California Green Building Standards Code (CALGreen): Sustainability requirements for building design and construction

Background

CALGreen was developed as part of California’s efforts to reduce the environmental and climate impacts of buildings. The California Building Standards Commission (CBSC) began developing green building standards in 2007 in support of the greenhouse gas reduction objectives established under Assembly Bill 32, the California Global Warming Solutions Act of 2006.

The first CALGreen edition was published in 2008 and consisted of voluntary measures. Many of these provisions became mandatory with the 2010 edition, which took effect in January 2011, making CALGreen the first statewide mandatory green building standards code in the United States.

CALGreen complements other parts of California’s building regulations. In particular, mandatory building energy-efficiency standards are primarily established under the California Energy Code (Title 24, Part 6), while CALGreen addresses a broader range of environmental aspects of building design and construction.

Key Requirements

CALGreen organizes its green building requirements around five broad areas:

• Planning and design: Measures address site development and related environmental considerations, including electric-vehicle charging infrastructure and measures intended to reduce environmental impacts associated with development.

• Energy efficiency: CALGreen works alongside the California Energy Code, with additional voluntary measures available for projects and jurisdictions seeking performance beyond mandatory energy standards.

• Water efficiency and conservation: Requirements address indoor and outdoor water use and measures intended to reduce potable-water consumption.

• Material conservation and resource efficiency: Provisions cover issues such as construction and demolition waste, building materials and resource conservation. CALGreen also contains mandatory embodied-carbon reduction requirements for certain large nonresidential buildings.

• Environmental quality: Requirements address aspects of the indoor environment, including low-emitting materials and measures intended to improve conditions for building occupants.

Compliance and Enforcement

CALGreen is mandatory for projects falling within its applicable scope. Compliance is generally integrated into California’s normal building permitting, plan-review and inspection processes rather than operating as a separate environmental certification scheme.

Building departments and other enforcing agencies assess whether applicable CALGreen requirements have been incorporated into project plans and construction. The 2025 residential code, for example, requires a completed Residential Occupancies Application Checklist or another method acceptable to the enforcing agency to document conformity.

Current Status

The current edition is the 2025 California Green Building Standards Code, which became effective on January 1, 2026. It forms part of the wider 2025 edition of California's Title 24 building standards. Among the notable developments are stronger nonresidential EV charging requirements and the continued implementation of California's mandatory embodied-carbon provisions. For buildings under CBSC's authority, the threshold for the embodied-carbon requirements fell from 100,000 square feet to 50,000 square feet on January 1, 2026, broadening the number of large nonresidential projects covered.

Resources

• https://www.dgs.ca.gov/bsc/calgreen

• https://www.hcd.ca.gov/building-standards/calgreen/resources

• https://codes.iccsafe.org/content/CAGCGBSCNR2025/guide-to-the-2025-california-green-building-standards-code-calgreen-nonresidential