Why is Title 24 required for ADUs?

Title 24 is required for ADUs because, under California law, an ADU is a dwelling unit — and California's Building Energy Efficiency Standards (Title 24, Part 6) apply to new dwelling units and to many alterations. A building department generally cannot issue a permit for new ADU construction without a registered CF1R (Certificate of Compliance) demonstrating the design meets the energy code.

The legal and practical reasons

• It's a dwelling unit. An ADU contains living, sleeping, cooking, and sanitation facilities, so it is treated as a residence for energy-code purposes — not as a shed or accessory structure.
• Permits depend on it. Plan check reviews the energy documentation alongside your architectural and MEP sheets. Missing or inconsistent Title 24 documentation is one of the most common reasons for an incomplete-submittal notice or a correction list.
• Statewide policy goals. California uses Title 24 to advance building electrification and lower energy use, which is why heat pumps and heat-pump water heaters are the current prescriptive baselines for new construction.

When it applies and when scope changes

Not every ADU project triggers the same depth of requirements:

• New detached ADUs face the most comprehensive requirements — full envelope, HVAC, water-heating, lighting, and potential solar provisions, with HERS verification of certain systems.
• New attached ADUs are also new conditioned space and are treated similarly to detached units for most measures.
• Garage and interior conversions are generally reviewed under alteration rules, which are typically narrower — solar usually does not apply, and insulation standards are triggered mainly where assemblies are actually altered — but a CF1R is still prepared and registered.

What this means for you

Think of the CF1R as the energy "passport" for your ADU: without it registered and submitted, the permit package is incomplete, and what the contractor installs later has to match what the document specifies.

Because the energy report dictates minimum HVAC efficiency, water-heater type, and lighting requirements, those choices flow directly into your mechanical, electrical, and plumbing sheets. The applicable code cycle and local amendments vary — confirm with your local building department. We prepare the registered CF1R as a +$240 add-on with your MEP plans so everything is consistent; see California ADU requirements for the bigger picture.