Attic Insulation R-Value by State: 2026 Reference

How the DOE and IECC set attic R-value targets

The U.S. Department of Energy and the International Energy Conservation Code divide the country into eight climate zones based on heating and cooling loads. Attic R-value recommendations follow those zones — not state borders.

For retrofits, the DOE recommends R-49 to R-60 in most of the country. For code-minimum new construction, the 2021 IECC requires R-49 in Zones 4–8 and R-30 to R-38 in Zones 1–3.

Retrofit attic R-value target by state

Hot / mixed-humid — R-30 to R-49 (existing homes) or R-38 to R-60 (upgrading for energy savings): AL, AR, AZ (southern), FL, GA, HI, LA, MS, NM (southern), OK, SC, TN, TX

Mixed — R-38 to R-60: CA (most), DE, DC, KY, MD, MO, NC, NJ, NV (southern), VA, WV

Cool — R-49 to R-60: AZ (northern), CO, CT, IL, IN, IA, KS, MA, MI (southern), NE, NM (northern), NY (most), OH, OR, PA, RI, UT, WA

Cold — R-49 to R-60 (target the top of the range): ID, ME, MI (northern), MN, MT, ND, NH, NY (northern), SD, VT, WI, WY

Very cold / subarctic — R-60+: AK

If your home was built before 2010 and has not been re-insulated, you are almost certainly below these targets.

Translating R-value to inches by material

Blown cellulose (R-3.7/in): R-38 ≈ 10.5", R-49 ≈ 13.5", R-60 ≈ 16.5"

Blown fiberglass (R-2.5/in): R-38 ≈ 15", R-49 ≈ 20", R-60 ≈ 24"

Fiberglass batts (R-3.2/in): R-38 ≈ 12", R-49 ≈ 15.5"

Closed-cell spray foam (R-6.5/in): R-38 ≈ 6", R-49 ≈ 7.5"

Measure existing depth from the attic floor to the top of the insulation, not to the top of the framing.

Typical upgrade cost (installed, 1,500 sq ft attic)

Air sealing + blown cellulose from R-19 to R-49: $2,000–$4,200

Air sealing + blown fiberglass from R-13 to R-49: $2,200–$4,600

Removal of damaged insulation + full replacement to R-49: $3,500–$7,500

Spray foam at the roof deck (creates a conditioned attic): $6,000–$14,000

Federal 25C tax credit (30% up to $1,200/year) plus state and utility rebates typically cover 30–60% of a code-minimum attic upgrade.

Find your state's insulation contractors

Attic work is climate-specific and code-specific. Use a local contractor who knows your jurisdiction's blower-door and inspection requirements.

Browse the state directory on the locations page to reach an insulation contractor covering your area — every state has a page with contractors, service coverage, and typical scope.