What R-Value Do I Need? Insulation Chart by Zone
Attic R-38 to R-49, walls R-13 to R-21 by climate zone. Depth check table and insulation types.
Quick answer: In most of the US, attic insulation should be R-38 to R-49 and walls R-13 to R-21. Use the insulation calculator for quantities.
R-value by climate zone (US)
| Zone | Attic | Walls | Examples |
|---|---|---|---|
| 1-2 (hot) | R-30 to R-49 | R-13 to R-15 | Florida, Texas coast |
| 3-4 (mixed) | R-38 to R-60 | R-15 to R-21 | Atlanta, KC, SF |
| 5-8 (cold) | R-49 to R-60 | R-21+ | Chicago, Boston, Minneapolis |
What R-value do I already have?
Check your attic insulation depth:
- R-13 batts: about 3.5 inches
- R-19: about 6 inches
- R-30: about 10 inches
- R-38: about 12 inches
- R-49: about 16 inches
Insulation type guide
| Type | R-value per inch | Best for |
|---|---|---|
| Fiberglass batts | ~3.2 | Walls, DIY attics |
| Cellulose (blown) | ~3.7 | Attics, irregular spaces |
| Spray foam | ~6.0 | Highest R, air sealing |
| Rigid foam | ~5.0 | Basements, exterior |
Add insulation or not?
If your attic has less than 10-12 inches of insulation, adding more pays for itself in most climates through lower heating and cooling bills. Never cover exhaust fans or non-IC-rated light fixtures.
FAQ
What R-value is best for an attic?
R-38 to R-49 for most of the US; up to R-60 in far-north zones.
Can I put R-30 over R-19?
Yes — R-values add up. Adding R-30 over R-19 gives R-49 total.
Does the R-value of old insulation degrade?
Fiberglass keeps R-value but can settle or compress over decades — check depth.
Need a different size?
Our free calculators give you the exact answer in seconds.