What R-Value Does an Oklahoma City Attic Need?

An Oklahoma City attic should end up between R-38 and R-49. Oklahoma County is in climate zone 3, where ENERGY STAR recommends R-49 total for an uninsulated attic, or adding about R-38 when 3 to 4 inches of insulation are already in place.

What R-38 and R-49 Look Like in Inches

• R-19: about 7 to 8 inches of blown fiberglass or 5 to 6 inches of cellulose
• R-30: about 10 to 12 inches of blown fiberglass or 8 to 9 inches of cellulose
• R-38: about 13 to 16 inches of blown fiberglass or 10 to 11 inches of cellulose
• R-49: about 16 to 20 inches of blown fiberglass or 13 to 14 inches of cellulose

Exact depths vary by product, so installers follow the coverage chart on the bag and leave depth rulers in the attic.

Is R-30 Enough?

R-30 is better than what many older Oklahoma City homes have, but it is below current recommendations. If you are already paying for a crew to come out, going to R-49 costs only a little more material and pays back over a long Oklahoma cooling season.

Why R-Value Is Not the Whole Story

Insulation slows heat, but air moving through it carries heat right past it. Gaps at top plates, light fixtures, plumbing stacks and the attic hatch can undercut a thick layer of insulation. Attic air sealing before insulating makes the R-value you pay for perform the way it should.

Ductwork matters too. Most OKC homes run ducts through the attic, and floor insulation does nothing for them. When ducts and an air handler are up there, roof deck spray foam or a radiant barrier can be worth comparing.

How to Check Your Attic

Measure the depth in several spots with a ruler. If you can see the tops of the ceiling joists, you are below R-30. Look for dark, dirty patches on the insulation, a sign of air leaks, and water stains, a sign of roof leaks. Then read is 6 inches of attic insulation enough.

Attic Insulation Elite offers free attic inspections and written quotes seven days a week, 8am to 8pm. Call (405) 400-2050 or request a free quote online.