PLANNING YOUR INSTALLATION
PAGE 5
FLOOR PROTECTION
This appliance requires a heat resistant non-
combustible approved fireplace hearth or hearth exten-
sion. If a hearth extension is used it must be a 3/8"
(minimum) UL approved hearth pad or equivalent. If the
floor protection is to be stone, tile, brick, etc., it must be
mortared or grouted to form a continuous non-
combustible surface (See
Using Alternate Material As
Floor Protector
on this page).
This protected area must extend a minimum of 16" to
the front of the fuel door opening and 8" beyond both
sides of the fuel door opening
HEARTH PROTECTION
USING ALTERNATE MATERIAL AS A FLOOR PROTEC-
TOR/HEARTH EXTENSION
The alternate material used as a hearth extension must
be constructed of a durable noncombustible material
having an equal or better insulating value (lower k value)
of k = 1.28 BTU/IN FT
2
HR
°
F or a thermal resistance
that equals or exceeds r = 78 HR
°
F FT
2
IN/BTU. With
these values, determine the minimum thick-
ness/material required using the formula and the table
shown here (see chart -
Alternative Floor Protection
Materials
).
Note: Any noncombustible material having a thickness
of 1” whose k value is less than 1.28 or whose r value is
more than .78 is acceptable. If the alternate material
used has a higher k value or lower r value will require a
greater thickness of the material used. In some cases, if
the k value is less or the r value higher, a thinner mate-
rial may be used.
Methods of determining floor protection equivalents
To determine the thickness required for any material
when either the k or r values are known:
T
M
= Thickness of material in inches
K
M
= K value of desired material
T
L
= Minimum listed thickness
Example: Micore CV230 is to be used for the floor pro-
tection. How thick must this material be?
The following
formulas
give the means of determining
minimum thickness required of alternate materials.
Using the
k formula
:
Desired Thickness
k value of desire
Minimum thickness
of the alternate
= material (per inch)
x
of Listed
material
k value of listed
Material
material (per inch)
T
M
(inches) = K
M
x T
L
1.28
T
M
(inches) = 0.43* x 1”
1.28
Answer using k = 0.34 x 1” = 0.34 = 3/8”
3/8” thickness Micore will be required.
Using the
r formula
:
T
M
(inches) = 0.78 x T
L
r
M
T
M
(inches) = 0.78 x 1”
2.33*
Answer using r = 0.34 x 1” = .034 = 3/8”
3/8” thickness Micore will be required.
At times it is important to know what combination of
materials are acceptable for use as floor protection. The
“R values” are used to determine acceptable combina-
tions of materials because “R values” are additive where
r and k values are not.
“R value” = 1 = r x thickness of material used
k
ALTERNATIVE FLOOR PROTECTION MATERIALS
Listed
Values
Min. Thick
Material
k
(per inch)
r
(per inch)
T
L
Millboard
1.28
0.78
1”
Alternative
Values
Min. Thick
Materials
k
(per inch)
r
(per inch)
T
L
Wonderboard
1.92
0.56
1 1/2”
Common brick
5.00
0.20
3 7/8”
Cement mortar
5.00
0.20
3 7/8”
Ceramic tile
12.5
0.08
9 3/4”
Marble
11.0
0.09
8 5/8”
Micore CV230
(U.S. Gypsum)
0.43
2.33
3/8”
Ceraform 126
(Johns-Manville)
0.27
3.70
1/4”
Example: Given that the required “R value” for a suitable
floor protector used must be equal to or greater than:
“R” = r x T
L
= 0.78 x 1” = 0.78.