Massachusetts Specialized Energy Code Requirements for New Homes
New homes in the 60 Massachusetts communities that have adopted the Specialized (Opt-In) Code must follow one of three paths in 225 CMR 22 Appendix RC: Zero Energy (HERS 0 or Phius ZERO), All-Electric (HERS 45), or Mixed-Fuel (HERS 42 plus at least 4 kW of on-site solar per home and electric-ready wiring). Homes over 4,000 sq ft must be all-electric or zero energy, and residential buildings over 12,000 sq ft must meet Passive House.
Three paths
Zero Energy (HERS 0), All-Electric (HERS 45), or Mixed-Fuel (HERS 42 + solar + electric-ready). Over 4,000 sq ft: all-electric or zero energy only.
The Three Pathways (Appendix RC)
| Pathway | Requirement | Section |
|---|---|---|
| Zero Energy | Certified HERS rating of 0 or less, or Phius ZERO | RC102 |
| All-Electric | HERS 45 maximum (48 with embodied carbon credit), or Passive House (PHI or Phius CORE) | RC103 |
| Mixed-Fuel | HERS 42 maximum (45 with credit), on-site solar of at least 4 kW per dwelling (unless the potential solar zone is under 300 sq ft), and electric-ready circuits | RC104 |
Mixed-Fuel Electric-Ready Wiring (RC104.3)
- Gas or oil heating: a dedicated branch circuit labeled "For Future Heat Pump Space Heater".
- Gas range: a 250-volt, 40-amp outlet within 3 ft.
- Gas dryer or water heater: a 250-volt, 30-amp outlet within 3 ft, plus space for a future heat pump water heater.
- Future electric loads must be included in the service load calculation.
Size Limits and Passive House
- New homes over 4,000 sq ft of conditioned floor area must use the Zero Energy or All-Electric pathway (RC101.2).
- Residential (R-use) buildings over 12,000 sq ft must meet Passive House under R405, in addition to a pathway.
- All new buildings in Specialized towns must meet the Appendix RB solar-ready provisions (RC103.1).
We are a Phius Certified Rater and Verifier, so the same team handles the HERS rating and Phius verification.
Base vs. Stretch vs. Specialized
| Code | What it is | How many communities |
|---|---|---|
| Base | IECC 2021 with Massachusetts amendments (780 CMR Chapter 11R) | The rest of the state |
| Stretch | 225 CMR 22: HERS-based performance targets | 242 (required to be a Green Community) |
| Specialized | 225 CMR 22 plus Appendix RC: net-zero-ready new construction | 60 (required to be a Climate Leader Community) |
Additions and renovations in Specialized towns follow the Stretch Code's Chapter 5 rules. Some Specialized towns are also in the state's Fossil Fuel Free demonstration program and don't allow the Mixed-Fuel path at all.
FAQ
What is the Specialized Energy Code in Massachusetts?
An opt-in code (225 CMR 22 plus Appendix RC) that requires new homes to be net-zero ready through a Zero Energy, All-Electric or Mixed-Fuel pathway. 60 municipalities had adopted it as of June 4, 2026.
Can I build a gas house in a Specialized Code town?
Usually yes on the Mixed-Fuel path: HERS 42, at least 4 kW of on-site solar per home (unless the solar zone is under 300 sq ft) and electric-ready wiring. Homes over 4,000 sq ft can't use it, and towns in the Fossil Fuel Free program bar it.
What HERS score does an all-electric home need under the Specialized Code?
HERS 45 or lower (48 with the embodied carbon credit), or Passive House certification.
Do homes over 4,000 sq ft have special rules?
Yes. New homes over 4,000 sq ft of conditioned floor area must be all-electric or zero energy (RC101.2).
When is Passive House required in Massachusetts?
In Specialized Code towns, residential buildings over 12,000 sq ft must meet Passive House (R405).
Town-by-Town Permit Checklists
Local building department details, checked on each town's own website:
Sources: 225 CMR 22 with Appendix RC · Massachusetts building energy codes · Energy code adoption by municipality. Code text current as of October 2026; DOER has proposed updates to the Stretch and Specialized codes, so confirm before you file.
Related: Stretch code report for permitting · What triggers a HERS rating · REScheck and COMcheck · Phius verification
Building in a Specialized Code Town?
Send your plans today. Most projected HERS reports are ready in about one business day after the quote is accepted.
Mass Save®-Listed HERS Rater
U.S. DOE Efficient New HomeTrusted Partner — Verified
ENERGY STAR®Partner
Phius CertifiedPassive House Verifier
ICCMember★★★★★136 Google
Reviews
The Phius Certified Verifier logo is used under license from Phius.
