The Northwest Energy Efficiency Alliance (NEEA) contracted with TRC to gather market data about the impact of the 2018 Washington State Energy Code (WSEC) on new construction single family homes in Washington in the first year after the code was in effect. The study explored primary space and water heating fuel selection, builders’ selection of energy credits, and other characteristics including envelope, heating and cooling, ventilation, and water heating choices.
From December 2021 to March 2022, TRC conducted a review of a representative sample of 178 permits for new homes built to comply with WSEC-2018 along with surveys of 26 code compliant and above-code builders in the state. Findings from the permit data indicate that builder practices have changed under the 2018 WSEC compared to the 2015 WSEC. This includes a shift towards electric space heating and water heating and a preference for efficient equipment options over changes in construction techniques. No site visits were conducted as part of this study to verify installed conditions.