First City In America With Net-Zero Carbon Building Requirements

Boston has become the first city in the US to mandate that most large new buildings achieve net-zero carbon emissions from the day they open. This regulation, within amended zoning codes, passed in January 2025, and is considered the most stringent building emissions rule in the United States. The new requirement marks a significant step in Boston’s climate agenda under Mayor Michelle Wu.

Scope and Requirements

The new net-zero standard applies to:

• New construction projects filed after July 1, 2025,
• Buildings with 15 or more residential units,
• Buildings of at least 20,000 square feet,
• Additions of 50,000 square feet or more to existing structures.

Excluded from the policy are renovations, additions under 50,000 square feet, and changes of use, which is intended to encourage large-scale reuse projects that integrate energy efficiency upgrades.

Compliance and Enforcement

Developers must demonstrate compliance with net-zero requirements during the existing development review process. Projects can meet the standard by:

• Reducing energy use,
• Minimizing reliance on fossil fuels,
• Increasing electrification and use of renewable energy sources.

All projects, regardless of size, must report on embodied carbon—the total greenhouse gas emissions generated to produce building materials. Large projects are also required to conduct a life cycle assessment of embodied carbon.

Phased Approach for Certain Sectors

Recognizing the unique energy and ventilation needs of specific building types, the policy introduces a phased compliance schedule:

• Life sciences laboratories have until 2035 to comply,
• Hospitals and general manufacturing facilities have until 2045,
• Background and Rationale

Buildings are responsible for nearly 71% of Boston’s carbon emissions. The city’s leadership believes that by targeting operational performance of new buildings, it can significantly reduce its climate impact. The newly effective zoning amendment builds upon existing state and city policies, including the Specialized Stretch Energy Code and the Building Emissions Reduction and Disclosure Ordinance (BERDO), both of which set performance thresholds for energy and emissions.

Boston is among at least 13 U.S. cities with a building performance standard in place as of early 2024, but its immediate net-zero requirement for new large buildings is seen as a national first.

Boston’s net-zero zoning law sets a new national benchmark for urban climate policy, aiming to drastically cut emissions from the city’s largest source—its buildings. Through stringent standards, phased implementation for complex sectors, and integration with broader climate initiatives, the city seeks to lead by example in the transition to a decarbonized built environment.

More information is available here.

Image: Pixabay.com

David Shiller

David Shiller is the Publisher of LightNOW, and President of Lighting Solution Development, a North American consulting firm providing business development services to advanced lighting manufacturers. The ALA awarded David the Pillar of the Industry Award. David has co-chaired ALA’s Engineering Committee since 2010. David established MaxLite’s OEM component sales into a multi-million dollar division. He invented GU24 lamps while leading ENERGY STAR lighting programs for the US EPA. David has been published in leading lighting publications, including LD+A, enLIGHTenment Magazine, LEDs Magazine, and more.

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