Can I use R-19 in a 2x4 wall?

No. It would be compressed, losing R-value. 2x4 walls take R-13 or R-15 batts.

Is R-19 enough for a crawl space floor?

R-19 is the level most commonly specified for raised wood floors in California.

R-19 Fiberglass Insulation

R-19 fiberglass batts are sized for 2×6 walls and are the standard insulation for raised floors over crawl spaces. Shop kraft-faced R-19 from Knauf, CertainTeed and Johns Manville, or have our licensed crew install it.

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Where R-19 Belongs

2x6 exterior walls in additions, ADUs and remodels. About 6¼ inches thick, R-19 fills the cavity.
Raised floors over crawl spaces, common in older LA, Pasadena and Glendale homes. See crawl space insulation.
Walls between the house and an attached garage.

R-19 Isn't for Attics

R-19 is far below what California attics need. For attic floors choose R-30 or R-38.

Installing R-19 Under a Floor

Kraft facing goes up toward the heated floor; hold batts in place with wire supports. Put a vapor barrier on the crawl space ground first.

Want it done for you? See our crawl space insulation installation service.

R-19 Fiberglass Insulation FAQ

Can I use R-19 in a 2x4 wall?: No. It would be compressed, losing R-value. 2x4 walls take R-13 or R-15 batts.
Is R-19 enough for a crawl space floor?: R-19 is the level most commonly specified for raised wood floors in California.