How to Build an ADU, Day 3: Title 24 Energy Compliance

California's Energy Code: What Every ADU Owner Needs to Know

Title 24 is California's Building Energy Efficiency Standards — and it's one of the most comprehensive energy codes in the world. Every new ADU must comply, and the requirements affect nearly every aspect of your build.

What Title 24 Requires

Insulation

• Walls: R-15 minimum (climate zone dependent)
• Roof/ceiling: R-30 to R-38
• Floors over unconditioned spaces: R-19
• These values may seem like alphabet soup, but higher R-values mean better insulation and lower energy bills

Windows & Doors

• Dual-pane windows with low-E coating are mandatory
• U-factor and SHGC (Solar Heat Gain Coefficient) requirements vary by climate zone
• LA and OC are Climate Zones 8-9, which have specific window performance requirements

HVAC (Heating & Cooling)

• High-efficiency heat pump systems are now preferred (and often required)
• Duct testing is mandatory to prove your system doesn't leak
• Proper system sizing based on Manual J calculations

Water Heating

• Heat pump water heaters are now the standard for new construction
• Solar-ready plumbing may be required depending on your city
• Point-of-use tankless systems can also comply

Lighting

• LED lighting throughout
• Occupancy sensors in bathrooms and laundry areas
• Daylight controls in certain applications

Solar

• New residential construction (including ADUs) generally requires solar photovoltaic systems
• The size depends on your ADU's conditioned floor area
• Battery storage may be required in some jurisdictions

The Title 24 Report

A certified energy consultant produces a Title 24 compliance report (also called a CF1R report). This document:

1. Models your ADU's energy performance using approved software
2. Specifies exactly what materials and systems you need
3. Must be submitted with your building permit application
4. Is verified during construction through field inspections (HERS testing)

How It Affects Your Budget

Title 24 compliance typically requires a property-specific written estimate to an ADU project through:

• Higher-performance windows (a property-specific written estimate more per window than basic)
• Enhanced insulation (a property-specific written estimate more than minimum code)
• Heat pump HVAC and water heater (a property-specific written estimate more than gas)
• Solar panels (a property-specific written estimate, offset by 30% federal tax credit)

The upside? Your ADU will have significantly lower utility bills — often 30–50% less than an older building. Long-term utility savings depend on energy use, local rates, and system performance.

Pro Tips

1. Work with an experienced energy consultant who knows ADU-specific compliance paths
2. Consider going beyond minimum requirements — better insulation and windows pay for themselves in comfort and energy savings
3. Heat pump systems serve double duty (heating AND cooling) and are often the most cost-effective way to comply
4. Solar panels on your ADU can offset the unit's energy use AND contribute to your main home's energy needs

Coming Up Next

Day 4: City Submittal & Plan Check — how to navigate the permitting process, what plan checkers look for, and how to avoid costly corrections.

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Vision ADU handles all Title 24 compliance as part of our design-build service. Get a free estimate and we'll include energy modeling in your proposal.

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• How to Build an ADU, Day 8: Electrical
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