TAG approves combined ERI pathway proposal; asks modelers to refine renewables cap and envelope backstop

The Washington State Residential Energy Code TAG voted June 27, 2024, to approve a combined ERI compliance proposal that adapts 2024 IECC language to Washington State code and establishes local rules for on‑site renewables and envelope tradeoffs. The approval was unanimous after extensive discussion about renewable caps, how on‑site renewable energy certificates (RECs) can be used, and quality assurance for ERI raters. Why it matters: The ERI path is a performance option that allows builders to meet code using modeled whole‑house energy performance rather than prescriptive measures. A clear ERI path that aligns with national standards but reflects state policy allows larger builders and national programs to operate in Washington while retaining local policy controls. Key outcomes and technical choices: - TAG approved the combined O33/O40 package (the TAG referenced the combined file as 040/033) and directed staff to include the changes in public materials. The group's vote to approve the combined ERI proposal was unanimous. - Renewable energy: TAG asked the ERI language to adopt an upper limit on how much on‑site renewables (measured in kWh/year) may count toward ERI compliance so the ERI path does not allow buildings to meet code by substituting large solar arrays for efficiency. The work group proposed a cap aligned with the prescriptive path's renewable credit limit (around 5,400–6,000 kWh equivalency), and TAG asked for that cap to be updated to match a small increase that was adopted elsewhere in the prescriptive table. - Envelope backstop: The IECC ERI path allows limited weakening of the thermal envelope if other measures compensate. TAG discussed whether Washington should allow a 10 percent weakening (as proposed by some work group members) or a larger 15 percent weakening (the 2024 IECC value). After debate, TAG voted down an amendment to increase the allowed weakening; the TAG kept the more conservative 10 percent (1.10) backstop in the approved proposal. Members said they want PNNL analysis on how envelope tradeoffs affect net energy and compliance. - RECs and on‑site renewables: TAG members asked the draft to make clear that RECs must be tied to on‑site generation to count toward ERI ("RECs must be generated by on‑site renewable generation to count"), avoiding counting unbundled off‑site RECs as compliance energy. - Third‑party quality assurance: TAG discussed whether raters must register with a program (ResNet or similar) and whether building officials may require proof of QA. TAG added language requiring raters/third‑party rating providers to be subject to quality assurance; TAG asked staff to refine that language with Jonathan and to return clarified wording at the next committee meeting. What members said: - Kevin Rose (Northwest Energy Efficiency Alliance) and Rob Salcedo (PNNL) briefed the TAG on the ERI options. Kevin emphasized alignment with the national model and that the major outstanding issues were ERI target values, renewable caps, and the envelope backstop. - Rob Salcedo (PNNL) told the TAG PNNL can run the modeling required to generate ERI target tables for the different dwelling size buckets and climate zones during the public comment/modeling window if the TAG requests it. Voting and next steps: - TAG approved the combined ERI proposal in a recorded action; the group asked PNNL to model ERI targets for the two climate subzones (4C and 5B) and to test how the renewable‑energy cap and the envelope backstop influence final ERI values. - TAG asked staff to post the combined ERI language for the MVPE committee meeting and public comment, and to capture the modeling assumptions and thresholds for auditability. Ending note: TAG members emphasized the need to return to the Council with transparent analysis showing how the ERI path compares, in site energy terms, to the prescriptive path and to document any differences in how renewables are treated.