Hearthstone
Clydesdale Fireplace Insert Model 8491
Page 9 of 35
Hearth Requirements & Floor
Protection
Combustible flooring must be protected with a
covering of noncombustible material (slate, marble
tiles, other noncombustible material can be used for
this purpose). The floor protection must extend
beyond the body of the Fireplace Insert at the
minimum as follows and have a minimum “R-Value”
of 1.1.
Figure 3 – Hearth Requirements
Installations in Canada require 18” (45.72 cm) of
floor protection in the front.
Noncombustible Material
Thickness
R-value
Gypsum or plaster board
1
1
/
2
″
0.45
Wallboard, Wonderboard, or
Durock
1
1
/
2
″
0.20
Ceramic board (Fiberfrax or
Micor)
1
1
/
2
″
1.10
Nominal solid clay brick
1
1
″
0.20
Ceramic wall or floor tile
1
1
/
4
″
0.01
Mineral wool insulation
2
1
″
3.12
Cement mortar
2
1
″
0.20
Horizontal still air
2
*
1
/
8
″
0.92
Floor protector’s come with various types of
specifications. To convert a floor protector’s
specification to an R-value, do one of the following:
1. If the R-value is given, use that value - no
conversion is needed.
2. If a K-factor is given with a required thickness (T)
in inches, use this formula: R-value = 1/K x T
3. If a C-factor is given, use the formula: R-value =
1/C
1
According to Intertek Testing Services, Inc.
2
According to ASHRAE Handbook of Fundamentals 1977
To determine the R-value of the proposed alternate
floor protector:
1. Use either the K-factor or the C-factor formula
explained above to convert specifications not
expressed as R-values.
2. For multiple layers of floor protectors, simply add
the R-values of each layer to determine the
overall R-value of the layers.
If the overall R-value of your setup is greater than the
R-value of the specified floor protector, then your
setup is acceptable.
Clearances to NFPA 211 Protected
Surfaces
You can reduce the clearances to combustible
surfaces by using any National Fire Protection
Agency (NFPA) approved wall protection system.
Refer to NFPA 211 for specific and complete details:
National Fire Protection Agency
Battery March Park
Quincy, MA 02269
1-800-344-3555
1-617-770-3000
www.nfpa.org
Clearance to combustibles
figure 4 – clearances to combustibles
A-
Side
wall
=
12”
B- Mantle and top trim
= 27”
*
B- Mantle/ with mantle shield kit
= 11”
*
C- Trim
= 9”
*
Measured from top of sheet metal shroud
