Do I Need Title 24 for a Guest House?
Yes. A new conditioned guest house is a newly constructed building, and whether it has a kitchen decides how it is counted. With permanent provisions for living, sleeping, eating, cooking and sanitation it is a dwelling unit and the solar calculation adds a dwelling-unit term. Without a kitchen the term is zero.
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The test is the kitchen, not the name
Part 6 has no category for a guest house. Section 100.1 defines a dwelling unit as a unit with complete, independent living facilities, including permanent provisions for living, sleeping, eating, cooking and sanitation. The junior ADU definition applies only inside a single-family building, so a detached unit is judged on that dwelling-unit test. Your planning department may use other words; the building department classifies the building.
What the kitchen does to solar
For a 500 square foot detached unit, Equation 150.1-C gives 0.29 to 0.78 kW in any climate zone when no dwelling unit is counted, so Exception 2 (nothing below 1.8 kWdc) applies everywhere. Count one dwelling unit and the result runs from 1.35 to 2.25 kW. It reaches 1.8 in zones 11, 13 and 15 (1.86, 1.96 and 2.25 kW), while in zone 9 it stays at 1.67. The same building can need panels or not on the kitchen alone, unless a small solar access roof area caps it first.
Other rules that follow the dwelling unit
- Section 150.0(o), whole-dwelling ventilation, is addressed to dwelling units.
- The electric-ready rules for a gas water heater, furnace, cooktop or dryer are written for equipment serving individual dwelling units.
- BESS-ready wiring applies to residences with one or two dwelling units on a service above 125 amps.
An existing guest house
If a conditioned guest house already exists and is repurposed as an ADU, the Energy Commission calls it an alteration, because floor area and volume do not increase. If it was built without a permit, the Commission says the building department decides whether it is documented as new construction or an addition. See unpermitted work, and detached ADUs for the full new-building route.
Related questions: pool houses and the accessory structures guide. Our ADU reports start at the ADU price.
Common Title 24 Questions
- What is Title 24?
- Do I need a Title 24 report?
- How much does a Title 24 report cost?
- How long does a Title 24 report take?
- What is included in a Title 24 report?
- What plans do I need to upload?
Frequently Asked Questions
Not in the Energy Code, which has no guest house category. The test is whether the unit has permanent provisions for living, sleeping, eating, cooking and sanitation.
Adding cooking can turn the building into a dwelling unit, which changes how the building is classified. Tell the department before the work, since a change after the permit may need amended documents.
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