BOSTON (SHNS) – The Baker administration on Tuesday rolled out the state building code changes that it hopes will encourage builders to shift away from fossil fuel heating in favor of electrification, including a new municipal opt-in net-zero stretch energy code that does not eliminate gas-heated buildings but would hold them to a higher efficiency standard.

Updating the existing stretch code and creating a new net-zero specialized stretch code for cities and towns to adopt is one of the more technical but meaningful steps Massachusetts is planning to take to be net-zero by the middle of the century. Residential and commercial building energy consumption was responsible for about 27 percent of the state’s greenhouse gas emissions in 2017.

The new net-zero code is required by last year’s climate law to be in place by the end of 2022 and was one of the more controversial aspects of the law, which Gov. Charlie Baker initially vetoed as developers warned that a net-zero stretch code would make the construction of new homes cost-prohibitive.

“What we are proposing today would have a significant impact on both our greenhouse gas emissions as well as the costs for residents in these buildings. Collectively, we’re looking at over $21 billion in lifecycle costs,” DOER Commissioner Patrick Woodcock said Tuesday. He added, “I’d also note, we are extremely mindful that we want to ensure that this is not only providing lifetime costs and greenhouse gas savings, but it also allows our housing industry to utilize the most cost-effective solutions.”

A driving consideration in the administration’s proposal is limiting harmful emissions by pursuing broad electrification as a means to meet the requirement that emissions be at least 50 percent below 1990 levels by 2030 and at least 85 percent lower than 1990 levels by 2050 with other strategies deployed to achieve a net-zero standard. More than half of the emission reductions needed to meet the 2050 commitment will have to come from personal vehicles (transitioning from gas- to electric-powered cars) and residential space heating, according to the Baker administration.

The average Massachusetts home using natural gas generates about 120 pounds of carbon dioxide emissions a month to make hot water, Maggie McCarey, director of DOER’s Energy Efficiency Division, said. Homes that use electric heat pumps now generate about 43 pounds of CO2 to make the same hot water each month and heat pump heated buildings are expected by 2050 to generate about two or three pounds of CO2 to make a month’s worth of hot water, she said.

McCarey said DOER conducted research “to explore and understand the least cost path to decarbonizing our buildings so that we can maintain a vibrant economy, meet our state’s needs for new and affordable housing, while also addressing our climate mandates.” She said the analysis looked at 12 different types of buildings and their specific needs, which “results in a proposal that optimizes costs and results in significant cost-effective emissions reductions.”

Woodcock said DOER’s proposed update and new specialized stretch code target new construction, which adds about one percent to the square footage of the state’s “built environment” each year. The commissioner said DOER estimates that about 27 percent of the building space that will exist in 2050 has not yet been built.

“That means that we need to move forward with integrating the most cost-effective climate solutions into new construction today and ensure that those buildings are 2050 compliant,” he said.

The Baker administration is also banking on the integration of electrification into new buildings having a “spillover” effect of making another key part of the state’s climate policy — retrofitting existing buildings to be more efficient and use cleaner technology — cheaper, Woodcock said.

Sen. Michael Barrett, the co-chairman of the Joint Committee on Telecommunications, Utilities and Energy who has closely tracked the Baker administration’s development of a specialized stretch code, told the News Service that he is “disappointed” with the initial proposal and is hopeful that his concerns could be addressed before the code changes take effect at the end of the year.

“It seems that a lot of additional natural gas infrastructure is going to be put in the ground in both communities that adopt the new specialized opt-in code and in communities that stick with the 2010 stretch energy code,” he said. “These are assets, fossil fuel assets, that we will need to walk away from before 2050. So that means we’re going to have to abandon them before the end of their useful life.”

Building Code Options

Since 2010, municipalities have had two options when it comes to picking a building code: they could adopt the state’s base energy code or, as 299 of the state’s 351 cities and towns have done, choose to use the stretch energy code first created in the Green Communities Act of 2008 as a requirement to become a Green Community. The code is meant specifically to “minimize, to the extent feasible, the lifecycle cost of the facility by utilizing energy efficiency, water conservation and other renewable or alternative energy technologies.”

Now, cities and towns will have a third option, one that DOER referred to as a “climate-focused” specialized stretch code, which the 2021 climate roadmap law requires. DOER is also proposing updates to the base code that 52 municipalities rely on and to the more common stretch code. Unless a city or town decides to adopt the new specialized stretch code, it will continue to use whichever code it has adopted along with the latest updates.

Here’s what would change for low-rise residential buildings (one- and two-family homes, townhouses, and low-rise multi-family homes) under the stretch code updates and the new opt-in specialized stretch code proposed Tuesday by DOER:

  • If a community sticks with the existing stretch code and the proposed updates, new buildings would no longer be held to a Home Energy Rating System (HERS) Index of 55. Instead, buildings that use electric heating would be required to have a HERS rating of 45 or better and homes that use fossil fuels would be held to a standard of HERS 42. The average new home built in Massachusetts in 2020 scored a 51 on the HERS Index and a truly net-zero home would register a HERS score of 0.
  • If a community adopts the new specialized stretch code, new electric heat buildings would simply have to meet the HERS 45 standard. New buildings with fossil fuels would have to meet the HERS 42 standard, have solar on unshaded and available roof areas, and at least be pre-wired to accommodate further electrification, especially electric vehicle charging. Buildings could also comply by meeting a “passivehouse” standard and being pre-wired for EV charging.

For a new home using an electric heat pump to reach the HERS 42-45 range, “better air sealing and ventilation is all that is needed” from builders, DOER said. For gas-heated homes, achieving a HERS rating of 42 or better “requires some combination of triple-glazed windows, improved insulation, better air sealing and heat recovery ventilation,” the department said.

Similar changes meant to encourage builders towards electrification would apply under both scenarios for commercial buildings with more complicated pathways by which buildings can comport to the stretch code or the specialized stretch code.

Next Steps

DOER will accept public comments on its proposed changes to the stretch energy code and on its draft specialized opt-in stretch code until 5 p.m. on March 9. The department said emailed comments should be sent to and include the subject line “Stretch Code Straw Proposal Comments.” Written comments can be sent to the attention of Nina Mascarenhas at DOER, 100 Cambridge St., Suite 1020, Boston, MA, 02114.

The department also plans to hold a handful of hearings around the state on the proposals, as is required by the 2021 climate law. DOER said at least four hearings will be held in late February or early March and that the feedback from those sessions will inform the drafting of specific code language that would be subject to regulatory public hearings in the summer.