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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