Short answer: typically about R-15.6 to R-17.6 for 4 inches, depending on density (at 75°F).
Typical R-value
| Density | R per inch | 4 in sheet |
|---|---|---|
| 1.0 lb EPS | R-3.9 | about R-15.6 |
| 1.5 lb EPS | R-4.2 | about R-16.8 |
| 2.0 lb EPS | R-4.4 | about R-17.6 |
Typical values at 75°F from the Rapid Insulation EPS data sheet (REV004). Ask us for the full sheet.
Why density matters
Denser EPS has a slightly higher R per inch and is firmer, so pick it where the foam carries load, like slabs. For walls, 1 to 1.5 lb is common.
Need more R?
We cut any thickness, so you can go 5 or 6 inches instead of stacking two sheets.
Want the full data sheet?
Ask and we'll send it. See EPS foam sheets.