Finishing; Hearth Extension - Heat & Glo Montana-36 Owner's Manual

8 8

Finishing

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. See Figures 8.1 -8.3.
High temperature
(300°F min.) continuous,
non-combustible sealant
HX3 or HX4
Hearth Ext
Tile, stone or other
or equivalent
non-combustible material
insulation
(see Table below)
Floor constructed of wood or
other combustible material
Figure 8.1 Hearth Extension Construction
The hearth extension should slope away from the front of the
fi replace and chase at 1/8 in. to 1/4 in. per foot. Spark strips
must be used on top of any combustible hearth materials
used for moisture management.
This fi replace has been tested and approved for use with a
hearth extension insulated to a minimum R value of 1.03.
To substitute materials for the factory-available hearth ex-
tensions, see Figure 8.3 and calculate insulation alterna-
tives as per Table 8.1 and the following formulas:
• Thermal conductivity per inch thickness = k
• k = (BTU)(inch) / (foot
• Required thickness = Rk
• Thermal resistance per inch thickness = r
• r = (foot 2 )(hour)(°F) / (BTU)(inch)
• Required thickness = R / rB.
Table 8.1
Hearth Extension Insulation Alternatives-Total minimum R Value must equal 1.03
Material
Hearth & Home HX3, HX4 (Micore 300™)
USG Micore 160™
USG Durock™ Cement Board
Cement Mortor
Common Brick
Ceramic Tile
Armstrong™ Privacy Guard Plus
Marble
24 Heat & Glo LifeStyles Collection • Montana US-CAN • 4039-156 Rev C • 11/07
Protective
Metal Hearth
Strip
2 in. (51 mm)
required
2 )(hour)(°F)
k per inch r per inch
thick thick
0.49 2.06
0.39 2.54
1.92 0.52
5.0 0.20
5.0 0.20
12.50 0.08
0.46 2.18
14.3-20.0 0.07-0.05
Fire Risk
•
Sparks or embers may ignite fl ooring.
Metal strips are placed 2 in. (51 mm) under the front
of the fireplace and must extend beyond the front
and sides of fireplace opening by 2 in. (51 mm).
Figure 8.2 Positioning the Protective Metal Hearth Strips
Fire Risk
•
High temperatures or hot embers may ignite
concealed combustibles.
Minimum
thickness
required
1/2 in.
1/2 in.
2 in.
CAT. #
5-1/8 in.
HX3
5-1/8 in.
12-1/4 in.
HX4
1/2 in.
14-5/8 in. - 20-3/8 in.
Figure 8.3
WARNING
Metal hearth strips MUST be installed.
1 in. (25 mm) overlap
WARNING
Hearth extensions must be installed
exactly as specifi ed.
A
C
A B
in 52 16
mm 1321 406
in 66 20
mm 1676 508
Hearth Extension Dimensions
B
C
8
203
12
305