CALGreen Sustainable Construction

Overview

In the summer of 2023, California became the first state in the nation to mandate embodied carbon reduction in the building code. As of August 2023, the California Green Building Standards Code – Part 11, Title 24, California Code of Regulations, known as CALGreen, has been amended to limit embodied carbon emissions in construction, remodel, or adaptive reuse of existing building buildings.

CALGreen aims to reduce embodied carbon in new construction by providing three paths to compliance:

• Building Reuse (§5.105.2): Reuse at least 45% of an existing structure and its exterior. Building reuse is only permitted when the addition is less than twice the area of the existing building. Building reuse requirements are aligned with LEED v4 and v4.1 credit Building Life Cycle Impact Reduction. Compliance with this path can help projects achieve 1-3 LEED points.
• Whole Building Life Cycle Assessment (§5.409.2): Conduct a cradle-to-grave Whole Building Life Cycle Assessment (WBLCA) demonstrating 10% or greater reduction in embodied carbon when compared to a reference building of similar size and function, evaluated per the current California Energy Code. WBLCA requirements are aligned with LEED v4 and v4.1 credit Building Life Cycle Impact Reduction. Compliance with this path can help projects achieve 1-3 LEED points.
• Prescriptive Path – Product GWP Compliance (§5.409.3): Verify through the use of Environmental Product Declarations (EPDs) that installed products are below established thresholds for global warming potential (GWP). This path can support the achievement of various optional credits in the LEED v4 and v4.1 rating system, including:
  • Building Life Cycle Impact Reduction
  • Building Product Disclosure and Optimization – Environmental Product Declarations
  • Low Carbon Construction Materials Procurement

Who is impacted?

Effective July 1, 2024, all new construction, alterations and additions greater than 100,000 square feet shall comply with the new ordinance. Floor area is based on the combined area of new and existing construction. Effective January 1, 2026, the threshold changes to 50,000 square feet.

What does this mean?

The Embodied Carbon Requirements effective from July 1, 2024 apply to:

• K-12 schools 50,000 ft² or larger (project aggregate)
• Other non-residential buildings 100,000 ft² or larger. (project aggregate)
• In 2026, the non-residential project threshold will go down to 50,000 ft² (project aggregate).

Here’s How We Can Help

At Thornton Tomasetti, we take climate action seriously. Our current suite of services is already helping our clients work towards these ambitious new goals.

• Our Renewal practice makes it easier to reuse existing buildings through renovation, rehabilitation and retrofit of the existing structure and building envelope.
• Our Sustainability practice works with you to properly account for and reduce both operational and embodied carbon via Life Cycle Assessments and energy modelling.
• Our Structures practice remains at the forefront of building decarbonization by incorporating GWP thresholds into product specifications and through the use of innovative tools like Beacon, a Revit plug-in that helps engineers track and manage embodied carbon throughout all stages of design.

At each milestone of the project, our experts quantify the embodied energy and embodied carbon impacts of the structural systems we design. Our quantification is based on the estimated total quantities of structural materials at each stage and generally accepted coefficients for embodied energy and embodied carbon per material weight unit. Our Revit plug-in Beacon provides high level feedback and clear data visualization of a structural system’s embodied carbon performance to help clients evaluate various structural systems, from timber to steel to concrete or a hybrid.