Idaho, Montana, and Oregon Residential Energy Code Savings Analysis

The Northwest Energy Efficiency Alliance (NEEA) contracted with Ecotope to conduct an analysis of Idaho, Montana, and Oregon energy codes. The study sought to quantify the energy use, energy savings and incremental costs for residential code improvements previously adopted in these states using evaluation procedures aligned with previous protocols for estimating code stringency. Ecotope compared the previous energy code with the current residential energy code for single-family (including townhomes) and low-rise multifamily units of three stories or less constructed under the residential code in each state. This provides a comparison between the codes in each state. The resulting calculated savings for each state is an analysis of the energy codes as published and does not account for industry trends and product adoption in the market. The energy codes analyzed include the 2018 International Energy Conservation Code (IECC) with Idaho amendments, the 2018 IECC with Montana amendments, and the 2021 Oregon Residential Specialty Code (ORSC).

Findings from the analysis show that adoption of the 2018 IECC with amendments in Idaho realized a substantial advancement in energy efficiency of homes with 11.6% savings increase over the previous residential energy code. Montana’s adoption of the 2018 IECC with amendments resulted in 2.5% savings over the previous code. In Oregon, adoption of the 2021 ORSC resulted in -2% savings compared to the previously adopted code.

An updated addendum is included at the end of this report which provides a revised analysis of the 2021 ORSC after stakeholders identified a few potential errors and inconsistencies in the modeling inputs and assumptions used in the original Oregon analysis.

(Note: this report analyzes a previous version of each state’s residential energy code; more recent energy codes have been adopted in each state since this report was published. Idaho updated its 2018 IECC as part of the Zero-Based Regulation process, Montana adopted the 2021 IECC with amendments, and Oregon adopted its 2023 ORSC. This report does not address these latest code versions.)

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