EPS R-Values Expanded Polystyrene (EPS) R-Values Thickness 1.0 Lb. Density 1.5 Lb. Density 2.0 Lb. Density 3″ 12.51 13.65 14.28 4″ 16.68 18.20 19.04 5″ 20.85 22.75 23.80 6″ 25.02 27.30 28.56