Do garage conversions need Title 24 compliance in California?

Yes — garage conversions require Title 24 energy compliance documentation, but under alteration rules rather than new-construction rules. California's 2025 energy code treats a garage conversion as an alteration because it converts existing floor area instead of adding newly conditioned space, so the requirements are real but generally less comprehensive than a new detached ADU.

Why alteration rules are lighter — but still mandatory

A new detached ADU faces the full menu: solar PV for qualifying projects, a heat pump water heater, all-electric-ready provisions, high-efficiency HVAC, and HERS verification of multiple systems. A garage conversion is reviewed against the systems you are actually adding or altering, which typically means:

• New HVAC — a heat pump/mini-split triggers HERS refrigerant charge verification.
• New water heater — must meet efficiency documentation requirements.
• New lighting — must meet Title 24 efficiency standards.
• Building envelope — walls and ceiling generally don't have to meet new-construction insulation minimums unless those assemblies are being altered. In practice, making a garage habitable usually does involve insulating walls and ceilings, which pulls those assemblies into compliance scope.
• Solar PV — typically does not apply to conversions, since they are alterations, not new construction.

The CF1R still has to be registered

Regardless of the lighter scope, a CF1R (Certificate of Compliance) must be prepared with CEC-approved software, registered with an Energy Code Compliance (ECC) Provider, and submitted with the permit application. Building departments require the registered version — a plain PDF is not accepted. Skipping it produces an incomplete notice and delays the whole submittal.

A common, avoidable correction is applying new-construction rules to a conversion (or vice versa). The CF1R must reflect the alteration pathway and the correct climate zone for your parcel address.

The registration and verification chain

The CF1R is only the first of three documents. During construction, installing contractors complete CF2R certificates confirming the work matches the CF1R, and where HERS verification applies — refrigerant charge on the new heat pump, for example — a certified HERS rater completes a CF3R after field testing. The building department won't issue a certificate of occupancy until the required CF3Rs are registered, so line up your HERS rater early rather than at the finish line.

Practical guidance

• Confirm whether your city has adopted an all-electric reach code — many have, which steers HVAC and water heating toward heat pumps.
• Verify your exact climate zone by parcel address; a wrong zone is a frequent rejection cause.
• Have the same team prepare your Title 24 and MEP plans so equipment specs match exactly.

Requirements vary by jurisdiction — confirm with your local building department. We add a registered CF1R to any MEP order for $240, and bundling keeps the energy report and the mechanical plans perfectly consistent. See Title 24 reports or start your order.