What is Title 24?

Title 24 is the common name for California's Building Standards Code, and when people say it in the context of an ADU they almost always mean Part 6 — the Building Energy Efficiency Standards. It is the statewide energy code that sets minimum efficiency requirements for the building envelope, HVAC, water heating, lighting, and on-site solar for new dwelling units, including accessory dwelling units.

What Title 24 actually governs

Although "Title 24" technically covers the entire California building code (structural, fire, plumbing, electrical, and more), the energy-compliance document your plan checker is looking for is produced under Part 6. For a new ADU it typically addresses:

• Building envelope — insulation R-values for walls, floors, and ceilings, plus window U-factor and Solar Heat Gain Coefficient (SHGC) limits.
• Space conditioning (HVAC) — minimum efficiency for heating and cooling, with heat pumps as the current prescriptive baseline.
• Water heating — a heat-pump water heater (HPWH) baseline for most new dwelling units.
• Lighting — high-efficacy (LED) sources and required controls.
• Solar PV and storage-ready provisions — with several ADU-specific exceptions.

How compliance is documented

Compliance is demonstrated through the CF1R (Certificate of Compliance), a registered document prepared during design that proves your ADU meets the standards. There are two paths to get there:

• Prescriptive — every component individually meets a fixed minimum (R-value, U-factor, HVAC efficiency). Simple, but no trade-off flexibility.
• Performance — approved energy-modeling software shows your whole-building design performs as well as or better than a code-compliant baseline, letting you trade a weaker spot in one area for a stronger one elsewhere.

Construction is later verified with the CF2R (Certificate of Installation) from your contractors and, where required, the CF3R (Certificate of Verification) from an independent HERS rater.

Why it matters for your project

California revises these standards on a three-year cycle — the 2022 code and the 2025 code (effective for permit applications submitted on or after January 1, 2026) are the cycles most ADU owners deal with today. The applicable code cycle and any local amendments vary by jurisdiction, so confirm the current requirements with your local building department. We prepare the registered CF1R as a Title 24 add-on (+$240) alongside your MEP plans so the energy report and the mechanical, electrical, and plumbing sheets are coordinated from the start. See Title 24 Reports for details.