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W415-1087 / A / 06.06.13
10
EN
99.2C
CONVERTING MATERIAL SPECIFICATIONS TO R OR K VALUES
R = Thickness / K-Value
K = Thickness / R-Value
COMMON K and R VALUES CHART
MATERIAL K-VALUE R-VALUE
Per inch Per inch
Micore 300 0.43 2.33
Wonderboard (cement board) 1.92 0.52
Common Brick 5.00 0.20
Cement Mortar 5.00 0.20
Ceramic Tile 12.50 0.08
Marble 11.00 0.09
Air Space (ventilated) 0.70 1.43
Sand and Gravel 1.70 0.59
Drywall (gypsum) 1.00 1.00
Rockwool or Fiberglass Batts 0.30 3.33
With K values, the lower value is a better insulator. With R values, the higher number is better.
K-Value Example:
A wood stove may call for thermal protection which has a K factor of 1 or less. A product
such as Micore 300 Board from USG has a K-Value of approximately .43 per inch.
Therefore, a 1/2” (12.7mm) thickness of this board would have a K-Value of .86, which
meets the requirement of our example stove.
R-Value Example:
This fi replace calls for thermal protection with an R-Value of 0.59. This same board
above is rated as having an R-Value of 2.33 for a 1” (25.4mm) thickness. Therefore,
1/2” (12.7mm) of the Micore 300 Board would have a R-value of 1.165, which meets
the specifi cations for this fi replace.
3.2 HEARTH EXTENSION/FLOOR PROTECTION
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