/authority having jurisdiction.

*C3 means code compliance calculator.

All information, content, and materials regarding pathways for energy code compliance are for general informational purposes only, and do not constitute a formal recommendation from the Building Industry Association of WA (BIAW). No reader or user of this information should act or refrain from acting on the basis of this information without consulting the appropriate professionals. All liability with respect to actions taken or not taken based on the information provided are hereby expressly disclaimed.

Medium Dwelling Unit = 8 credits needed
R406.2 Energy Equalization Credits

Ductless Mini-Split: Type 4 = 3 credits R406.3 Energy Credits

• ‍Option 1.2 = 1 credit
• Option 3.7 = 2 credits
• ‍Option 5.6 = 2 credits

BIAW has compiled the credit options, and required pairings of credits, for use by our members. To view, click the “See the Board” button below.