Recommended Insulation R-Values by Climate Zone
For an attic with little or no insulation, ENERGY STAR recommends R-30 in climate zone 1, R-49 in zones 2–3 and R-60 in zones 4–8. If you already have 3–4 inches, the targets are R-25, R-38 and R-49.
What is R-value?
R-value measures how well insulation resists heat flow — higher is better. R-values add up: an attic with R-19 already in place needs another R-30 to reach R-49.
Attic recommendations by zone
| Zone | Where (examples) | Uninsulated attic | With 3–4 in existing |
|---|---|---|---|
| 1 | Hawaii, southern Florida, Puerto Rico | R-30 | R-25 |
| 2–3 | Gulf Coast, Southwest, Southeast | R-49 | R-38 |
| 4–8 | Mid-Atlantic, Midwest, Northeast, mountains, Alaska | R-60 | R-49 |
Check ENERGY STAR's zone map for your county — the examples above are broad.
Inches needed for R-49 and R-60
| Material | R per inch (typical) | R-49 | R-60 |
|---|---|---|---|
| Blown fiberglass | R-2.5 | 19.6 in | 24 in |
| Blown cellulose | R-3.5 | 14 in | 17.1 in |
| Fiberglass batts | R-3.2 | 15.3 in | 18.8 in |
| Closed-cell spray foam | R-6.5 | 7.5 in | 9.2 in |
Find the depth and bag count for your attic with the insulation calculator.