Do I need a cool roof if my attic already has R-38?

For a steep-sloped roof, no. Ceiling insulation of at least R-38 is listed as equivalent to the cool roof product requirement in Exception 1 to Section 150.2(b)1Ii.

Does re-roofing alone trigger R-49 in the attic?

No. The attic rule is triggered by altering the ceiling or installing a new duct system in a vented attic, not by replacing roofing.

Remodel With Roof and Attic Insulation Changes: Title 24 Checklist

Roof and attic work are linked by one exception: ceiling insulation of R-38 or more counts as equivalent to a cool roof product. Re-roofing more than 50 percent of a roof brings the cool roof test; changing the attic ceiling brings R-49, air sealing and recessed can covers. Done together, the attic work can settle the roof test.

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The roof line

Section 150.2(b)1I applies where more than 50 percent of the roof is replaced, including a new layer over the old; the manual's own example says "50 percent or more", so ask the department when a job sits at half. Steep-sloped roofs in zones 4 and 8 to 15 need aged reflectance of 0.20 with emittance 0.75, or SRI 16. Low-sloped roofs in zones 4 and 6 to 15 need 0.63 and 0.75, or SRI 75.

What the attic changes

For steep roofs, Exception 1 treats any of these as equivalent to the product test: ceiling insulation of at least R-38, a radiant barrier, no ducts in the attic in zones 2, 4, 9, 10, 12 and 14, or R-2 continuous insulation above or below the deck. Raising a thin attic to R-49 therefore also satisfies the steep-roof test, with no special roofing product needed.

When attic work triggers its own rules

Section 150.2(b)1J applies when the ceiling over conditioned space is altered, which includes replacing or adding insulation, or when an entirely new duct system goes into a vented attic. Then R-49 applies in zones 1 to 4, 6 and 8 to 16, air sealing in zones 2, 4 and 8 to 16, and covers over recessed cans in zones 1 to 4 and 8 to 16. Existing R-38 exempts all of it; existing R-19 exempts the air sealing, and the can covers in zones 1 to 4 and 8 to 10; asbestos and knob and tube wiring also exempt it. A building official, not an ECC-Rater, checks these items.

Sequence

Put the roof on first, with a rated product and its SRI worksheet where needed, then insulate, so nobody tramples new insulation. On a rafter roof with no attic, work that opens the framing spaces makes the roof altered, and it then takes at least R-19. Record the existing insulation depth and the share of roof replaced before starting.

See re-roofing, cool roof products, insulation requirements and the whole-house checklist.

Common Title 24 Questions

Frequently Asked Questions

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