California becomes first state to adopt mandatory measures in building code to reduce embodied carbon

Applicable to most large buildings, changes to building code developed via the CALGreen Carbon Reduction Collaborative bring new tools to counteract climate change.

Sacramento, California– Against the backdrop of this summer’s devastating series of climate crisis events, the State of California adopted new codes which will reduce a major contributor to global warming.

At their Wednesday, August 2, 2023, meeting, the California Building Standards Commission (CBSC), voted unanimously for two building code changes to limit embodied carbon emissions in the construction, remodel, or adaptive reuse of commercial buildings larger than 100,000 sq feet and school projects over 50,000 sq ft. These changes go into effect on July 1, 2024, statewide.


In making these changes, California becomes the first state in the nation to set general code standards that require the reduction of embodied carbon emissions in the design and building process applicable to both commercial buildings and schools. Embodied carbon refers to greenhouse gas emissions arising from building materials over their life cycle, which includes manufacture, transportation, installation, maintenance, decommissioning, and disposal.

“It can take up to 80 years to overcome embodied carbon’s impact through strategies that reduce energy usage or operational carbon; the planet doesn’t have that time,” said AIA California President Scott Gaudineer, AIA. “Today’s actions by the Division of the State Architect, led by California State Architect Ida Clair, AIA, and the California Building Standards Commission led, until very recently by Executive Director Mia Marvelli, AIA, codify a cultural shift: to meet decarbonization timelines set by California law, embodied carbon must be reduced in addition to operational carbon.”

A 2019 Code Change Petition submitted by AIA California was instrumental in leading to the foundation of the CALGreen Carbon Reduction Collaborative by DSA and CBSC. The collaborative is a group comprised of representatives of several California State agencies and non-governmental groups.

The code additions are amendments to the 2022 California Green Building Standards Code (CALGreen), Part 11, Title 24. They provide three alternative compliance paths that can be elected by design professionals to meet the new standards. The carbon reductions build on California’s Buy Clean California Act (BCCA) of 2017, extending the scope of projects covered significantly, and adding to the list of covered materials to include concrete. The compliance paths include one based on reuse of at least 45% of an existing structure; one based on specification of materials that meet specified emission limits, and a third performance-based path that allows use of a Whole Building Lifecycle Assessment analysis.

To develop these amendments, AIA California “worked directly with both key state agencies and a wide range of other stakeholders to ensure that the methods, metrics, criteria, and process is both significant and attainable,” noted Michael Malinowski, FAIA, who led the effort for the organization. “In their final form, these standards will be easily achieved for the large-scale projects they will apply to.”

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AIA California worked with partners and organizations like the New Buildings Institute (NBI), RMI, U.S. Green Building Council (USGBC), Architecture 2030, California Construction and Industrial Material Association, Carbon Leadership Forum (CLF), ClimateWorks, EcoBuilding Network, Energy Solutions, Greenmetry, StopWaste, Natural Resources Defense Council (NRDC), representatives of the concrete industries, SF Environment, and many others to vet technical aspects of the amendments and bring them to fruition.

“The American Institute of Architects California has been working for a number of years to help California move forward with decarbonization of our building stock, which contributes approximately 40% of our state’s greenhouse gas pollution,” said Malinowski. “Using the building code in this way is important in shifting ‘business as usual’ across the building industry to also address climate action.”

In the coming months, AIA California will be developing and hosting programs to expand awareness and implementation of the code changes for design professionals and our collaterals and partners in the building industry and beyond.

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