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W415-2007 / D / 04.28.21
EN
10
pre-installation preparation
2.2 hearth extension / floor protection
Hearth extensions / floor protection must be made of non-combustible materials. They must meet the following
specifications:
• Minimum extension to the front of the insert:
- Canada: 18” (45.7cm)
- USA: 16” (40.6cm)
• Minimum 8” (203mm) extension to the sides of the insert
• Minimum 0.5” (13mm) thickness
• Minimum (K*) 0.84 thermal conductivity factor; and
• Minimum (R*) 0.59 resistance value
* See chart below for more information.
THERMAL PROTECTOR:
This appliance must be installed on a non-combustible thermal protector that extends to the front, sides
and back of the appliance as per the minimum requirements below.
The thermal protector must have an overall R-Value of 1.0. For multiple layers, add R-Values for each
layer to determine the overall R-Value.
CONVERTING MATERIAL SPECIFICATIONS TO R OR K VALUES
R = Thickness / K-Value
K = Thickness / R-Value
MINIMUM FLOOR PROTECTION
FRONT (A) SIDES (B) BACK (C) VENT (D)
6” (152mm) 6” (152mm) 8” (203.2mm) 2” (51mm)
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 appliance 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 appliance.
41.3
A
B B
C
D
Floor protection is required for spark and ash shielding, and for limiting fl oor temperatures from the
radiant heat of the appliance.
note:
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