Can an ADU Use a Mini-Split Heat Pump?
Yes. The Energy Commission's ADU guidance confirms a mini-split or multi-split heat pump is an accepted system, provided it meets the mandatory equipment rules in Sections 110.2 and 150.0(h). Depending on the project, an ECC-Rater, the field verifier formerly called a HERS rater, tests refrigerant charge, rated heating capacity and other measures.
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Why attached ADUs lean this way
The California Mechanical Code does not allow return air from one dwelling unit to reach another through a shared system. The compliance manual points out that systems without ducts are an option, and Example 9-7 rules out extending an existing furnace with a central return to serve a 600 square foot attached ADU. A ductless system sidesteps the problem.
What the ECC-Rater may check
The Energy Commission lists duct leakage and fan efficacy for ducted systems only. For a mini-split the list may add verified SEER2, HSPF2, rated heating capacity, minimum airflow and refrigerant charge, which is required in every climate zone for heat pumps. Where the standard charge procedure cannot be used, the installer weighs in the charge and the rater verifies it. In an alteration, thermostats on the system must be replaced with setback thermostats. The refrigerant charge page has the procedure and ADU registration explains the paperwork.
Placement and sizing
- The outdoor unit must sit at least 5 feet from the outlet of any dryer vent.
- A liquid line drier is installed if the manufacturer calls for one.
- Heat must be able to hold 68 degrees F three feet above the floor and two feet from exterior walls in habitable rooms, which the load calculation has to show.
- Capacity is selected under ACCA Manual S-2023 from a load calculation.
Mistake to avoid
Assuming ductless means untested. The tests drop away only for ducts. How the ducted and ductless packages differ is on ducted vs ductless, and the rest of the heat pump rules are on ADU heat pump requirements and the residential heat pump page. Reports start on the ADU page.
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 garage conversion ADU need Title 24?
- Does a JADU need a Title 24 report?
Frequently Asked Questions
Yes. The Energy Commission treats mini-split and multi-split systems together, and both must meet Sections 110.2 and 150.0(h) plus the section for the project type.
A garage conversion is an addition. A new system serving it follows the new-home space-conditioning rules, including charge verification in all zones for heat pumps, while extending the existing system does not trigger that.
Explore ADU and JADU
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- Do ADUs Need Title 24 in California?
- Ducted vs Ductless Mini-Split for an ADU: Title 24 Differences
- Garage Conversion ADU Title 24 Checklist
View all ADU and JADU guides → · Permits and Compliance · Title 24 guide