Building Performance Standards Implementation: Emissions Factors and Accounting for Cambridge's Net-Zero Building Emissions Policy

The City of Cambridge hired Synapse to make recommendations to inform amendments to and rulemaking under Cambridge’s Building Energy Use Disclosure Ordinance (BEUDO). Our work focused on emissions from energy use and evaluation of potential criteria for carbon offset purchases. The amendment will regulate direct and indirect greenhouse gas emissions associated with energy use in medium and large-sized commercial and multifamily buildings. As part of this work, Synapse conducted extensive stakeholder engagement to review various aspects of the building emissions policy. Synapse’s research, analysis, and recommendations will help prepare local stakeholders to ensure buildings decarbonize in alignment with the policy.

Synapse identified data sources and methods for estimating historical and future emission factors for energy use in buildings. We evaluated various approaches, weighing the pros and cons, and identified best practices to inform the regulations development process. Our review encompassed marginal, average, residual, and time-of-use emission factors; grid geography and topology effects; historical and future emission factors; and effects of state renewable portfolio standards on the emissions accounting. We also applied best practice methods to allocate emissions to the concurrent outputs from co-generation plants, such as steam, hot water, chilled water, and electricity. Based on the results of this research, Synapse developed recommend emission factors for grid electricity, district steam, and combustion fuels, including a forecast of electricity emission factors under the Massachusetts renewable portfolio standard and related policies.

To support our review of emission factors, Synapse also evaluated proposed amendment language that would allow building owners to purchase carbon offsets in lieu of directly reducing building emissions. We identified risks associated with using carbon offsets and eligibility criteria that might improve the likelihood that carbon offsets create environmental benefits.