DOER’s Updated Stretch Code – A Breakdown of the Changes and the New Opt-in Net Zero “Specialized Code”

October 20, 2022

Key Takeaways:
  • The updated Stretch Code creates stricter guidelines for almost all new construction and alterations in municipalities that have opted-in to the Stretch Code
  • The Stretch Code has a phase-in period, with even stricter requirements for new home construction starting July 1, 2024
  • The newly created Specialized Code goes beyond the Stretch Code to impose requirements intended to ensure that new construction is consistent with the long-term goal of creating a net-zero economy by 2050
  • Municipalities must elect to opt-in to the Specialized Code separately from the Stretch Code

Massachusetts will soon see significant updates to the energy codes that govern the construction and alteration of buildings throughout the Commonwealth. As required by the 2021 climate bill, the Massachusetts Department of Energy Resources (DOER) has recently finalized a set of regulations that update the current Stretch Energy Code, previously promulgated by the state’s Board of Building Regulations and Standards (BBRS), and establish a new Specialized Code geared toward achieving net-zero building energy performance. The final code (summarized by DOER here) has been submitted to the Joint Committee on Telecommunications, Utilities, and Energy for review as required under state law.

Under the new regulations, each municipality must apply one of the following:
  • Base Energy Code – The current Base Energy Code is being updated by the BBRS as part of its routine updates to the full set of building codes. This base code is the default if a municipality has not opted-in to an alternative energy code.
  • Stretch Code – The updated Stretch Code creates stricter guidelines on energy efficiency for almost all new construction and alterations in municipalities that have adopted the previous Stretch Code. With roughly 90% of Massachusetts municipalities having adopted the Stretch Code, these new energy standards will have an impact on building requirements throughout the Commonwealth. The updated Stretch Code will automatically become the applicable code in any municipality that previously opted-in to the Stretch Code.
  • Specialized Code – The newly-created Specialized Code includes additional requirements above and beyond the Stretch Code, designed to ensure that new construction is consistent with a net-zero economy by 2050. Municipalities must opt-in to adopt the Specialized Code by vote of City Council or Town Meeting.
The Updated Stretch Code

The updated Stretch Code layers additional requirements on top of the Base Energy Code for two categories of buildings:  Residential Low Rise and Commercial/all other.

Residential Low-rise Construction (225 CMR 22)

The updated Stretch Code has kept the two existing compliance pathways, Home Energy Rating Scores (HERS) and Passive Compliance, but has amended them in the following ways:

Home Energy Rating Scores (HERS)
The maximum allowable HERS has been lowered for both new construction and alterations. For new construction, there will be a phase-in period under which an interim standard (identical to that in the updated Base Energy Code) will apply until July 1, 2024.
On-site Clean
Maximum HERS Index score (before renewable energy credit)
New construction Alterations, Additions
and Change of use
Current Stretch Code Updated
Stretch Code

Through 6/30/2024
Updated Stretch Code
Current Stretch
Stretch Code

None (Fossil fuels) 55
52 42
65 52
Solar 60 55 70 55
All-Electric 60
55 45
70 55
Solar & All- Electric 65 58 75 58

Passive House Certification
The Stretch Code has been updated to allow for the 2021 Passive House Institute US standard (updated from the 2018 standard), in addition to continuing to allow the Passive House International standard. 

The updated Stretch Code has also added several requirements for new residential construction:
  • Ventilation requirements through either heat recovery or energy recovery.
  • A minimum of 20% of parking spaces in a multi-family parking lot must be wired for EV charging. This is increased from 10% in the previous Stretch Code.
  • Clarifies that home additions over 1,000 square feet, additions that more than double the size of the house, and alterations to over 50% of the home, must follow the HERS pathway and meet the HERS requirements for Additions above. Additions under 1,000 square feet may follow the Base Energy Code. 
Commercial Construction (225 CMR 23)

The updated code provides multiple compliance pathways for four major categories of buildings:
  • Offices, residential, and schools over 20,000 square feet
    • Required to use the new Thermal Energy Demand Intensity (TEDI) pathway to compliance. TEDI is an energy software calculation that focuses on heating, cooling, and building envelope, the updated Stretch Code includes specific TEDI limits by building type.
  • High ventilation buildings
    • The code continues to recognize the particular energy needs of high ventilation buildings such as labs and hospitals. These buildings can continue to use the “10% better than ASHRAE App. G” pathway (which is being phased out for other uses) or use the TEDI pathway mentioned above. 
  • Small commercial buildings under 20,000 square feet (any use except multi-family)
    • May comply through an updated prescriptive pathway or can use the TEDI pathway. 
  • Large multi-family buildings
    • Can choose between HERS and Passive House compliance pathways the same way as low-rise residential buildings. 
Availability of some of these pathways will be phased out and updates will be phased in, depending upon building type. Mixed-use buildings can use a combination of code pathways for different portions of the building or can take a whole-building approach.

There are also several additional requirements for commercial buildings under the updated Stretch Code, including new requirements related to electrification of space heating, enhanced ventilation energy recovery requirements, an increase in the percentage of business use parking spaces that must be wired for electric vehicle charging to 20%, and a requirement that alterations and changes of use and occupancy in commercial buildings now follow the prescriptive pathway under the Stretch Code (with a 10% reduced envelope requirement), rather than the Base Code.

The Specialized Code
Starting on December 24, 2022, municipalities will be able to opt-in to adopt the Specialized Code, by vote of Town meeting or City Council. The Specialized Code was designed to be consistent with the Commonwealth’s 2050 net-zero construction goals. In general, it focuses on deep energy efficiency, reduced heating loads, and efficient electrification. It requires that all new buildings be designed with electric service and, where fossil fuels are to be utilized, wiring to enable electrification of space and water heating in the future.

Residential Low-rise Construction (225 CMR 22, Appendix RC)

The specialized code offers three pathways for residential homes:
  • Zero Energy Pathway
    • A building is zero-energy if there is a net-zero consumption of energy over the course of a year, excluding energy use for charging vehicles. 
      • A zero energy building may comply with either the HERS 0 Performance Standard or the Phius ZERO Performance Standard. Under the Specialized Code, contracts for Renewable Energy Credits or off-site Renewable Energy Sources cannot be counted towards Phius ZERO certification.
  • All-Electric Pathway
    • Residential homes may qualify if they do not utilize fossil fuels and comply with either HERS 45 or the Passive House Pathway in the updated Stretch Code.
  • Mixed-Fuel Pathway
    • New low-rise buildings must meet minimum efficiency requirements of HERS 42 or the Passive House Pathway.
    • Must be fully wired for future conversion to all-electric. 
    • If utilizing the HERS Pathway, must install solar panels to mitigate near-term emissions.
    • If larger than 4,000 square feet, new buildings must meet HERS 0 or Phius ZERO requirements.
New homes up to 4,000 square feet may follow any of the three, whereas new homes over 4,000 square feet must follow either the zero energy or the all-electric pathways and may not utilize fossil fuels.

Notably, buildings that utilize fossil fuels may still meet the requirements as a net-zero building if they are fully wired for future electrification and generate solar power on-site.
Building Size Fuel Type Minimum Efficiency Electrification Min. EV wiring Renewable Generation
Dwelling units up to 4,000 sf All
HERS 45 or Phius CORE or PHI Full 1 parking space Optional
Dwelling units up to 4,000 sf Mixed-
HERS 42 or Phius CORE or PHI Pre-wiring 1 parking space Solar PV (except shaded sites)
Dwelling units > 4,000 sf All
HERS 45 or Phius CORE or PHI Full 1 parking space Optional
Dwelling units > 4,000 sf Mixed-
HERS 0 or Phius ZERO Pre-wiring 1 parking space Solar PV or

Multi-family >12,000 sf All
Phius CORE or PHI Full 20% of spaces Optional
Multi-family >12,000 sf Mixed-
Phius CORE or PHI Pre-wiring 20% of spaces Optional

Commercial Construction Specialized Code (225 CMR 23, Appendix CC)

All commercial construction under the Specialized Code must meet the same minimum energy efficiency requirements as under the updated Stretch Code. In addition, under the Specialized Code, construction must meet the performance standards set out in one of the three following pathways: 
  • Zero-Energy Pathway
    • Annual zero energy must be demonstrated only by on-site generation, typically through solar panels, which must exceed annual building energy use. Must also meet minimum energy efficiency requirements prior to renewable offsets.
    • Multi-family residential buildings may also use either HERS 0 or Phius ZERO certification, as in the low-rise residential Specialized Code. 
  • All-Electric Pathway
    • Must meet minimum energy efficiency standards and not utilize fossil fuels.
  • Mixed-Fuel Pathway
    • Requires mitigation of any fossil fuel uses through:
      • Minimum efficiency requirements for space and water heating.
      • Solar development of the available on-site solar potential.
      • Pre-wiring and electrical service provision to the building to allow for future electrification.
The Stretch Code now has stricter requirements, and the Specialized Code is a new option for municipalities to require net-zero construction – with the option to offset fossil fuel use. While the new energy codes are currently under review with the Joint Committee on Telecommunication, Utilities, and Energy, these are the current regulations that DOER plans to release. 

Under state law, the Committee is required to issue a report on the proposed regulations. It is worth keeping an eye on this to see if there are any changes that the Committee recommends.

Law Clerk Nicholas Hanel co-authored this alert.