Does a new front door have to be U-0.20?

In a new home on the prescriptive path, a solid swinging door is held to an area-weighted average of 0.20. A door with 25 percent or more glass is treated as a window instead. A like-for-like replacement in an existing home is not named in Section 150.2(b).

Is a garage door covered by the door U-factor rule?

Section 150.1(c)5 is written for swinging doors between conditioned space and the outdoors or unconditioned space. A roll-up garage door is not a swinging door.

What if my door has no NFRC rating?

It takes a default from Joint Appendix Table JA4.5.1. Swinging-door defaults start at 0.50, well above 0.20, so a door meant to meet 0.20 needs a rated U-factor.

Title 24 Exterior Door Requirements

A solid swinging door between a new home's conditioned space and the outdoors needs a U-factor of 0.20 or lower. A door that is 25 percent or more glass is judged as a window instead. Replacing a door in the same opening is not named in the alterations rules; only adding door area is. Every exterior door still needs its rating label.

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First, which kind of door is it

Section 100.1 treats an operable opening with under 25 percent glass as a door. At 25 percent or more it is a glazed door and must meet the window rules for U-factor and solar heat gain. Most sliding glass doors, French doors and some entry doors fall in that group; see windows and Title 24. In a new home, up to 3 square feet of door glass is exempt from the window U-factor and heat gain limits.

Solid doors in a new home

Section 150.1(c)5 and Table 150.1-A cap the area-weighted average U-factor of swinging doors at 0.20, the same figure in all 16 climate zones. It covers doors to the outdoors and to unconditioned space such as a garage. A swinging door between the garage and the house that must be fire-protected is excepted.

Where the number comes from

Use the NFRC 100 rating on the label. An unrated door takes a default from Joint Appendix Table JA4.5.1, where swinging-door values run from 0.50 for an insulated metal or 1-3/4 inch wood door up to 1.45 for uninsulated single-layer metal, so reaching 0.20 takes a rated door. The temporary label stays on until the building inspector has seen it. Manufactured doors must also leak no more than 0.3 cfm per square foot of door area at 75 pascals.

Replacing or adding a door

Section 150.2(b)1N applies the 0.20 limit to alterations that add exterior door area. A like-for-like replacement is not named. Weatherstripping still matters: the inspector checks it on exterior doors at final, and a field-built door must be caulked and weatherstripped, except unframed glass and fire doors. A glazed door is fenestration, so replacing a sliding or French door follows the replacement-window rules, and a metal frame raises the questions on aluminum windows.

Garage doors and pet doors

The 0.20 rule is written for swinging doors, and a roll-up garage door is not one. Part 6 defines a door to include roll-up doors and pet doors, and a pet door must meet the 0.3 cfm limit when tested to ASTM E283. For a garage under a bedroom, see ADU above a garage.

Not the accessibility rules

Part 6 asks only about heat loss and air leakage. Door width, hardware and thresholds belong to the Building Code, and the Building Standards Commission notes that one- and two-family dwellings are not subject to accessibility requirements unless they are public housing. For the wider picture, read does a remodel need Title 24.

Common Title 24 Questions

Frequently Asked Questions

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