Finch Cambridge is the largest new multifamily affordable housing development in Cambridge in 40 years and one of the first large-scale multifamily developments to achieve Passive House certification in Massachusetts. Photo by Robert Umenhofer | Courtesy

Multifamily developers will be encouraged to build Passive House-certified buildings beginning in January 2023 in proposed new regulations designed to cut carbon emissions, but natural gas hookups won’t be banned.

“We’ve seen a tremendous growth of this design approach and the growth of the industry as well with over 130 firms in Massachusetts,” said Paul Ormond, a state Department of Energy Resources energy engineer.

The DOER held a virtual briefing today on proposed new building codes to meet the state’s goal of cutting greenhouse gas emissions statewide by 50 percent from 1990 levels by 2030.

Massachusetts communities can adopt a “specialized opt-in” building code in the wake of the climate change bill signed into law last March by Gov. Charlie Baker. The proposed code provides even more aggressive energy savings requirements than the existing stretch code in place in 299 communities, which is also being updated.

The proposed regulations do not allow communities to ban fossil fuel-burning building systems, something development groups feared would make building new housing unaffordable. A legislator who sponsored the bill recently questioned whether the Baker administration was diverting from the goals of the new law.

Under the proposed specialized code, multifamily buildings up to five stories would be required to use Passive House designs beginning in January 2023. Requirements for mid- and high-rise multifamily buildings would begin in January 2024.

The Passive House technique includes tight building envelopes and robust ventilation systems to limit heat and cooling requirements. It has been used in construction or design of more than 6,500 housing units in Massachusetts since 2017, according to state Department of Energy Resources officials.

The opt-in code would not require all-electric systems, but require that new buildings be constructed with pre-wiring to accommodate non-fossil fuel systems.

Commercial buildings would be pushed toward more energy-efficient designs under the specialized opt-in code. Developers would be required to include solar panels on available roof space and pre-wire buildings for electric HVAC systems.

And the opt-in code would require single-family homes to be built to Passive House or Home Energy Rating System (HERS) level 42 standards, including a combination of fossil fuel systems and required solar arrays if feasible.

Proposed changes to the existing stretch code include use of low-carbon concrete in commercial buildings with curtain wall construction, and additional requirements for air rightness, windows, ventilation and thermal bridging.

DOER has until the end of 2022 to finalize the new regulations. Officials said they will schedule regional public hearings between Feb. 28 and March 9 and are accepting public comments at stretchcode@mass.gov.