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Heat & Glo • Multi-Sided Woodburning Fireplace • 34977 Rev T • 11/07
27
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.
2 in. (51 mm)
required
High temperature
(300°F min.) continuous,
non-combustible sealant
Tile, stone or other
non-combustible material
Floor constructed of wood or
other combustible material
HX3 or HX4
Hearth Ext
or equivalent
insulation
(see Table below)
Fireplace
Protective
Metal Hearth
Strip
Figure 8.1 Hearth Extension Construction
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
2
)(hour)(°F)
• Required thickness = Rk
• Thermal resistance per inch thickness = r
• r = (foot
2
)(hour)(°F) / (BTU)(inch)
• Required thickness = R / rB.
Fire Risk
• Metal hearth strips MUST be installed.
Sparks or embers may ignite fl ooring.
WARNING
Table 8.1
Hearth Extension Insulation Alternatives-Total minimum R Value must equal 1.03
Material
k per inch
thick
r per inch
thick
Minimum
thickness
required
Hearth & Home HX3, HX4 (Micore 300™) 0.49 2.06 1/2 in.
USG Micore 160™ 0.39 2.54 1/2 in.
USG Durock™ Cement Board 1.92 0.52 2 in.
Cement Mortor 5.0 0.20 5-1/8 in.
Common Brick 5.0 0.20 5-1/8 in.
Ceramic Tile 12.50 0.08 12-1/4 in.
Armstrong™ Privacy Guard Plus 0.46 2.18 1/2 in.
Marble 14.3-20.0 0.07-0.05 14-5/8 in. - 20-3/8 in.
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