A Better City Conversations: Zero Net Carbon Zoning Initiative

Written by Yve Torrie, Director of Climate, Energy, & Resilience
Thursday, January 21, 2021 | SLIDESWATCH

On Thursday, January 21, A Better City hosted the team supporting the Boston Planning and Development Agency’s (BPDA) Zero Net Carbon (ZNC) Zoning Standard development process. Kate Dineen, Executive Vice President, and Yve Torrie, Director of Climate, Energy, and Resilience, at A Better City, welcomed John Dalzell, Senior Architect for Sustainability at the BPDA, and members of the ZNC consulting team, including Alejandra Menchaca and Colin Schless of Thornton Tomasetti, Jacob Knowles of the BR+A, Debra Perry of Cadmus (representing SolSmart), and Vincent Martinez of Architecture 2030. The purpose of the meeting was to provide members of the real estate community with an update on the ZNC Zoning Standard development process and how it fits with other climate priorities of the City and Commonwealth. Dalzell, Menchaca, Perry, and Martinez each presented on an aspect of the standard.

Dalzell provided an overview of Boston’s building emissions and goals, including that buildings represent 70% of Boston’s emissions and that Boston’s latest Climate Action Plan has identified early action items for achieving carbon neutrality. The BPDA is in the process of developing a zero net carbon standard to be included in Article 37 of the Article 80 large project review process. The framework for this standard includes: (1) low carbon buildings; (2) on-site renewable energy; and (3) offsite renewable energy, and a technical advisory group has been developed for each of these 3 pieces of the framework. Dalzell provided the example of Bunker Hill Community College which has utilized both low energy use and on-site renewable energy to achieve a very low carbon emissions intensity. The BPDA anticipates releasing a recommended standard in late winter or early spring. At that point the regulatory process will begin, which will involve zoning code development with both the BPDA Board and the Zoning Commission.

Mechaca, Schless, and Knowles provided an overview of low carbon buildings and the work of the technical advisory group to date. Their definition of a low carbon building includes:

  1. A low load envelope to limit energy loss;
  2. A high-performance HVAC that provides ventilation needed for indoor air quality but that is smaller and requires less heating;
  3. An all-electric system to replace gas or oil will reduce emissions by utilizing increasingly clean power from the energy grid.

They noted the importance of pairing these three elements from the outset of the design to reduce the size of equipment necessary and, therefore, the amount of energy needed. This ultimately reduces the amount of renewable energy that needs to be generated or procured. In their experience, this approach of right-sizing the envelope and systems to reduce energy consumption not only reduces energy needs but also allows for the building to be built at a cost premium of less than 1%. The team provided the example of the Chelsea Soldiers Home which has significant use needs (similar to a hospital) and has a 30% window-to-wall ratio with triple-pane glass, highly insulted envelope, ground source heat pump, and VRF, and a dual heat wheel. This building utilizes 70% less energy than those similar to it, and 50% less than the ASHRAE baseline. It was designed with only a $130,000 cost premium, which was more than covered by available utility incentives.

Boston has been recognized through a SolSmart designation for its efforts to reduce local barriers to solar energy and is utilizing SolSmart technical assistance in developing the ZNC standard. Perry, who supports management of SolSmart explained that net zero buildings integrate on-site renewable energy as much as possible and procure off-site renewable energy as necessary. On-site renewable energy is located on a building or adjacent property under the same ownership. To optimize on-site generation, it should be included early in design so that choices can be made to maximize solar opportunities. Through the process, it is necessary to consider technical limitations of the space, incentives and regulations, financial feasibility and market conditions, and how to encourage and accommodate innovation.

Martinez said the Renewable Energy Procurement technical advisory group is evaluating seven mechanisms as part of the renewable energy procurement component of the standard: (1) direct ownership, self-ownership, off-site project; (2) community renewables; (3) power purchase agreements, virtual power purchase agreements; (4) utility renewable energy contract, direct access to wholesale markets; (5) green retail tariffs, green pricing, green municipal aggregation; (6) renewable energy investment fund; and (7) unbundled renewable energy certificates. The group is assessing evaluation criteria, including impacts and additionality, durability and long term commitment, locality and local impact, assignment to building, electricity credits, incremental acquisition, grid management, environmental impact, inspirational and educational value, permanent financing, renewable generation sources, equity, and public health.


Following the presentation, attendees asked a series of questions, the answers to which are summarized below.

  • The zoning standard is intended to work in conjunction with BERDO.
  • The regulations do not define how reductions are achieved in every building, but instead set a target and provide options for ways to reach the target cost effectively.
  • The BPDA would like to see all buildings optimized for on-site generation but recognizes that while buildings like small residential may be able to meet all their energy needs, taller buildings will not.
  • Controls are key to making sure building design is translated into energy efficient operation.
  • Backup generation is likely to rely on fossil fuel usage in the near-term.
  • The City is considering development incentives but must balance those with other priorities, including affordability.
  • There are examples of net zero buildings across use types achieving cost parity or savings as compared with traditional design through thoughtful design, including load reduction strategies, and utilization of the utility and state incentives. Messaging that net zero is more expensive, particularly for affordable housing, is based on outdated information and it’s important for counter examples to be promoted.
  • It is challenging to operationalize embodied carbon standards but there is exciting progress, including on mass laminated timber, and the City is interested in engaging with folks on the topic moving forward.



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