Heatilator • EL36/EL42 • 4044-132 Rev P • 02/07
26
8
8
Finishing
Fire Risk
• Metal hearth strips MUST be installed.
Sparks or embers may ignite
fl
ooring.
WARNING
Hearth Extension Insulation Alternatives, R Value = 1.16
Material
k per inch
thick
r per inch
thick
Minimum
thickness
required
Hearth & Home HX3, HX4
0.43
2.33
1/2 in.
USG Micore 300™
0.46
2.18
1/2 in.
USG Durock™ Cement Board
1.92
0.52
2-1/4 in.
Cement Mortar
5.0
0.20
5-7/8 in.
Common Brick
5.0
0.20
5-7/8 in.
Ceramic Tile
12.50
0.08
14-5/8 in.
Armstrong™ Privacy Guard Plus
0.46
2.18
1/2 in.
Marble
14.3-20.0
0.07-0.05
16-5/8 in.-23-3/8 in.
A. Hearth Extension
A hearth extension must be installed with all
fi
replaces to
protect the combustible
fl
oor in front of the
fi
replace from
both radiant heat and sparks.
Table 1
To determine the required thickness for an alternate mate-
rial, and if you know the R values of the materials you want
to use, add the values until the result is equal to or larger
than the R value required by your installation.
Example: Required R Value = 1.16
1 in. cement board (R = .52) + 3 in. brick (R = .60) + 1 in.
marble (R = .07).
Total R value = 1.19
K alt.
.43
x .5 = thickness of alternate material
Example: K of Brick = 5
5
.43
x .5 = 5.81 in. of
This
fi
replace has been tested and approved for use with a
hearth extension insulated to a minimum R value of 1.16.
To substitute materials for the factory-available hearth exten-
sions and calculate insulation alternatives as per Table 8.1
and the following formulas:
• K = Thermal conductivity per inch thickness. The lower
the K value, the less heat a material will transfer,.
• R = Thermal resistance per inch thickness. The higher the
R value, the less heat a material will transfer.
• To calculate the required thickness for the alternate
material, you need to know the K value for that material
and use the following formula:
A
B
C
Figure 1 Hearth Extension Dimensions
Model #
A
B
C
EL36
in.
52
16
8
mm
1321
406
203
EL42
in.
66
20
12
mm
1676
508
305
