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MBPE clears residential energy‑code proposals for council; ERI path, home‑size credits and PV/storage drew heated debate
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Summary
The MBPE committee voted July 18 to transmit the residential tag’s proposals to the Building Code Council for rule‑making (CR‑102). Key additions include an ERI pathway, revised home‑size credit banding, updated fenestration UA targets and a contested discussion over rooftop solar and battery‑storage credits.
The MBPE committee voted on July 18 to forward the residential energy‑code proposals to the Building Code Council, approving a package that includes a new Energy Rating Index (ERI) pathway, revised home‑size credit bands, an updated baseline fenestration U‑value and several related clarifications.
What the package would do: The tag added a new ERI pathway (an energy‑rating, HERS‑style approach) as an alternate compliance path to the existing prescriptive and modeling routes. The tag also revised how home sizes map to credit requirements: it smoothed the jump between size bands to avoid a large credit increase when a home crosses a single square‑foot threshold and created contingency credit levels depending on whether the council also adopts two tied edits (a 0.27 fenestration U‑value and a 3 ACH air‑leakage limit).
Modeling and scope: Unlike the commercial C406 modeling contract, the tag did not commission third‑party modeling to update the R406 credits; PNNL and NIA were working on modeling for the modeling pathway (R405) and ERI, but not the R406 credit table. Tag members stressed the need for modeling to verify progress toward the council’s glide path.
PV and energy storage: The committee spent considerable time on whether and how to allow on‑site PV and battery storage to count toward the residential options table credits. Two competing amendments were discussed. One, supported by solar‑industry commenters and some tag members, proposed modestly increasing the maximum solar/storage credit availability if paired with on‑site battery storage (to encourage grid‑friendly, on‑site use). Opponents warned that increasing rooftop PV credit potential risks letting projects meet compliance primarily with rooftop PV instead of long‑lived envelope and equipment measures. The committee ultimately approved a compromise that allows some storage‑paired credit but preserves limits on how much onsite renewables can count toward the ERI/prescriptive credit totals; the committee also asked that the modeling and public comment process address carbon and grid‑use implications.
Other notable items and debates: - Electric readiness and spaces for future heat‑pump circuits: The committee approved a modification that requires space in the service panel (a two‑pole breaker space) sized in a manner consistent with the electrical code and heat‑pump sizing guidance; members rejected a broader requirement to install a complete dedicated branch circuit and outlet at construction time, citing cost and siting uncertainty. - Replacing AC with heat pumps in existing buildings: The tag proposed that, when replacing AC-only equipment, owners either install heat pumps or meet other performance options (duct sealing, etc.). Some members raised EPCA (federal law) concerns about mandating changes on replacement; the committee forwarded the tag language with a record that this was a debated item and pointed to public comment as the venue for further legal and policy review. - Integrated‑draft edit for UA baseline: The committee adopted an edit restoring a 15% baseline glazing area used in the UA trade‑off baseline (the integrated draft had adopted a new equation that unintentionally removed that baseline). Supporters called the change necessary to avoid a code rollback that would encourage excessive glazing.
Vote and next steps: The MBPE committee voted to forward the residential package to the council for CR‑102 filing with the set of amendments and clarifications the committee approved during the meeting. Council staff indicated the CR‑102 and the PNNL/NIA modeling results (where available) should be posted for public comment so stakeholders can review interactive modeling results and submit comments before the council’s hearings.
Public comment highlights: Solar installers and storage providers urged credit recognition for batteries to support grid reliability and avoid investments in transmission or peaker plants; builders and some tag members cautioned that credits must still prioritize long‑lived envelope upgrades. Builders noted real‑world retrofit constraints (attic geometry, hydronic heating, ice‑dam risk) when forced to relocate equipment in existing homes.
