The short answer
ENERGY STAR recommends attic insulation of R-30 in the warmest climate zone (1) and R-60 in the cold north for an attic with none, about 8.9 to 17.3 inches of loose-fill cellulose. Floors over a crawlspace or garage need R-13 to R-38, and in Zone 3 and colder, re-sided walls should get R-5 to R-10 of insulating sheathing.
Recommended R-values in every state
ENERGY STAR's recommendation for each state's largest city's climate zone. Mountain and northern parts of a state can be a zone colder: use your ZIP code above.
| Alabama Huntsville | 3A | R-49 | R-38 | R-19 |
|---|---|---|---|---|
| Alaska Anchorage | 7 | R-60 | R-49 | R-38 |
| Arizona Phoenix | 2B | R-49 | R-38 | R-13 |
| Arkansas Little Rock | 3A | R-49 | R-38 | R-19 |
| California Los Angeles | 3B | R-49 | R-38 | R-19 |
| Colorado Denver | 5B | R-60 | R-49 | R-30 |
| Connecticut Bridgeport | 5A | R-60 | R-49 | R-30 |
| Delaware Wilmington | 4A | R-60 | R-49 | R-19 |
| District of Columbia Washington | 4A | R-60 | R-49 | R-19 |
| Florida Jacksonville | 2A | R-49 | R-38 | R-13 |
| Georgia Atlanta | 3A | R-49 | R-38 | R-19 |
| Hawaii Honolulu | 1A | R-30 | R-25 | R-13 |
| Idaho Boise | 5B | R-60 | R-49 | R-30 |
| Illinois Chicago | 5A | R-60 | R-49 | R-30 |
| Indiana Indianapolis | 4A | R-60 | R-49 | R-19 |
| Iowa Des Moines | 5A | R-60 | R-49 | R-30 |
| Kansas Wichita | 4A | R-60 | R-49 | R-19 |
| Kentucky Louisville | 4A | R-60 | R-49 | R-19 |
| Louisiana New Orleans | 2A | R-49 | R-38 | R-13 |
| Maine Portland | 6A | R-60 | R-49 | R-30 |
| Maryland Baltimore | 4A | R-60 | R-49 | R-19 |
| Massachusetts Boston | 5A | R-60 | R-49 | R-30 |
| Michigan Detroit | 5A | R-60 | R-49 | R-30 |
| Minnesota Minneapolis | 6A | R-60 | R-49 | R-30 |
| Mississippi Jackson | 3A | R-49 | R-38 | R-19 |
| Missouri Kansas City | 4A | R-60 | R-49 | R-19 |
| Montana Billings | 6B | R-60 | R-49 | R-30 |
| Nebraska Omaha | 5A | R-60 | R-49 | R-30 |
| Nevada Las Vegas | 3B | R-49 | R-38 | R-19 |
| New Hampshire Manchester | 5A | R-60 | R-49 | R-30 |
| New Jersey Newark | 4A | R-60 | R-49 | R-19 |
| New Mexico Albuquerque | 4B | R-60 | R-49 | R-19 |
| New York New York | 4A | R-60 | R-49 | R-19 |
| North Carolina Charlotte | 3A | R-49 | R-38 | R-19 |
| North Dakota Fargo | 6A | R-60 | R-49 | R-30 |
| Ohio Columbus | 4A | R-60 | R-49 | R-19 |
| Oklahoma Oklahoma City | 3A | R-49 | R-38 | R-19 |
| Oregon Portland | 4C | R-60 | R-49 | R-30 |
| Pennsylvania Philadelphia | 4A | R-60 | R-49 | R-19 |
| Rhode Island Providence | 5A | R-60 | R-49 | R-30 |
| South Carolina Charleston | 3A | R-49 | R-38 | R-19 |
| South Dakota Sioux Falls | 6A | R-60 | R-49 | R-30 |
| Tennessee Nashville | 3A | R-49 | R-38 | R-19 |
| Texas Houston | 2A | R-49 | R-38 | R-13 |
| Utah Salt Lake City | 5B | R-60 | R-49 | R-30 |
| Vermont Burlington | 6A | R-60 | R-49 | R-30 |
| Virginia Virginia Beach | 3A | R-49 | R-38 | R-19 |
| Washington Seattle | 4C | R-60 | R-49 | R-30 |
| West Virginia Charleston | 4A | R-60 | R-49 | R-19 |
| Wisconsin Milwaukee | 5A | R-60 | R-49 | R-30 |
| Wyoming Cheyenne | 5B | R-60 | R-49 | R-30 |
How it works
The formula
We find your county's IECC climate zone from your ZIP code and look up ENERGY STAR's recommended R-values for existing homes in that zone.
| Zone | Attic, none now | Add over 3–4 in | Floor |
|---|---|---|---|
| Zone 1 | R-30 | R-25 | R-13 |
| Zone 2 | R-49 | R-38 | R-13 |
| Zone 3 | R-49 | R-38 | R-19 |
| Zone 4 (A or B) | R-60 | R-49 | R-19 |
| Zones 4C, 5 and 6 | R-60 | R-49 | R-30 |
| Zones 7 and 8 | R-60 | R-49 | R-38 |
Assumptions
- R-values from ENERGY STAR's "Recommended Home Insulation R-Values", which is based on the 2021 International Energy Conservation Code (Table R402.1.3) and applies to existing wood-framed homes.
- Climate zones are the IECC zones for your county (U.S. Department of Energy county list).
- Inches are the minimum initial installed thickness of loose-fill cellulose, from GreenFiber's SANCTUARY attic chart; it settles a little over time. Fiberglass batts and blown fiberglass need different depths; the bag or batt label lists them.
Example: a house in climate zone 5
- Attic with no insulation: R-60, about 17.3 in of loose-fill cellulose; with 3 to 4 in already, add R-49 (about 14.3 in) on top
- Floor over a crawlspace: R-30
- Re-siding: add R-5 to R-10 of insulating sheathing; basement walls R-15 sheathing or R-19 batts
Too big or too small
- Seal before you insulate. Air leaks around lights, pipes, wires and the attic hatch bypass insulation; seal them first.
- Keep soffit vents open with baffles, so the attic can breathe.
- Keep clear of hot things: recessed lights not rated for contact, chimneys and flues need clearance.
- Moisture first in basements and crawlspaces: fix water problems before insulating walls.
Questions people ask
What R-value insulation do I need in my attic?
It depends on your climate zone. ENERGY STAR recommends R-30 for an uninsulated attic in the warmest zone and R-60 in the cold north, which is about 8.9 to 17.3 inches of loose-fill cellulose. If the attic already has 3 to 4 inches, add R-25 to R-49 on top of it. Enter your ZIP code above for your zone.
How many inches of insulation is R-60?
About 17.3 inches of loose-fill cellulose (GreenFiber's chart), and about 14.3 inches for R-49 and 11.2 for R-38. Blown fiberglass takes more depth for the same R-value; check the chart on the bag.
What R-value for walls?
For existing frame walls, ENERGY STAR suggests filling empty cavities, which you can blow in through small holes, and in Zone 3 and colder adding R-5 to R-10 of rigid insulating sheathing when the siding is replaced. A 2×4 wall holds about R-13 to R-15; a 2×6 wall R-19 to R-21.
What R-value for floors over a crawlspace or garage?
ENERGY STAR recommends R-13 in the warmest zones, R-19 in Zones 3 and 4, R-30 in Zones 4C, 5 and 6, and R-38 in Zones 7 and 8, for floors over unheated spaces.
Is more insulation always better?
Each extra inch saves less than the one before, so the recommended levels are where the savings still pay for the insulation. Air sealing the attic floor first (around lights, pipes and the hatch) often saves as much as adding insulation, and it should come first.