Title 24 energy compliance for ADUs

Almost every new ADU in California needs Title 24, Part 6 energy compliance documents before the building department will issue a permit. The paperwork proves the design meets the state's Energy Code: insulation, windows, heating and cooling, water heating and, for some ADUs, solar.

Your ADU type decides the rules

The Energy Code doesn't have a separate ADU category. It treats an ADU as a new building, an addition or an alteration, depending on how it's built:

• Detached, newly built (including one joined only by a breezeway): treated as a newly constructed building, so solar PV is required.
• Attached to the house, a garage or storage conversion, or built over or beside an existing detached garage: treated as an addition. No solar requirement.
• Converting space that's already heated or cooled: treated as an alteration.

Two ways to comply

You can meet every listed requirement for your climate zone (the prescriptive path), or model the whole building in approved software and show it performs at least as well as the code's baseline (the performance path). The performance path lets you trade, for example, a more efficient heat pump against slightly less wall insulation.

What the building department receives

The design-stage document is the CF1R, the Certificate of Compliance. For most new ADUs it must also be registered with an approved data registry before the permit, because the design includes items a certified rater has to verify on site.

Details that often trip ADUs up

• Detached ADUs must meet whole-dwelling ventilation (indoor air quality) rules.
• An attached ADU can't share the main house's existing forced-air heating system.
• Small mistakes in the model, like a missing slab edge or the wrong bedroom count, can change the result, so check the numbers against your plans.