Polyiso rigid foam board: R-value per inch
Short answer
Polyiso rigid foam board adds about R-6 per inch, so you need roughly 5.0" for R-30 and 8.2" for R-49.
R-value per inch
R-6
Best for
Continuous sheathing (highest-R board)
Polyiso rigid foam board thickness chart
| Target R-value | Thickness needed |
|---|---|
| R-13 | 2.2" |
| R-19 | 3.2" |
| R-30 | 5.0" |
| R-38 | 6.3" |
| R-49 | 8.2" |
| R-60 | 10.0" |
How much for your home?
Calculate polyiso rigid foam boardOther materials
Frequently asked questions
How many inches of polyiso rigid foam board do I need for R-49?
About 8.2" of polyiso rigid foam board, since it adds roughly R-6 per inch (R-49 ÷ 6).
What is the R-value of polyiso rigid foam board per inch?
Polyiso rigid foam board provides about R-6 per inch (a typical value — density and brand vary). So 5.0" gives roughly R-30.
What is polyiso rigid foam board best used for?
Continuous sheathing (highest-R board). Compare it against other materials for your target R-value in the calculator.