What R-Value Do I Need? (By Climate & Area)
Updated
Recommended R-values depend on climate and location in the home. Attics need R-38 to R-60, walls R-13 to R-21, and floors R-25 to R-30. Colder climates need the higher end of each range. Check your US climate zone to pick the right target.
R-value measures how well insulation resists heat flow — the higher the number, the better it insulates. But more isn't always necessary; the right R-value depends on where you live and which part of the house you're insulating.
This guide gives recommended R-values by climate zone and area of the home, and explains how to reach them with different insulation types.
Key takeaways
- Attics: R-38 to R-60 (highest priority).
- Walls: R-13 to R-21.
- Floors: R-25 to R-30.
- Colder climate zones need the higher end of each range.
- R-value adds up with thickness — and varies by insulation type.
Skip the math
Get instant numbers with the Insulation Calculator.
Recommended R-values by area
| Area | Warm climate | Cold climate |
|---|---|---|
| Attic | R-38 | R-49 to R-60 |
| Walls | R-13 | R-21 |
| Floors | R-13 | R-30 |
| Basement walls | R-10 | R-19 |
Why the attic comes first
Heat rises, so the attic is where most of it escapes. Bringing the attic up to R-49–R-60 in cold climates delivers the biggest energy savings per dollar — start there before walls or floors.
Hitting your R-value by type
Different insulation reaches a target R-value at different thicknesses. Fiberglass is about R-3.1 per inch, cellulose R-3.5, and closed-cell spray foam R-6.5. To reach R-49 in an attic, you'd need roughly 16 inches of fiberglass or 8 inches of closed-cell foam.
- Fiberglass batt: ~R-3.1 per inch
- Blown-in cellulose: ~R-3.5 per inch
- Closed-cell spray foam: ~R-6.5 per inch
Estimating insulation
Once you know your target R-value and type, estimate the area and cost with our insulation calculator — pick the insulation type and it returns the square footage and an installed-cost range.