Boston Enforces Net-Zero Emissions Standards for New Buildings and Major Renovations

Key Takeaways

The Boston Zoning Commission mandates net-zero carbon emissions for large new buildings starting July 1, 2025.
This regulation applies to buildings with 15 or more units, a minimum of 20,000 square feet, or significant expansions of existing structures.
Exemptions include small renovations and specific facility types like hospitals and labs, which have extended compliance timelines.

New Zoning Regulations for Carbon Emissions in Boston

The Boston Zoning Commission has officially adopted an amendment to the city’s zoning code, aimed at reducing carbon emissions from large new buildings. As announced by Mayor Michelle Wu, the new regulation establishes a net-zero carbon emissions standard that will take effect for building project filings submitted after July 1, 2025. This requirement targets new construction projects that comprise 15 residential units or more, have a minimum square footage of 20,000 feet, or involve expansions of at least 50,000 square feet to existing buildings.

Buildings currently account for nearly 71% of Boston’s carbon emissions. By implementing stricter operational performance criteria for new buildings, the city aims to significantly reduce these emissions and its overall impact on climate change. Compliance with the new standards can be achieved through various strategies, including minimizing energy consumption, decreasing reliance on fossil fuels, and increasing the use of electrification and renewable energy resources.

The amended zoning code mandates that all projects demonstrate adherence to the net-zero emissions standard during the development review process. This includes both large and small projects, which must report on embodied carbon. Larger projects will also be required to undergo a comprehensive life cycle assessment of embodied carbon.

These amendments align with updated state building codes and municipal ordinances such as the Specialized Stretch Energy Code and the Buildings Emissions Reduction and Disclosure Ordinance (BERDO). Notably, by early 2024, Boston joins the ranks of at least 13 U.S. cities that will enforce building performance standards, which obligate building owners to achieve defined energy efficiency and emissions goals.

BERDO, which initiates its first compliance period this year, applies to nonresidential buildings of 20,000 square feet or more, residential buildings with at least 15 units, and multiple buildings across tax parcels that collectively meet these size specifications. Buildings under this ordinance are required to provide annual reports regarding energy and water usage, verify these reports through third-party assessments, and comply with established annual emissions limits.

Additionally, nonresidential structures that are 35,000 square feet or larger must meet designated emissions compliance benchmarks starting this year. There is a forthcoming compliance period for buildings sized between 20,000 and 34,999 square feet, set to begin in 2030.

The newly approved net-zero carbon zoning policy, however, does not apply to renovation projects, additions under 50,000 square feet, or changes of use. This approach promotes larger-scale reuse projects that include energy efficiency upgrades, as highlighted in the press release. Furthermore, the policy acknowledges distinct energy and ventilation needs of certain facilities—hospitals, general manufacturing sites, and laboratories—allowing them longer timelines to achieve compliance. New laboratory constructions will have until 2035 to meet net-zero emission standards, while new hospitals and general manufacturing structures will have deadlines extended to 2045.

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