Closed-cell spray foam: R-value per inch
Short answer
Closed-cell spray foam adds about R-6.5 per inch, so you need roughly 4.6" for R-30 and 7.5" for R-49.
R-value per inch
R-6.5
Best for
Tight spaces, rim joists, crawlspaces (highest R per inch)
Closed-cell spray foam thickness chart
| Target R-value | Thickness needed |
|---|---|
| R-13 | 2.0" |
| R-19 | 2.9" |
| R-30 | 4.6" |
| R-38 | 5.8" |
| R-49 | 7.5" |
| R-60 | 9.2" |
How much for your home?
Calculate closed-cell spray foamOther materials
Frequently asked questions
How many inches of closed-cell spray foam do I need for R-49?
About 7.5" of closed-cell spray foam, since it adds roughly R-6.5 per inch (R-49 ÷ 6.5).
What is the R-value of closed-cell spray foam per inch?
Closed-cell spray foam provides about R-6.5 per inch (a typical value — density and brand vary). So 4.6" gives roughly R-30.
What is closed-cell spray foam best used for?
Tight spaces, rim joists, crawlspaces (highest R per inch). Compare it against other materials for your target R-value in the calculator.