Physics > Insulation (R Values)
The term 'R-Value' is used mainly in the building trades to describe the insulating properties of certain materials. The higher the 'R' value, the greater its insulating properties.
A table containing 'R' values of specific materials is included below.
Material |
R value (ft^2 °F h/Btu) |
Hardwood siding (1 in. thick) |
0.91 |
Wood shingles (lapped) |
0.87 |
Brick (4 in. thick) |
4.00 |
Concrete block (filled cores) |
1.93 |
Fiberglass batting (3.5 in. thick) |
10.90 |
Fiberglass batting (6 in. thick) |
18.80 |
Fiberglass board (1 in. thick) |
4.35 |
Cellulose fibre (1 in. thick) |
3.70 |
Flat glass (0.125 in thick) |
0.89 |
Insulating glass (0.25 in space) |
1.54 |
Air space (3.5 in. thick) |
1.01 |
Free stagnant air layer |
0.17 |
Drywall (0.5 in. thick) |
0.45 |
Sheathing (0.5 in. thick) |
1.32 |