Door or glazed door? The 25% line that flips your Title 24 rules

A door with a big window isn't always a door

Here's the thing: under the California Energy Code, whether your opening is a door or a glazed door comes down to one number — how much of it is glass.

The 2025 Energy Code (Part 6) draws the line at 25 percent. Read the two Section 100.1 definitions side by side and the rule is unmistakable:

• DOOR — "an operable opening in the building envelope including swinging and roll-up doors, fire doors, pet doors and access hatches with less than 25 percent glazed area."
• GLAZED DOOR — "an exterior door having a glazed area of 25 percent or greater of the area of the door. Glazed doors shall meet fenestration product requirements."

So the cutoff is exact. At 24 percent glass, it's a door. At 25 percent, it's a glazed door — and a different rulebook applies.

Verified against the live Section 100.1 definitions in the 2025 California Energy Code (Part 6): DOOR is "...with less than 25 percent glazed area"; GLAZED DOOR is "...a glazed area of 25 percent or greater... Glazed doors shall meet fenestration product requirements."

Why the label matters

A plain door is treated as just that — a door. A glazed door is a fenestration product. The Energy Code's own FENESTRATION PRODUCT definition lists "glazed doors" right alongside windows, skylights, and curtain walls.

That's the part contractors and designers miss on patio sliders and half-lite entry doors. Once an opening crosses 25 percent glass, it has to be rated and labeled like a window, not waved through under the looser door treatment.

What do "fenestration product requirements" come down to? Fenestration products carry performance ratings — chiefly U-factor (how much heat the assembly lets through) and SHGC, the Solar Heat Gain Coefficient. The Energy Code names the rating procedures directly: NFRC 100, "Procedure for Determining Fenestration Product U-factors," and NFRC 200, for "Solar Heat Gain Coefficients and Visible Transmittance." A glazed door has to play by those rules. A door under 25 percent glass does not.

What the January 2026 errata changed

This isn't new law — it's a cleanup. The January 1, 2026 errata to the 2025 California Energy Code corrected the GLAZED DOOR definition and moved it under FENESTRATION (buff page 16).

Before, the definition sat off on its own. Now it lives in the FENESTRATION cluster of Section 100.1, right where you'd look for it — and the DOOR definition points straight to it: "When that operable opening has 25 percent or more glazed area it is a glazed door. See Fenestration: Glazed Door."

The threshold didn't move. The 25 percent line has been the rule all along. What changed is that the two definitions now reference each other cleanly, so it's a lot harder to read one without catching the other.

Where it bites at plan check

The stakes are on the paperwork. If you treat a 25-percent-glass patio door as a plain door, the wrong U-factor and SHGC flow onto your compliance forms — values that won't match a product that has to meet fenestration requirements. That's a correction waiting to happen at plan check.

A quick gut-check for the field: eyeball the glass against the whole door. Half-lite and full-lite entry doors, most sliders, and French doors are almost always over 25 percent — treat them as glazed doors. A solid door with a small vision lite usually isn't. When you're near the line, measure the glazed area against the door area and document it, and verify the call with your local jurisdiction before the forms go in. This is code mechanics, not legal advice.

What CrossBeam does with it

CrossBeam tracks the definitions that decide which rulebook an assembly falls under — like the 25 percent line between a door and a glazed door — and flags the moment an errata moves or rewrites one. You get the bright-line threshold and the current code text in plain language, so the right rating lands on the form the first time.