Event Recap: The City of Boston's Draft Zero Net Carbon Standard: Updated Zoning for New Construction Buildings


On Monday, October 18th, A Better City hosted a meeting to learn more about the City of Boston's Zero Net Carbon (ZNC) Building Zoning Initiative, which is designed to advance new construction practices to meet the goal of carbon neutrality by 2050. On the evening of October 20th, the Boston Planning and Development Agency (BPDA) and their ZNC consulting team held a two-hour public meeting on the same topic. During the public meeting, the BPDA released four draft reports from the consultant-led Technical Advisory Groups (TAGs) with recommendations for Low Carbon Buildings; On-Site Renewable Energy; Renewable Energy Procurement; and Embodied Carbon.

The objective of this updated zoning policy is to establish a ZNC Building Emissions Performance Standard for new construction that includes lowering the threshold to 20,000 square feet (small and large project review buildings), increasing the LEED outcome to LEED Gold, and updating the Article 37 Green Buildings and Climate Resiliency review process.

Over the last year, four TAGs have met regularly to develop recommendations for key sections of this updated zoning policy. Below is a summary of their recommendations.



The Low Carbon Building TAG was tasked with establishing building emission targets. The recommended pathways include:

  • A carbon emissions reduction target for all building typologies of 40% per project compared to an ASHRAE 90.1-2013 baseline OR the Massachusetts stretch code baseline.
    • Important exceptions include Healthcare facilities that will require a 30% carbon emissions reduction target and buildings committed to Passive House certification, among others.
  • Carbon emission intensity (CEI) targets for 10 different building typologies in addition to all-electric site energy use intensity (EUI) targets.
  • Carbon emissions factors that are consistent for BERDO and ZNC zoning.

Yve Torrie and representatives from five A Better City member companies were in this group.



The On-Site Renewable Energy TAG was tasked with setting minimum generation standards for on-site renewable energy to maximize south facing solar opportunities on building roofs, facades, and sites, and design roof layouts to maximize free space. Buildings will be required to have a solar energy system that is:

  • Equal to or greater than 50% of the building roof area that is flat or oriented between 110 and 270 degrees of true north.
  • 90% of parking structure decks that are uncovered.
  • 50% of surface parking areas.
  • Exceptions include mechanical/structural restrictions, over 50% shading, building preservation, and electric utility system constraints, among others.

Representatives from two A Better City member companies were in this group.



The Renewable Energy Procurement TAG was tasked with determining acceptable renewable energy procurement options and recommended:

  • Direct Ownership / Self-owned, off-site project
  • Green Municipal Aggregation / Green Retail Tariffs / Green Pricing
  • Unbundled Renewable Energy Certificates / Credits (RECs)
  • Power Purchase Agreements (PPAs) / Virtual Power Purchase Agreements (VPPAs)
  • Utility Renewable Energy Contract / Direct Access to the Wholesale Markets
  • Renewable Energy Investment Fund

Generation sources can be solar photovoltaic, solar thermal electric, wind energy, small hydropower, marine or hydrokinetic energy, and geothermal energy. Existing district energy plants can also accept all MA Class I renewable energy sources including landfill, methane, anaerobic digester gas, and eligible biomass fuel.

Minimum requirements for off-site renewable energy procurement include:

  • The generator must qualify as a MA Class I generator
    • An important exception is that wind or solar generators outside ISO-NE are allowed for PPAs when the generators are located in regions where the carbon emissions of the electric grid are higher than those of ISO-NE.
  • The purchase commitment must be lasting and verified each year.
  • RECs must be retired on behalf of the ZNC building.

Yve Torrie and representatives from three A Better City member companies were in this group.



The Embodied Carbon TAG was tasked with identifying embodied carbon actions and introducing best practice standards. Embodied carbon considers all the carbon emitted in a building’s life cycle from raw material extraction, transportation, manufacturing, construction, demolition, and landfill, while operational carbon is emitted during the use and maintenance of a building. To reach net zero, a building must minimize its total carbon (operational plus embodied carbon) over its life cycle, and offset any remaining carbon.

Recommendations included:

  • Policy
    • Update the Climate Action Plan with embodied carbon goals and strategies
    • Develop a building use and deconstruction ordinance
    • Require LEED embodied carbon-related/life cycle assessment credits
    • Require whole-building life cycle analysis in zoning/permitting processes
    • Collaborate with the State on reducing embodied carbon
  • Practice
    • Pilot programs and demonstration projects to minimize embodied carbon
    • Consider a wide range of incentives to encourage embodied carbon reduction
    • Develop an advisory group to the City
  • Awareness
    • Recognize best practices for embodied carbon in new construction
    • Build City capacity and expertise
    • Expand local workforce and skill specification
    • Collaborate with the architecture, engineering, and construction communities

Representatives from two A Better City member companies were in this group.



Throughout the fall of 2021, the BPDA will develop the regulatory documents to support these TAG recommendations. In early winter 2021/2022, the BPDA plans to present these materials to the BPDA Board of Directors for their consideration. With BPDA Board approval, they will then petition the Boston Zoning Commission for adoption of these amendments. There are opportunities for stakeholder engagement throughout this process.

Comments on the draft reports from the TAGs are due to BPDA by November 19, 2021. A Better City will be providing comments; please feel free to send any comments or questions to Yve Torrie. Comments can also be submitted directly online using the comment form at the bottom of the webpage or to John Dalzell at: John.Dalzell@boston.gov

The BPDA public meeting video recording from October 20, 2021 can be found here.

The presentation from the BPDA public meeting on October 20, 2021 can be found here.

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