California Title 24, Part 6 (the Building Energy Efficiency Standards) is the most aggressive state energy code in the U.S., and its 2022 edition — effective 1 January 2023, with a July 2024 Supplement — puts heat recovery at the center of both nonresidential and multifamily compliance. This article distills the recovery provisions that trigger HRV/ERV specification in California.
Nonresidential Exhaust Air Heat Recovery
The 2022 code adds prescriptive requirements for exhaust air heat recovery based on climate zone, percent of outdoor air, and annual operating hours (Tables 140.4-J and 140.4-K). It also adds a dedicated DOAS prescriptive path (§140.4(p)). A key interaction: a cooling system combined with a DOAS that includes exhaust-air heat recovery is exempt from the economizer requirement below 54,000 BTU/h, whereas a standalone unit needs an economizer above 33,000 BTU/h.
| Element | Title 24 2022 provision |
|---|---|
| DOAS exhaust-air heat recovery | Prescriptive design path added (§140.4(p)) |
| Economizer relief | DOAS + recovery allowed < 54,000 BTU/h without economizer |
| Exhaust recovery tables | 140.4-J (by climate zone / % OA), 140.4-K (by operating hours) |
| Filtration | MERV 13 minimum on mechanical ventilation supply (§120.1(c)1) |
Multifamily HRV/ERV Mandate
For balanced-ventilation multifamily dwelling units in Climate Zones 1–2 and 11–16, the code prescribes a heat or energy recovery ventilator with a minimum sensible heat recovery effectiveness of 67% at design conditions. Fan efficacy limits are strict:
- Unitary ERV/HRV: fan efficacy ≤ 0.6 W/cfm (a mandatory 1.0 W/cfm floor applies in all climate zones).
- Central ERV/HRV (multi-unit): ≤ 1.2 W/cfm, and a bypass function is required so intake air can bypass the core like an economizer.
Decarbonization Direction
The 2022 code strengthens the push from gas to heat pumps (§140.4(a)2) and targets net-zero-energy commercial buildings by 2030. Recovery is the demand-reduction step that makes an all-electric, heat-pump strategy affordable. For the cross-jurisdiction picture, see the building code heat recovery mandate comparison, and for the federal floor see ASHRAE 90.1-2022 (50% minimum). California’s 67% sensible floor for multifamily is notably higher than the federal 50% enthalpy floor.
Sizing Note
Specify the core and verify pressure drop inside the AHU selection calculation. Pair a non-rotating membrane core where cross-contamination control matters; otherwise a wheel clears the 67% threshold comfortably — but watch frost, per energy recovery wheel troubleshooting.
Frequently Asked Questions
What does Title 24 2022 require for nonresidential exhaust recovery?
Prescriptive exhaust-air heat recovery based on climate zone, percent outdoor air, and operating hours, plus a dedicated DOAS prescriptive path.
What is the multifamily HRV or ERV mandate?
In climate zones 1 to 2 and 11 to 16, a minimum 67% sensible effectiveness at design conditions, with strict fan-efficacy limits and a required bypass function.
How does recovery interact with the economizer rule?
A DOAS with exhaust-air heat recovery is exempt from the economizer below 54,000 BTU/h, whereas a standalone unit needs one above 33,000 BTU/h.
How does Title 24 compare to federal 90.1?
California's 67% multifamily sensible floor is higher than the federal 50% enthalpy floor, and it pushes decarbonization via heat pumps.