Are French doors windows or doors under Title 24?

With 25 percent or more glass they are glazed doors, treated as fenestration. The manual names French doors in that group.

Does a larger French door opening need a Title 24 report?

Extra glass beyond the old opening is added area that must meet the new-home values, with up to 16 square feet exempt from the area limits. The building department decides the paperwork.

French Door Replacement: Title 24 Requirements

French doors are glazed doors in nearly every case, so they follow the window rules: the manual names them as fenestration when glass is 25 percent or more of the door. The deciding questions are whether the opening is larger than the old one and whether true divided lites raise the default U-factor.

Choose your report
Upload your plans
Pay securely
Permit-ready report by email

The 25 percent test, with French doors named

The manual states that every door with a glass area of 25 percent or more of the door area, French doors included, is a fenestration product covered by the NFRC rating program. Door area is defined as the rough opening, so a pair of leaves and their frame are measured together. A door below the line is opaque, and then only its U-factor matters.

Swapping a window for French doors

The manual's own example replaces a 30 square foot window in a zone 12 house with a pair of 40 square foot French doors. The difference, 10 square feet, is added glass. Because added glass of up to 16 square feet is excused from the total-area and west-facing limits by Exception 2 to Section 150.2(b)1A, no area test applies, but every square foot still meets the U-factor and SHGC. (The manual calls this Exception 1, its 2022 numbering.) Area is tallied wall by wall: equal or smaller glass in the same wall is "altered", the excess is "new".

Muntins can raise the default

If the French doors have no NFRC rating, Table 110.6-A applies. For double-pane glazed doors the defaults are 0.77 in a metal frame, 0.59 with a thermal break and 0.53 in a nonmetal frame. Footnote 1 adds 0.05 for true divided lites, and 0.05 for dividers between the panes when the spacer is under 7/16 inch wide, so a nonmetal door with true divided lites defaults to 0.58. A rated door carries its tested figure instead.

Sealing

A manufactured French door must leak no more than 0.3 cfm per square foot of door area at 75 pascals, and its temporary label stays on until inspection.

For the sliding version of the same decision, read sliding glass door replacement. Solid doors are on exterior doors and Title 24, the single-pane remodel is on this remodel page, and our residential reports cover the glazing.

Common Title 24 Questions

Frequently Asked Questions

Explore Windows and Doors

View all Windows and Doors guides → · Windows and Building Envelope · Title 24 guide