What are the Title 24 requirements for HVAC in new California ADU construction?

Title 24 — California's Building Energy Efficiency Standards — governs the HVAC system in every new ADU. In short, the 2025 energy code treats heat pumps as the prescriptive baseline for space conditioning, sets minimum equipment efficiencies (SEER2/HSPF2), requires continuous whole-building ventilation per ASHRAE 62.2, and mandates field verification by a HERS rater. The mechanical plans must document all of this and match the Title 24 energy report.

The core Title 24 HVAC requirements

• Heat pump baseline. Under the 2025 code, heat pumps are the prescriptive baseline for new-construction space conditioning. Designing around a mini-split or ducted heat pump is the most direct route to a clean compliance run.
• Minimum equipment efficiency. The selected equipment must meet or exceed current minimum SEER2 (cooling) and HSPF2 (heating) thresholds. Quality mini-splits typically clear these by a wide margin, improving the compliance cushion.
• Whole-building ventilation. Continuous mechanical ventilation meeting ASHRAE 62.2, sized to floor area and bedroom count, is required in every new ADU regardless of size — and is not waivable.
• HERS field verification. A HERS rater field-measures and confirms required items, which commonly include refrigerant charge verification (required in all 16 climate zones), duct leakage for ducted systems, and ventilation airflow.
• Climate-zone-specific design. California's 16 climate zones — determined by parcel address, not ZIP code — set the outdoor design temperatures and efficiency requirements the equipment must satisfy.

How compliance is demonstrated

Title 24 compliance for a new ADU is shown through an energy report (CF1R), and the equipment listed on the mechanical schedule must match the equipment modeled in that report. A mismatch between the drawings and the energy calcs is one of the most common plan-check corrections, so the make, model, and efficiency ratings have to be consistent across both documents.

Climate-zone considerations

Compliance checklist

1. Confirm the climate zone by parcel address.
2. Run a Manual J for peak heating and cooling loads.
3. Select heat-pump equipment meeting current SEER2/HSPF2 minimums.
4. Design ASHRAE 62.2 whole-building ventilation as a separate system.
5. Note HERS verification (refrigerant charge always; duct leakage if ducted; ventilation airflow).
6. Keep the mechanical schedule consistent with the Title 24 energy report.

Code thresholds and verification requirements change between code cycles and vary by jurisdiction — confirm current details with your local building department. Our mechanical plans are prepared to your climate zone, and a bundled Title 24 report (+$240) ties equipment selection to compliance in one coordinated pass. Start your order when ready.