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Title 24 failure on an ADU: causes and fixes

By the HyreADU research desk. Last checked .

The short answer

A Title 24 failure on an ADU means the design or the finished unit does not meet California’s Building Energy Efficiency Standards (Title 24, Part 6). At plan check it is usually missing or wrong compliance forms.

At final, it is usually a failed field verification, such as duct leakage or insulation. A Title 24 consultant and the installer fix each item, then it is retested.

Why it happens

  • Plan check: compliance forms missing, out of date for the code cycle, or not matching the drawings.
  • Equipment: the heating, cooling or water heating installed differs from what was modeled.
  • Field verification: duct leakage, airflow or refrigerant charge fails a HERS test.
  • Insulation or windows installed differently from the plans.
  • Solar or other required measures missing where the standards require them.

What to do this week

  1. Get the failure items in writing from the plan checker, inspector or HERS rater.
  2. Have your Title 24 consultant check whether the model matches what is built.
  3. Fix installation items with the installer: seal ducts, adjust airflow, correct insulation.
  4. Update and resubmit the forms if equipment changed.
  5. Book the retest or reinspection.

Who fixes it

The Title 24 consultant fixes documents and models; the HVAC installer fixes duct and airflow failures; the builder fixes insulation and windows. See Title 24 consultant and our solar requirements research.

What it costs

The lines are rework, retesting and delay. We publish no amounts. The 2025 standards apply to permits under the current code cycle; check which applies to your permit date.

A mistake to avoid

The mistake to avoid is swapping equipment during the build without telling the Title 24 consultant.

A different water heater, heat pump or window can change the energy model, and the forms on file will no longer match what was installed.

Run every equipment change past the consultant before it is ordered, so the paperwork and the building stay in step.

What to do next: check your lot with the ADU feasibility checker, read the questions to ask an ADU builder, then tell us about your project. Matching is not live yet, so we reply with information, not a quote.

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Questions

What is Title 24?

California’s Building Standards Code. Part 6 holds the energy efficiency standards.

What is a HERS test?

A field check by a certified rater of measures such as duct leakage.

Do garage conversions need Title 24 compliance?

Yes. A conversion to living space must meet the energy standards for that use.

Do all ADUs need solar?

The standards set when solar is required; our research page covers the rules.

Sources

HyreADU is a publisher. It does not design, permit or build ADUs, has no partner builders, and gives no legal, tax, lending or engineering advice.

Rules vary by state and city; California rules are labeled as such. Spotted an error? Tell us through our corrections page. Licensed professionals can also contribute as named sources.