Title 24: What builders need to know

01/29/2026 Sofia Feeney

California’s 2025 Building Energy Efficiency Standards (Title 24, Part 6) are officially adopted and apply to permits submitted on or after January 1, 2026. The residential codes will be in effect for 6 years according to AB130.

If you build homes here, this code cycle is a real shift in project planning & delivery. The biggest change for builders is that the path to compliance now depends on earlier coordination and tighter field verification. The “fix it at final” era is over.

First builders should start with the mindset shift, metrics and expectations changed. The state moved away from the old Energy Design Rating/TDV framing and now uses Long-Term System Cost (LSC), Source Energy and a new Peak Cooling metric for single-family homes.

In plain English, the model is valuing long-term grid cost, fossil energy burden, and peak-hour cooling impacts, not just annual kWh. LSC is a 30-year system-cost view and it weights peak hours more heavily. So designs that look “fine” on paper can fail if they create peak-load problems or rely on fossil-fuel equipment in prescriptive pathways.

Gas-Fired equipment is no longer optional on prescriptive changeouts. For single-family prescriptive compliance, space heating is essentially heat-pump-only. Gas furnaces push you into performance compliance. Same story with water heating, new prescriptive compliance doesn’t allow new gas tankless or gas storage systems. If you want gas, expect performance modeling and likely other offsets.

Ventilation and Indoor Air Quality (IAQ) upgrades are a “must plan for,” not a “nice to have.” The 2025 code strengthens IAQ requirements for HRV/ERV systems to have Fault Indicator Displays (FIDs) and ECC-rater field verification. Expect to see consultants using Whole House Fans where prescriptive packages call for them, high-efficiency heat pumps for HVAC and water Heating due to Peak Cooling metrics. I recommend considering HVAC design early in the permitting process.

HERS is now ECC. You’ll hear a new acronym on jobs, ECC (Energy Code Compliance) Raters, formerly HERS raters. This isn’t cosmetic. The ECC program moved into Title 24 enforcement, added conflict-of-interest rules and tightened the registry process.

Special inspections like QII (Quality Insulation Installation), refrigerant charge verification, ERV/HRV airflow/FID checks and more will be mandatory in more cases. Fail a test and the project gets locked to that rater as “Rater of Record” until it passes. That means delays cost real money.

The builder’s biggest risk is designing blind then paying twice. In my experience we’ve seen $10k–$40k hits in construction costs when projects drift off the approved Title 24 specs, usually discovered late, when the only fix is ripping out equipment or retrofitting distribution systems.

The new code and many authorities having jurisdictions are also asking for load calculations tied to the compliance model. If your HVAC is oversized, mismatched or not room-by-room supported, expect comments during plan review.

The bottom line is you can’t treat Title 24 like paperwork anymore. It’s a design constraint that should be viewed as an opportunity with an integrated design process.

Windows need to be verified with your consultant. One painfully common failure point is windows. The mandatory weighted average U-factor is tighter (0.40 max) and prescriptive U-factors dropped in many climate zones. If you swap glazing packages after the energy model is done, you may blow compliance without realizing it.

A practical rule is to send your energy consultant the actual window quote and specs before you order. Get a quick “yes, this matches the report” in writing. It’s cheap insurance.

Builders should lean on a CABEC Certified Energy Analyst (CEA) and use state resources like EnergyCode ACE and CABEC guidance. But here’s the move that saves jobs. Call your Title 24 consultant at the start of every project and ask for a 10-minute walkthrough of the report. Treat that call like you treat structural engineering kickoff. Working with a CEA early and using the free tools prevents the downstream chaos.

Integrated design is not a buzzword in 2025, it’s how you pass. What early coordination looks like in real life is to get architects, mechanical and energy consultants aligned while plans are still flexible and changes are cheap. Decide early if you’re meeting compliance with ERVs, Whole House Fans, battery/solar strategies, envelope upgrades or performance tradeoffs.

Remember this: 2025 Title 24 needs early CEA help, window/HVAC verification and ECC inspections. Plan ahead to avoid big costly surprises.

By Travis Wade. He is the Founding Principal at Wade Energy, a CABEC Certified Energy Analyst. He can be reached at travis@wadeenergy.com.