Event Recap: Boston’s Zero Net Carbon Zoning for New Construction Working Session

Written By: Isabella Gambill, Senior Policy Advisor on Climate, Energy, & Resilience

As you may recall from an earlier A Better City Conversation in January 2021, the Boston Planning and Development Agency (BPDA) is in the process of developing a Zero Net Carbon (ZNC) Zoning standard for new construction in Boston. The ZNC standard is intended to complement the recently signed Building Emissions Reduction and Disclosure Ordinance (BERDO 2.0) which targets building emissions in existing buildings. Both policies will work together to help decarbonize Boston’s building sector (our city’s largest source of emissions) and ensure that we realize Boston’s commitment to net zero emissions by 2050.

Over the last year, four Technical Advisory Groups (TAGs) have met to develop recommendations on: 1. low carbon buildings; 2. on-site renewable energy; 3. renewable energy procurement, and 4. embodied carbon. Comments on these recommendations were due on November 19th.

A Better City submitted a robust set of comments based on member feedback. To ensure members had the opportunity to speak directly with the BPDA about their concerns and the challenges they anticipate, A Better City hosted a working session with John Dalzell, Senior Architect for Sustainable Development at the BPDA on Tuesday, December 14th, 2021.  

John Dalzell gave a presentation that began by clarifying the role of ZNC zoning in the context of other city-level regulations, procedures, and policies, and provided additional context on how the ZNC standard would interact with BERDO 2.0 (a key alignment concern for ABC members). Although considerable confusion has resulted from the concurrent policy development of BERDO 2.0 and ZNC zoning, the ZNC zoning’s focus is to establish targets for low carbon buildings (operational carbon emissions), onsite renewable and offsite renewable energy procurement in new construction. 

John Dalzell then provided a summary of all the comments received on the TAG recommendations:

  • Most are very supportive of ZNC policy and action.
  • Most support LEED Gold, with some supporting LEED Platinum.
  • Need to improve alignment of ZNC and BERDO 2.0 building typologies and uses.
  • Explain compliance from planning to post occupancy and BERDO 2.0 reporting.
  • Explain how differences between modeled performance and operational performance may be resolved.
  • Clarify how performance standards are calculated, including reference standards.
  • Clarify how ZNC Zoning will fit with other state policies (including the anticipated DOER municipal opt-in stretch code as per climate bill S.9, the Clean Heat Commission CAPS, and the update to the current stretch energy code within DOER).
  • Define methodology for calculating emissions factors and review local distributed generation.
  • Exempt emergency backup generation.
  • Expand and incentivize embodied carbon strategies.
  • Establish the ZNC Advisory Group to refine standards and guide steps ahead.
  • Professionals employed by building owners should be considered as data verifiers.



  • Moving from a ZNC Standard to BERDO 2.0: Members continued to express confusion about how to comply with BERDO once constructed. John Dalzell said that once constructed, a building will need to adhere to a ZNC standard under BERDO.
    • If new building include gas, does that mean they will automatically pay an Alternative Compliance Payment under BERDO 2.0?
    • Is emergency backup generation exempt from both BERDO 2.0 and the ZNC standard? Yes. As per BERDO 2.0, this is exempt until at least 2030.
  • Performance as a Hard Target: Some members highlighted concerns about the treatment of building energy performance as a hard target. They said the numbers referenced in the ZNC standard are significantly lower than average (for example, in office space, the energy performance target included is less than half the average for operational offices in Boston currently). John Dalzell clarified that the energy performance “target” is intended to serve more as a goal for performance by building typology, rather than a hard maximum.
    • It was further noted by members that where we set these targets matters. It will be hard for developers to be comfortable with the targets referenced in ZNC zoning until there are real examples of operational and occupied buildings matching modelled performance.
    • The ZNC standard language needs to be extremely clear on energy performance targets acting more like guidelines. These must also be mindful of especially hard-to-decarbonize building typologies.
  • Modeled Vs. Operational Data: A common piece of feedback in both written comments and discussion was the need for more operational, real-world examples of buildings that can comply with the proposed ZNC standard. Although permitted buildings may comply in modeling data put forward to the BPDA, the performance of a building post construction can be quite different. John Dalzell recognized a need to clarify that there is enough flexibility in anticipated regulations to adjust to best practices and operational performance vs. modeled building performance. He said the carbon emissions targets will be continually reviewed and dynamically updated over time.
    • Members said that the actual operational examples of commercial zero net carbon buildings are fairly limited in Boston. John Dalzell agreed to provide examples of buildings that have been recently constructed or are in the permitting stage at BPDA.
    • Where would the discrepancies between design/modeled calculations of performance vs. actual building performance once operational and occupied be captured? John Dalzell clarified that any discrepancy between modeled vs. actual performance would be accounted for in annual BERDO 2.0 reporting.
  • Customized Emissions Factors: Despite the request to have more customized emissions factors for localized generation sources, the BPDA will continue to use emissions factors provided by ISO-NE and DOER, to ensure consistency.
  • Electricity Grid: Members expressed concern about the electricity grid and what happens if it does not decarbonize quickly enough. They asked for clarity about this in the ZNC language.
  • Buildings in Design and Permitting Currently: Concern was expressed about buildings that are already in the design and permitting stage with BPDA but have not been built yet. They wondered if there was a potential for a building that have been approved in the design phase by BPDA, but once built – and assuming the ZNC zoning has been approved - the building is immediately out of compliance. It was clarified that any building that has already received permitting from BPDA would not have to re-apply once ZNC zoning goes into effect.
  • ZNC Advisory Group: Without sufficient examples of performing buildings, members expressed concern that the ZNC standard cannot solely be based on modeled examples, and that once you incorporate complications associated with lending and tenant negotiations, this will become even more challenging to implement. To help address such concerns, John Dalzell said a ZNC Advisory Group will be established to help guide the regulatory process and implementation of the ZNC standard. He hopes members like ABC’s member organizations will participate.
  • Renewable Energy Investment Fund: Clarity was sought on the role of the ZNC’s referenced Renewable Energy Investment Fund, and how that would interact with BERDO 2.0s Equitable Emissions Reduction Fund. John Dalzell clarified that the ZNC’s Renewable Energy Investment Fund is intended to be a local procurement vehicle that could in theory support community solar projects and other regional initiatives beyond buying renewable energy credits. The role of and disbursements from the Renewable Energy Investment Fund will be something to be further developed in the regulatory process and with additional stakeholder input.


The next steps include finalization of the TAG recommendation reports based on public comments received, followed by a draft of the ZNC regulations based on these recommendations and comments. Once the draft is made public, anticipated this winter, further focus groups and stakeholder groups will be held. After a public comment period, the updated draft will be presented to the BPDA Board of Directors for approval, and finally to the Zoning Commission. Once approved by the Zoning Commission, the ZNC standard would be signed into law by the Mayor and become effective immediately upon signing.

For any questions/comments on the ZNC Zoning standard, please contact Yve Torie.






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