In opt-in Massachusetts towns, multifamily over 12,000 square feet must meet Passive House
In opt-in Massachusetts towns, multifamily over 12,000 square feet must meet Passive House
2026-09-10 · Massachusetts · Regulation
What happened. Massachusetts has an energy code that varies by municipality, and in the towns that have opted into its strictest tier, a multifamily building over a certain size must meet Passive House standards.
225 CMR 23.00 — the Stretch Code and municipal opt-in Specialized Code for commercial, multi-family and all other construction — carries 2025 amendments to IECC 2021 and ASHRAE 90.1-2019 that took effect 14 February 2025. The parallel low-rise residential chapter is 225 CMR 22.00. The Specialized Code's authority is M.G.L. c. 25A §6.1
The three-tier structure
- The base energy code, applying statewide
- The Stretch Code, a performance-based overlay appendix, adopted by most Massachusetts municipalities
- The Specialized Code, a municipal opt-in overlay designed for consistency with net zero by 2050, “primarily through a combination of energy efficiency… and efficient electrification”
The threshold
Under the Specialized Code in 225 CMR 23.00, multifamily buildings exceeding 12,000 square feet must meet Passive House compliance.
Twelve thousand square feet is not a large building. A modest Massachusetts condominium of a dozen units clears it comfortably.
Why an existing association can land inside it
The Specialized Code applies to new construction and, through the base code's existing-building chapters, to substantial alteration. A condominium association undertaking a gut renovation in an opted-in municipality can find itself inside a code tier it did not know existed.
Which code applies depends entirely on whether the city or town has opted in. The precise treatment of existing condominium buildings under the 2025 amendments — thresholds for alterations, and any exemptions — could not be confirmed and is unverified.
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Related Massachusetts HOA Topics
- 225 CMR 23.00, Massachusetts Stretch Code and Specialized Code for commercial, multi-family and all other construction, 2025 amendments ↩
- Massachusetts energy code: understanding the Stretch Code and the Specialized Code ↩
- Simpson Gumpertz & Heger, what changed in the Tenth Edition Massachusetts State Building Code ↩
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