ADU Title 24 Requirements What Your ADU Needs to Pass (2026)

By Roman Leonelli, CEO & Certified HERS / ECC Rater — CHEERS Rater #RCN13486 · Updated June 10, 2026

The short answer

An accessory dwelling unit (ADU) is a complete independent living unit on the same lot as a primary home, and California treats it like any other dwelling under Title 24 — the state's Building Energy Efficiency Standards, found in Title 24, Part 6 of the California Code of Regulations. That means three things for every ADU project: an energy compliance report (the CF1R, or Certificate of Compliance) filed with the building permit, installer certificates (CF2R, Certificate of Installation) during construction, and third-party field verification (CF3R, Certificate of Verification) by a certified HERS rater before the city will sign off the final. Since January 1, 2026, the California Energy Commission (CEC) calls this verification work Energy Code Compliance (ECC) — same tests, new name.

Which requirements hit your project depends on which of the three ADU types you are building:

• Detached new-construction ADU — a new low-rise residential building. The full new-construction package applies, including Quality Insulation Installation (QII) on the prescriptive path.
• Attached ADU — built onto the existing house, treated as an addition under section 150.2 of the Energy Code. Requirements scale with size; the 700-square-foot threshold matters here.
• Conversion ADU — a garage or other existing space converted to living space. Title 24 treats newly conditioned space under the addition rules, but because most conversions are small and reuse the existing shell, they carry the lightest energy-code load of the three.

Step 1 — the CF1R energy report at permit

Before the building department issues your ADU permit, an energy consultant models the design and produces the CF1R. Most ADUs use the performance path: the software trades measures against an energy budget, which is how a design with, say, more west-facing glass can still comply. Whatever the consultant claims on the CF1R — QII, a tested duct system, envelope leakage — becomes a binding checklist for the rest of the project. If a HERS measure is on the CF1R, a certified rater has to verify it in the field.

Published California market pricing for an ADU CF1R runs $250 to $500: Title24Calcs starts ADU reports at $250, Title24EZ publishes $360, and GetTitle24 cites $500 as typical for a new-construction ADU. ERE prepares Title 24 reports as part of its Title 24 report service — call for a fixed quote.

Step 2 — build it and certify the installs

During construction, the installing contractors document their own work on CF2R forms — the HVAC contractor certifies the duct system and equipment, the insulation contractor certifies the insulation, and so on. Under the 2025 Energy Code, heat pump installs added new CF2R items, like a defrost delay timer set to at least 90 minutes and a supplementary-heat lockout above 35°F outdoor temperature, per the CEC's What's New for 2025 single-family fact sheet. The CF2Rs must be registered before the rater can register the verification — an unfinished CF2R is the most common thing holding up an ADU final.

Step 3 — HERS / ECC field verification

A certified HERS / ECC rater — independent of your contractor — tests the finished work and registers the CF3R with an approved data registry. ERE registers with CHEERS, which the CEC approved as an ECC-Provider for the 2025 code on November 12, 2025. Typical HERS measures on an ADU:

• Duct leakage testing — required on new ducted systems; the duct system is pressurized and measured against the leakage target on the CF1R. See duct leakage testing.
• Refrigerant charge verification — under the 2025 code, required for heat pumps in all 16 climate zones (and for air conditioners in zones 2 and 8–15).
• Cooling coil airflow and fan watt draw — confirms the system moves enough air without burning excess fan energy.
• Mechanical ventilation (IAQ) airflow — new dwelling units need whole-dwelling ventilation, and the measured airflow is verified in the field.
• QII — insulation and air-barrier verification before drywall, covered in detail below. See QII verification.

New to HERS testing? Start with What is a HERS test? for the full background.

QII and the 700-square-foot rule

QII (Quality Insulation Installation) is the pre-drywall verification that insulation and the air barrier were installed with no gaps, voids, or compression, per Reference Appendix RA3.5. Per Table 150.1-A of the Energy Code, QII is a prescriptive requirement for new single-family and low-rise multifamily buildings, and for additions larger than 700 square feet, as summarized by Energy Code Ace. Applied to ADUs:

• Detached new-construction ADU: it is a new dwelling, so prescriptive QII applies in all 16 climate zones — regardless of the ADU's size.
• Attached ADU (addition): prescriptive QII applies only when the addition exceeds 700 square feet. At 700 square feet or less, QII is not prescriptively required.
• Conversion ADU: newly conditioned space follows the addition rules, and a typical two-car garage at roughly 400 square feet stays under the 700-square-foot threshold — so prescriptive QII usually does not apply.

One nuance contractors miss: those rules describe the prescriptive path. On the performance path — which most ADUs use — the energy consultant can take QII as a credit to make the model comply even when the prescriptive rule would not demand it. If QII is on your CF1R, it must be verified before drywall, full stop. Scheduling the rater after the walls are closed means opening them back up.

Conversions vs new builds, in practice

A garage conversion reuses the existing roof, slab, and most walls, so Title 24 touches mainly what you change: newly insulated assemblies, the new heating and cooling system, water heating, and ventilation. A new ducted system still gets a duct test; a new heat pump still gets charge verification. A detached new build, by contrast, is modeled and verified as a complete new dwelling — envelope, mechanical, water heating, and QII. That is why two ADUs of identical floor area can carry very different compliance scopes, and why the CF1R — not the square footage — is the document to read before you price the job.

What changed under the 2025 Energy Code

The 2025 Building Energy Efficiency Standards took effect January 1, 2026. The CEC's rule: buildings whose permit applications are applied for on or after January 1, 2026 must comply with the 2025 Energy Code — earlier applications stay on the 2022 code. For ADU projects permitted under the new code:

• Heat pumps are the prescriptive baseline for space heating in all 16 climate zones; installing gas heating instead requires the performance path.
• Heat pump water heaters are effectively the prescriptive baseline too — the gas-tankless option was removed from the prescriptive menu, including for additions.
• More rater verification: refrigerant charge verification for heat pumps in every climate zone, and field verification of HRV/ERV fault indicator displays where those systems are used.
• New name, same tests: "HERS raters" became "ECC raters" under the CEC's Energy Code Compliance program. QII scope and duct-leakage thresholds did not change in the 2025 code.

What ADU Title 24 compliance costs

Most California field-testing companies do not publish prices, so treat these published market ranges as orientation, not a menu: $250–$500 for the ADU CF1R report, $250–$500 for QII verification (it takes multiple site visits), and roughly $150–$450 for a HERS field-test visit depending on how many measures the CF1R lists. The full breakdown with sources is in our guide How much does a HERS test cost? ERE quotes every ADU as a fixed price up front — request a quote or call (310) 807-4800.

Frequently asked

Does my ADU need a Title 24 report?

Yes. Every California ADU that adds or newly conditions living space needs Title 24 energy compliance documents with its building permit, starting with the CF1R (Certificate of Compliance). Detached new-construction ADUs, attached ADUs, and conversions all need one — the difference is which requirements apply, not whether Title 24 applies.

Does a garage conversion ADU need a HERS test?

Usually, yes. If the conversion installs a new ducted heating or cooling system, duct leakage testing applies, and a heat pump triggers refrigerant charge verification under the 2025 Energy Code. A conversion escapes most new-construction envelope measures, but the mechanical work still gets field-verified and registered on a CF3R before the city signs off.

Does my ADU need QII?

A detached new-construction ADU on the prescriptive path needs QII in all 16 climate zones, regardless of size. An attached ADU built as an addition needs it prescriptively only when the addition is over 700 square feet. On the performance path, QII applies whenever your energy consultant takes the credit on the CF1R — and once it is on the CF1R, a certified rater must verify it before drywall.

What is the 700-square-foot QII rule?

Under Table 150.1-A of the Energy Code, additions larger than 700 square feet must meet the same prescriptive QII requirement as new homes, while additions of 700 square feet or less are exempt from prescriptive QII. Title 24 treats newly conditioned space — like a garage conversion — under the addition rules, so a typical two-car garage at roughly 400 square feet stays under the threshold.

How much does Title 24 compliance cost for an ADU?

Published California market data puts an ADU CF1R report at $250–$500, QII verification at $250–$500, and a HERS field-test visit at roughly $150–$450 depending on the measures and number of systems. ERE doesn't price by range — call (310) 807-4800 for a fixed quote on your ADU.

My permit was applied for before January 1, 2026 — which code applies?

The 2022 Energy Code. The California Energy Commission's rule is that buildings whose permit applications are applied for on or after January 1, 2026 must comply with the 2025 Energy Code; earlier applications stay on the 2022 code through construction, including the HERS measures listed on their CF1R.