Hearth Extension - Marco C 36 HC Installing & Operating Manual

HEARTH EXTENSION:
The hearth extension must be made from a non-combustib$
'
If there is a combustible floor construction in front of the
inorganic material with a thermal conductivity, K of .84
arc
1
fireplace, a hearth extension is required to protect it. The
less. The thermal conductivity, K or thermal resistance, R of
hearth extension, as shown in Figure 36 must be a minimum
materials can usually be obtained from the manufacturer.
of
16"
deep by 46" wide and extend
a
minimum of 8" beyond
The factors are related by the formula K
= f
The thickness
each side of the fireplace opening.
required for various common materials and their factors are
shown in Figure 37.
I
1
FIGURE 36
I
I
Type of
I
K*
I
Minimum Thickness
Insulation Required
I
Johns Manville
CERAFORM 126
.27 .32"
U.S. Gypsum Corp.
MlCORE CV230
.43 .51"
Insulating Board
I
(K-FAC19)
I
7 7
/
.91"
Lydall. Inc.
I
LYTHERM 1401
Standard Oil
DURABOARD LDandHD
.60 .71"
Common Brick
4.92 5.85"
*Units of K are BTU/ln. Hr, Sq. Ft. OF
FIGURE 37
-
COMMON MATERIALS
AND THEIR FACTORS