The Northwest Energy Efficiency Alliance (NEEA) contracted with TRC to conduct a residential code evaluation in Washington, examining new construction single family homes built under Washington State Energy Code (WSEC) 2018. The evaluation estimated compliance with the code, primary space and water heating fuel selection, the proportion of homes with gas hook ups and gas-using appliances, builders’ selection of energy credits, and other characteristics including envelope, heating and cooling, ventilation, and water heating choices.
From September 2022 to January 2023, TRC conducted virtual home audits with a representative sample of 56 new homes and collected permit data for those homes. Findings indicate that 76% of homes built under WSEC 2018 have the required number of energy credits for a home of its size. The study also found a shift towards electric space heating and water heating, although the majority of homes built under WSEC 2018 had a gas hookup.
This report was updated on 7/20/23 to correct an error on page 32. The corrected statement now reads “Of the 44 audited homes with electric primary space heating, four (or 9%) were found to have a gas furnace as a backup or secondary system…”