Title 24 tools.
Four things we get asked constantly, built so you can answer them yourself in under a minute. No email gate, no account, nothing stored.
Check it yourself, right now
The commonest reason a residential project falls off the prescriptive path. Enter the floor area and your glazing, and see where you land.
Screening tool, not a compliance determination. Prescriptive limits per Table 150.1-A and §150.1(c); additions per §150.2. Over the line means the performance method, which is not the same as failing.
Set by the date the permit application was submitted, not by when the plans were drawn, and not by when construction starts.
Prescriptive quick reference
The residential numbers people ask for most.
| Item | Prescriptive value |
|---|---|
| Window U-factor (max) | 0.30 |
| Window SHGC (max) | 0.23 |
| Total fenestration | 20% of CFA |
| Addition over 700 sf | 175 sf or 20% |
| Addition 400–700 sf | 120 sf or 25% |
| Addition 400 sf or less | 75 sf or 30% |
| Addition west-facing | 70 sf / 60 sf |
Addition allowances are the greater of the square footage or the percentage, and are banded by the size of the addition. Window U-factor and SHGC vary by climate zone; west-facing limits do not apply in Climate Zones 1 and 16. These are the common residential figures — your project's actual targets come out of the model.
Which forms does your project need?
Four questions, and you'll know the compliance path, the exact forms, and whether an ECC/HERS rater has to visit the site.
Find your climate zone
Schematic: nodes are placed for legibility, not survey accuracy. Zone boundaries follow ZIP code lines.
Enter a city or ZIP code, or click any numbered node on the map, and we'll tell you the zone, what drives the design there, and where projects usually lose margin.
Zone assignment is set by the California Energy Commission and follows ZIP code boundaries. A handful of cities straddle two zones. If yours is one of them we will confirm it from the address for free.
About these tools
Is the glazing checker a compliance determination?
No, and it isn't meant to be. It screens your project against the prescriptive fenestration limits, total glazing at 20% of conditioned floor area and the west-facing limit, so you know early whether you're heading for a straightforward run or a fight.
Failing the screen does not mean failing Title 24. It means the prescriptive path is out and you need the performance method, which is what most of our work uses anyway.
Why does west-facing glazing get its own limit?
Because afternoon sun is the worst thermal load a California house takes. The sun is low, it comes in sideways under any overhang you've drawn, and it arrives at the hottest part of the day when the building is already warm.
In the desert zones a west window can cost several times what the same window costs on the north side.
Which code cycle applies to my permit?
The 2025 Energy Code applies to permit applications submitted on or after 1 January 2026. Applications submitted before then stay under the 2022 code. The checker on this page resolves it from your application date.
Tools got you to a question. We can answer it.
Send the plans and we'll tell you where the project actually stands. No charge, before anyone commits to anything.
Or call (909) 914-0305 and you'll get the engineer, not a receptionist.