How thick is R-30 fiberglass insulation?

About 10 inches for a standard fiberglass R-30 batt.

Is R-30 or R-38 better for my attic?

R-30 suits mild coastal areas; hotter inland areas benefit from R-38.

R-30 Fiberglass Insulation

R-30 fiberglass batts are the right attic level for California’s mild coastal zone and the standard for floors over garages and unconditioned space. Choose Knauf, CertainTeed or Johns Manville kraft-faced R-30, or have our licensed crew install it for you.

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When R-30 Is the Right Choice

Coastal attics: in climate zone 6 (Santa Monica, the beach cities, much of West LA) Title 24 sets R-30 as the prescriptive ceiling value for new homes.
Floors over garages and bonus rooms over unconditioned space.
2x10 joists, where a roughly 10-inch batt fills the cavity.

When to Go Higher

Inland, from the San Fernando Valley to the Inland Empire and Las Vegas, R-38 is the better target. Tight on space? Rockwool Comfortbatt R-30 reaches R-30 in about 7¼ inches.

Faced Batts: Which Way Up?

The kraft facing always faces the heated space: down on an attic floor, up on a floor over a garage. Never lay faced batts over existing insulation.

Need help? Call 800-778-3765 or see our attic insulation installation service.

R-30 Fiberglass Insulation FAQ

How thick is R-30 fiberglass insulation?: About 10 inches for a standard fiberglass R-30 batt.
Is R-30 or R-38 better for my attic?: R-30 suits mild coastal areas; hotter inland areas benefit from R-38.