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|