The International Code Council (ICC) updates their model building codes on a 3-year cycle. The latest version of their International Energy Conservation Code (IECC) is the 2021 IECC and contains multiple updates, or code changes, to the 2018 IECC as a result of a public process administered by the ICC. The code changes from the 2018 to the 2021 IECC result in both increased energy savings and construction costs, and this analysis quantifies the resulting cost-effectiveness.

Following U.S. Department of Energy cost effectiveness certification of the 2021 IECC, the National Association of Homebuilders (NAHB) commissioned the Home Innovation Research Labs (HIRL) to conduct an independent cost analysis of the 2021 IECC. The report, 2021 IECC Residential Cost Effectiveness Analysis (HIRL report), was published in June 2021, and asserted that the 2021 IECC imposed builder compliance costs of nearly $12,000 and homeowner payback periods of up to 79 years, depending on climate zone. This analysis is intended to “check the math” of the NAHB report using current cost data and widely accepted cost effectiveness metrics. To enable an easy comparison this report mirrors the HIRL Report structure, section by section and table by table, and is accompanied by a short comparison document titled Comparison of 2021 IECC Residential Cost Effectiveness Analyses, which also identifies concerns and issues identified in the HIRL report that were addressed.

This report was originally published in January 2022. In June of 2022 an updated version was published to revise cost calculations. Specifically, the method to apply the builders’ gross profit margin was updated as it was previously applied as a simple markup; and labor costs were increased to account for subcontractor overhead which was previously not included. Together these both increased the incremental cost of construction of the 2021 IECC; however, this did not change the overall conclusions of this analysis.

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