What are R-Values of Polystyrene and Spray Foams?

Q: What are R-values of polystyrene and spray foams?

R values of polystyrene usually range from 2.3 to 5.0 per inch and are based on its density. Loose-fill polystyrene (tiny pieces of foam or fiber) has a lower R-value, usually 2.3 per inch.  Foam board polystyrene (strong, firm insulation panels) has a higher R-value.

Expanded polystyrene (EPS), for example, has an R-value of 4.0, while extruded polystyrene (XPS) has an R-value of 5.0.

R-values per inch of spray foams are as follows:

Material R-value per inch
polyurethane foam, closed-cell 6.0
polyurethane foam, open-cell 3.6
polyurethane foam, soy-based 3.6
cementitious spray foam 3.9
phenolic spray foam 4.8
polyisocyanurate 5.6 – 8.0



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