# §150.0(g): Door U-factor
What it requires
Every exterior door on a California residence must meet:
- Solid (≤ 25% glazing) doors: U-factor 0.20 maximum (NFRC-labelled assembly value).
- Glazed doors (> 25% glazing): fall under §110.6 fenestration rules instead, and the U-factor / SHGC values from §150.1(c)3 apply.
The line between "door" and "fenestration" is set at exactly 25% glazing area, measured against the rough opening. A French door, a sliding glass door, or any door with a full-light panel always counts as fenestration. A panel door with a single small light usually counts as a door.
§150.0(g) is one of the simpler mandatory measures — there's no climate-zone variation, and U-factor 0.20 is the floor everywhere in California.
When it applies
Every exterior door on every California residential project. New construction, additions on the addition's new doors, and alterations whenever a door is replaced.
How we use it
The Confirm step pulls door types from your plan's door schedule. For each exterior door, we check the glazing percentage:
- Solid door → §150.0(g) applies, U-0.20 floor.
- Glazed door (> 25%) → §110.6 + §150.1(c)3 rules apply, treated as fenestration.
The CF1R lists every exterior door with its NFRC-rated U-factor on the construction summary. The AHJ field inspector verifies the manufacturer label at final.
Common gotchas
- "Mostly solid" doors with a small light panel that look like they're under 25% by eye but actually clear the threshold — measure against the rough opening, not the door slab.
- Garage-to-house doors — they're interior under the house's air barrier (the garage is unconditioned) and §150.0(g) doesn't apply, but a separate fire-rating requirement does.
- Patio sliders priced as "doors" on the door schedule but submitted to §110.6 fenestration by the AHJ inspector at rough-in.