Does a Garage Conversion ADU Need Title 24?
Yes. Converting a garage into an ADU turns space that was never heated or cooled into conditioned space, and the Energy Code treats that as an addition — so compliance documentation is required.
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An addition, not a new building
This is the distinction that matters most on a garage conversion, and it works in the owner's favour. Because the garage already exists as a structure, converting it is not newly constructed floor area — it is newly conditioned floor area, which the code handles under its addition provisions. Where the garage is attached, it is an addition sharing a common wall with the house.
The practical consequence is that the solar photovoltaic requirement that applies to newly constructed dwellings does not attach to a conversion. A detached ADU built from scratch on the same lot would face it; the garage conversion does not.
The insulation relief that applies here
Bringing an old garage up to current envelope standards can be awkward, because the walls were never built for it. The code recognises this. Where an existing unconditioned structure is being converted and the exterior siding or cladding is not being removed, an exception to the prescriptive continuous insulation requirement is available for those walls.
That exception is worth knowing before the design is fixed, because the alternative — stripping and re-cladding an elevation to add exterior insulation — is a significant cost that the project may not need to carry.
What still has to be dealt with
Plenty. The floor is usually an uninsulated slab. The roof or ceiling often has no insulation at all. The large door opening becomes wall or glazing and has to be documented as whichever it becomes. Heating and cooling is new, and so is water heating if the unit has its own. Each of those is an input to the report, and together they decide whether the design complies prescriptively or needs the performance path.
Common Title 24 Questions
- Do ADUs need Title 24 in California?
- What plans are needed for an ADU Title 24 report?
- How much does an ADU Title 24 report cost?
- How long does an ADU Title 24 report take?
- Does a JADU need a Title 24 report?
- Does an ADU need solar under Title 24?
Explore ADU and JADU
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- Does a Prefab ADU Need Title 24?
View all ADU and JADU guides → · Permits and Compliance · Title 24 guide