Boston Approves First-in-the-Nation Net Zero Carbon Rule

At 53-stories and 1.8-million-sq-ft, Boston's Wintrhrop Center is the world’s largest Passive House office building that also meets WELL Gold and LEED Platinum standards.

Photo courtesy Desimone Consulting Engineering

Boston’s first-in-the-nation net zero carbon zoning rule for new buildings passed Jan. 29 after failing to gain enough votes last year.

The city’s zoning commission approved the rule requiring most new developments to attain net zero carbon emissions when they open or the property owners will be fined—the most stringent carbon emissions rule for buildings in the nation, according to a statement released by Mayor Michelle Wu’s office.

The new zoning sets a net zero emissions standard for new projects filed after July 1, 2025, the city says. That includes 15 units or more, a minimum of 20,000 sq. ft., or additions of at least 50,000 square feet or more to existing buildings. It excludes small additions, renovations and adaptive reuse projects. Additionally, the measure provides life sciences labs until 2035, and new hospitals and manufacturing plants until 2045 to comply.

Last year a vote on the identical mandate fell one vote short of the seven votes necessary for a two-thirds majority. The measure passed this year after Wu fired former Zoning Commission chair Jay Hurley, a former leader of the Iron Workers Local 7 union, who voted against the measure. Wu also added two new members to her board. Hurley has alleged Wu fired him in retaliation for voting no.

Wu says the measure will help the city achieve its carbon-neutral goal by 2050.

“To protect families across our neighborhoods and keep our city running, we need urgent action to ensure resiliency for the safety and well-being of all Bostonians,” Wu said in the statement. “By embedding sustainability into new projects, we set Boston on a direct path towards a cleaner and healthier future for generations to come.”

Brian Swett, Boston’s chief climate officer, said in the statement that “addressing both operational and embodied carbon in new developments” tackles both emissions and helps “understand and reduce the carbon intensity of our building materials.”

Environmental advocate Rickie Harvey says the new zoning “addresses important carbon issues left out of the building codes allowing for offsets and procurements and considering embodied carbon, emissions from construction and life cycle analysis,” Harvey said in the city’s statement.

Harvey says the rule’s requirement for owners to report on embodied carbon is “crucial to correctly evaluating the costs and impacts of new construction.”

With Boston’s buildings comprising more than 70% of the community’s carbon emissions, the city is considering ways to reduce emissions and the impact on climate by changing operational performance requirements of new buildings, the city says. This can include reducing fossil fuels in favor of electrification and incorporating renewable energy sources, for example.

“We are proud to be a part of a community that challenges us all to imagine and build a better future," Joe Larkin, principal at Millennium Partners Boston, said in the city’s statement.

Millennium Partners developed Winthrop Center, which Larkin called “the most energy-efficient large-scale office building that can be built in a cold weather climate.”

But NAIOP Massachusetts, a chapter of the Commercial Real Estate Development Association, and other organizations are concerned the rule comes on the heels of other Boston ordinances and could increase development costs, the Boston Business Journal reports. The Building Emissions Reduction and Disclosure Ordinance (BERDO) adopted in 2024, for example, requires large buildings to reduce greenhouse gas emissions.

John Ferrante, CEO of the Associated General Contractors of Massachusetts, told ENR that AGC MA members can already “meet any sustainability requirements using cutting-edge materials, green technologies and sustainable building methods.”

Ferrante says AGC agrees with “the urgent need to enhance sustainable building development but are concerned about the impact additional requirements may have on an already down development market," but added that “we hope that, despite increased regulation, developers continue to see Boston as a good investment for their next commercial real estate project and AGC MA members will be ready to build it.”

Johanna Knapschaefer, ENR’s New England Special Correspondent, has been writing about trends in design and construction of buildings, bridges, tunnels and other infrastructure for more than a decade. She also profiles award-winning industry leaders and delves into broader construction issues such as workforce training, worker safety and health, climate change remediation and emerging offshore wind and tidal energy developments. Over the past two decades, her articles have appeared in Architectural Record, BusinessWeek, the Boston Globe, American Banker, Modern Metals, BusinessNH Magazine, Pittsburgh Magazine and many other publications. Johanna is fluent in Japanese, and taught English and academic writing in the Science and Engineering Department of Ritsumeikan University, Kyoto, while living in Japan for eight years.

When not writing, Johanna enjoys mountain climbing, singing and playing her Spanish guitar.