Open-cell spray foam: R-value per inch
Short answer
Open-cell spray foam adds about R-3.6 per inch, so you need roughly 8.3" for R-30 and 13.6" for R-49.
R-value per inch
R-3.6
Best for
Walls and ceilings; also air-seals
Open-cell spray foam thickness chart
| Target R-value | Thickness needed |
|---|---|
| R-13 | 3.6" |
| R-19 | 5.3" |
| R-30 | 8.3" |
| R-38 | 10.6" |
| R-49 | 13.6" |
| R-60 | 16.7" |
How much for your home?
Calculate open-cell spray foamOther materials
Frequently asked questions
How many inches of open-cell spray foam do I need for R-49?
About 13.6" of open-cell spray foam, since it adds roughly R-3.6 per inch (R-49 ÷ 3.6).
What is the R-value of open-cell spray foam per inch?
Open-cell spray foam provides about R-3.6 per inch (a typical value — density and brand vary). So 8.3" gives roughly R-30.
What is open-cell spray foam best used for?
Walls and ceilings; also air-seals. Compare it against other materials for your target R-value in the calculator.