ADU and JADU

An accessory dwelling unit can be new construction, an addition or an alteration, and that classification drives everything else. These pages start with the unit type, then work through solar, heating and cooling, verification, water heating and the building envelope.

In this section

• Checklists by ADU type (9)
• How the code classifies your ADU (12)
• Solar and battery (7)
• Heat pumps and mini-splits (5)
• Testing and ventilation (10)
• Water heaters and gas appliances (7)
• Windows, insulation and roofs (10)

Checklists by ADU type

What to prepare and what will be checked for a new detached unit, an attached unit, a garage conversion and a junior ADU.

1. Detached ADU Title 24 Report
2. Attached ADU Title 24 Report
3. Title 24 for an ADU Above a Garage
4. Does a JADU Need a Title 24 Report?
5. What Plans Are Needed for an ADU Title 24 Report?
6. New Detached ADU Title 24 Checklist
7. Attached ADU Title 24 Checklist
8. Garage Conversion ADU Title 24 Checklist
9. Junior ADU (JADU) Title 24 Checklist

How the code classifies your ADU

Addition, alteration or new construction: how the classification is decided and what it changes for two-story, prefab and garage-adjacent units.

1. Do ADUs Need Title 24 in California?
2. Does a Garage Conversion ADU Need Title 24?
3. California ADU Rules and Title 24
4. Does a Prefab ADU Need Title 24?
5. Do Pre-Approved ADU Plans Come With Title 24?
6. Title 24 for an ADU on a Multifamily Property
7. ADU Addition vs New Construction: Which Title 24 Rules Apply?
8. ADU Alteration vs Addition: Which Title 24 Rules Apply?
9. ADU Over a Garage: Floor Insulation and Title 24
10. Two-Story ADU Title 24 Requirements
11. ADU Attached to a Garage: How Title 24 Classifies the Project
12. Prefab and Factory-Built ADU Title 24 Requirements

Solar and battery

When a new ADU needs its own solar, when it can share the main house system, and what battery readiness means.

1. Does an ADU Need Solar Under Title 24?
2. When Is a New Home Exempt From the Title 24 Solar Requirement?
3. JA12 Battery Storage Requirements
4. ADU Solar Exceptions and Exemptions Under the 2025 Energy Code
5. Can New ADU Solar Panels Be Added to the Main House System?
6. Can Existing Solar Panels Count for a New ADU?
7. ADU Battery-Ready Requirements Under the 2025 Energy Code

Heat pumps and mini-splits

Heat pump rules for 2026 permits and how ducted and ductless systems differ for an ADU.

1. Title 24 Heat Pump Requirements for Homes
2. Can You Install Electric Baseboard or Wall Heaters Under Title 24?
3. ADU Heat Pump Requirements in California for 2026 Permits
4. Can an ADU Use a Mini-Split Heat Pump?
5. Ducted vs Ductless Mini-Split for an ADU: Title 24 Differences

Testing and ventilation

Which field tests an ADU can expect: refrigerant charge, duct leakage, airflow, ventilation, range hood and filters.

1. Does an ADU Need HERS Registration?
2. What Is the CF1R for an ADU?
3. Whole-House Ventilation Requirements
4. ADU Refrigerant Charge Verification: When Is It Required?
5. ADU Duct Leakage Testing: When Is It Required?
6. ADU Airflow Verification: When Is It Required?
7. ADU Whole-House Ventilation Requirements
8. ADU Kitchen Range Hood ECC Verification
9. ADU Bathroom Exhaust Fan Requirements
10. ADU MERV 13 Filter Requirements

Water heaters and gas appliances

Heat pump water heaters, gas appliances in a new unit and electric-ready wiring.

1. Where Can You Install a Heat Pump Water Heater Under Title 24?
2. Title 24 Water Heater Requirements
3. Title 24 Electric-Ready Requirements
4. ADU Heat Pump Water Heater Requirements
5. Can a New ADU Use a Gas Water Heater?
6. Can a New ADU Use a Gas Furnace?
7. ADU Electric-Ready Requirements for Gas Appliances

Windows, insulation and roofs

Window U-factor and SHGC, skylights, wall, attic and slab insulation and cool roofs, by climate zone.

1. Title 24 Insulation Requirements for Homes
2. Do New Windows Need Title 24?
3. Title 24 Skylight Requirements for Homes
4. ADU Window U-Factor Requirements
5. ADU Window SHGC Requirements
6. ADU Skylight Requirements Under Title 24
7. ADU Wall Insulation Requirements
8. ADU Attic and Roof Insulation Requirements
9. ADU Slab Edge and Floor Insulation Requirements
10. ADU Cool Roof Requirements by Climate Zone

For the bigger picture, see everything you need to know about Title 24, the requirements overview and all Title 24 questions.