Washington State Adopts New Residential Energy Code With ERI Pathway

The Building Code Council convened on July 25, 2025, to discuss significant updates to the residential energy code, which are set to be released for public comment. The meeting, led by Kjell, chair of the residential energy code technical advisory group (TAG), focused on the completion of a draft that underwent extensive review over seven meetings totaling approximately 40 hours.

Key changes to the residential energy code include the introduction of the Energy Rating Index (ERI) pathway, which has not been previously adopted in Washington. This new energy modeling pathway aims to provide builders with additional options for compliance alongside existing prescriptive paths. The TAG approved this addition without contention, although concerns were raised about the potential confusion it may cause for code officials managing multiple modeling pathways.

The council also approved modifications to the energy credit requirements for homes based on size, creating a smoother transition in credit requirements as home sizes increase. For instance, homes between 1,525 and 1,750 square feet will now have a more gradual increase in energy credits required.

Further updates included adjustments to the U-value for fenestration, which was lowered from 0.28 to 0.27, aligning it with the R-value of walls. This change reflects the TAG's belief that the market is ready for improved energy efficiency standards. Additionally, the council reinstated a previous air tightness testing requirement of 3 air changes per hour (ACH), which had been weakened in the last code cycle.

A notable requirement for energy recovery ventilation systems was also approved for Zone 5B in Eastern Washington, emphasizing the need for efficient heating and cooling solutions in the region. The council discussed the removal of solar-ready requirements from electrical inspections, deeming it more appropriate for other codes.

The meeting concluded with the approval of several minor modifications and clarifications to the code, including updates to the definitions and requirements for heat pumps. These changes reflect the council's ongoing commitment to enhancing energy efficiency and sustainability in residential construction across Washington State. The next steps involve public comment on the proposed changes, allowing for community input before final adoption.