On July 31, 2023, Boston Mayor Michelle Wu signed an executive order ending the use of fossil fuels in new construction and major renovations of city-owned buildings. Although city buildings comprise a small percentage of overall carbon emissions in Boston, the new executive order aligns with larger efforts to decarbonize both publicly and privately owned buildings throughout Boston.

The executive order covers both new city buildings and renovation projects affecting 75% or more of a city building's square footage. Covered buildings and projects will require heating, ventilation, air conditioning, hot water, and cooking systems that do not use fossil fuels. While municipal emissions make up only 2.3% of all carbon emissions in the city, over 70% of those emissions come from buildings. The executive order takes effect immediately but doesn't apply to projects currently in procurement, design, or construction.

Mayor Wu's action applies only to city-owned buildings for a reason: under current state law, municipalities are preempted from passing across-the-board fossil fuel bans. So, the city is limited, for now, to eliminating the use of fossil fuels in its own buildings. A 2022 climate bill signed by then-Governor Charlie Baker, “An Act Driving Clean Energy and Offshore Wind,” allows 10 municipalities to participate in a pilot program to prohibit fossil fuel connections locally. Priority will be given to the first 10 communities who filed home rule petitions to participate, of which Boston is not one.

Boston does have a city-wide plan to reach net-zero building emissions by 2050, with the details of that plan still to be determined. Thus, as building owners and developers plan for how they'll comply with those emissions reduction requirements, the city's own elimination of fossil fuels in new construction and major renovations—through Mayor Wu's recent executive order—could provide a useful model for decarbonization in the private building sector in the coming years.