Typical R-values for common insulation materials are summarized in this table, which also identifies the vapor retarder classification for each insulation.
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Table 1. Typical R-Values and Vapor Retarder Classifications for Common Insulation Materials. |
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Insulation Type |
R-Value per inch (ft2h°/Btu-in) |
Air Barrier? |
Vapor Retarder Classification Class I: ≤ 0.1 perm Class II: > 0.1 perm to < 1.0 perm Class III: > 1.0 perm to < 10 perm |
|
Fiberglass Batt or Board |
2.5-4 |
No |
Depends on facing |
|
Mineral Wool Rigid Board (Mineral Fiber) |
3-4 |
No |
Depends on facing |
|
Expanded Polystyrene (EPS) |
3.8-4.4 |
Yes |
Typically Class III (2.6 perm/inch) |
|
Extruded Polystyrene (XPS) |
5 |
Yes |
Typically Class II (1.2 perm/inch) |
|
Polyisocyanurate (Polyiso) |
Approx. 6 |
Yes |
Depends on facing, typically Class I |
|
Polyurethane Spray Foam (high-density) |
Approx. 6 |
Yes |
Typically Class II (1 perm/inch) |