Does a JADU inside my existing house need a Title 24 report and MEP plans?

Usually yes, but with a smaller scope than a garage conversion. When a JADU is carved out of rooms that are already heated, the 2025 Energy Code treats it as an alteration, so Title 24 compliance covers only the components you add or change, such as a new water heater, heat pump, lighting, or windows. Requirements vary by city, but expect the building department to want the new kitchen, any bathroom, and related electrical and ventilation work shown on plans.

How the Energy Code classifies a JADU

• Inside existing conditioned space: the CEC's 2025 ADU FAQs and compliance manual say converting existing conditioned space into an ADU or JADU is an alteration; requirements are triggered only by altered components.
• In an attached garage or other unconditioned space: that is newly conditioned space, which follows the addition rules in Section 150.2(a).
• Built with a new home: a JADU created as part of a new house is part of new construction.

Ventilation

Under Section 150.2(a)1C, a JADU that is an addition to an existing building is exempt from the whole-dwelling ventilation airflow requirement, though kitchen and bathroom exhaust still apply. For a JADU created inside existing space, the CEC says California Mechanical Code requirements may apply, so ask your building department what it expects for the altered rooms.

What state law says about JADU systems

• Efficiency kitchen: HCD's handbook says a city cannot require specific counter or cabinet sizes, specified electrical or gas connections, or appliance types beyond a cooking facility with appliances, a food preparation counter, and reasonable storage. It specifically notes that 220-volt circuits are not required.
• Bathroom: a JADU may have its own bathroom or share the house's. Sharing requires an interior entry to the main living area and, since 2026, owner-occupancy.
• Utilities: a JADU created within the house cannot be required to have a new or separate utility connection unless it is built along with a new single-family home.
• Sprinklers: not required unless your house itself is required to have them.

What it means for your MEP plans

• Electrical: new kitchen receptacle and appliance circuits built to the electrical code (220 volts is optional), new lighting that meets the Energy Code's lighting requirements for alterations, and a check of your panel's capacity.
• Plumbing: a kitchen sink connection, plus fixtures, drains, and venting if you add a bathroom.
• Mechanical: kitchen and bath exhaust, and a heating plan for the space. Confirm early whether the JADU can stay on the house's ducted system or needs its own ductless unit, because the Mechanical Code limits return air between dwelling units.
• Title 24: compliance documents for the altered components, matching your MEP sheets exactly.

If the JADU goes into the attached garage instead, the scope grows to a full addition. Learn more on the California ADU requirements guide, the ADU Title 24 guide, and Title 24 reports.

Sources: energy.ca.gov, energy.ca.gov, energy.ca.gov, hcd.ca.gov.