Window and Door Header Insulation: R-3, R-5 and the Four QII Header Designs
In new homes and additions over 700 square feet, a single-member header narrower than the wall needs at least R-3 in a 2x4 wall or R-5 in other assemblies. A header as wide as the wall needs nothing extra if the whole wall has at least R-2 continuous foam outside. Conversions of existing space are excused.
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Four header designs that pass
The compliance manual lets the framer choose among these, each filling the wall cavity:
- Two members with insulation between them, such as two 2x nominal pieces in a 2x4 wall.
- Two members narrower than the wall, with insulation on the interior face, such as two 2x pieces in a 2x6 wall.
- One member narrower than the wall, with insulation on the interior face: a 3-1/8-inch header in a 2x4 wall, or a 4x nominal header in a 2x6 wall.
- One member as wide as the wall, such as a 4x in a 2x4 wall or a 6x in a 2x6 wall, with no added insulation if R-2 continuous rigid foam covers the wall exterior.
The two numbers
The appendix sets R-3 for a 2x4 wall or equivalent width and R-5 for every other assembly on single-member headers. The insulation sits between the interior face of the header and the inside surface of the wall finish. For the full-width header, the appendix asks only that the entire wall have at least R-2.
Wood structural panel box headers also work as load-bearing headers if built to California Residential Code Figure R602.7.3 and Table R602.7.3.
Who is excused
Three groups skip header insulation:
- Additions of 700 square feet or less, where the QII requirement does not apply.
- Alterations, where the alteration section lists no QII item.
- Additions that convert existing unconditioned space, for existing headers (Section 150.2(a)1Av).
The manual's garage example shows the limit: in an 800 square foot addition that includes a converted garage, the old garage walls skip the header rule if cladding stays on, but every new or replaced wall meets all of QII. See the garage conversion question.
Timing
Headers vanish behind drywall, so the ECC-Rater sees them at the insulation visit. A performance model can trade QII away. See quality insulation installation, the 700 square foot addition page, the other odd framing spots in QII special situations, and our residential reports.
Common Title 24 Questions
- When is Title 24 required for a home?
- Does a remodel need Title 24?
- Does a room addition need Title 24?
- What plans are needed for a residential Title 24 report?
- How much does a residential Title 24 report cost?
- How long does a residential Title 24 report take?
Frequently Asked Questions
R-5. The appendix sets R-3 for 2x4 framing or equivalent width and R-5 for all other assemblies.
On a full-width header, yes, if the entire wall has at least R-2 continuous rigid insulation on the exterior, as the manual describes.
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