Home Improvement: Understanding R-Values

IS YOUR ATTIC SUFFICIENTLY INSULATED?

Insulation is measured in R-values—the ability to withstand heat transfer. In a cold climate, the following R-values are preferable: R-38 in the roof, R-19 in the wall, and R-22 in the floor. In moderate climates, the following values are desirable:
R-26 in the roof, R-19 in the wall, and R-11 in the floor.

R-VALUES OF COMMON INSULATION:

FIBERGLASS

3 1/2 inches R-13
5 1/4 inches R-21
7 1/4 inches R-25
10 inches R-30
12 inches R-38

MOLDED EXPANDED POLYSTYRENE

1 inch R-4
1 1/2 inches R-6
2 inches R-8

EXTRUDED POLYSTYRENE

1 inch R-5
2 inches R-10

POLYURETHANE AND POLYISOCYANURATE

1 inch R-7 to R-8

CELLULOSE

1 inch R-3.4 to R-3.8