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SECTION V: FLOOR PROTECTION
Hearth Extension
The firebox on your insert will extend out eight inches (8") from the face of the fireplace, so you will
need at least sixteen inches (16") in front of the door. If you do not have this, it will require you to
place an approved floor protector in front of the stove (such as a hearth extender shield).
Alternate Floor Protection:
An easy means of determining if a proposed alternate floor protector meets requirements is to
follow this procedure:
Convert specification to R-value:
1)
R-value is given – no conversion is needed
i
k-factor is given with a required thickness (T) in inches: R = 1/k x T
ii
C-factor is given: R = 1/C
iii
Determine the R-value of the proposed alternate floor protector:
2)
Use the correct formula given in step 1 (above) to convert values not expressed as "R."
i
For multiple layers, add R-values of each layer to determine overall R-value.
ii
If the overall R-value of the system is greater than the R-value of the specified floor protector,
3)
the alternate is acceptable.
EXAMPLE:
The specified floor protector should be ¾" thick material with a k-factor of 0.84. The proposed
alternate is 4" brick with a C-factor of 1.25 over 1/8" mineral board with a k-factor of 0.29.
Step (a): Use formula above to convert specification to R-value.
R = 1/k x T = 1/0.84 x .75 = 0.893
Step (b): Calculate R of proposed system.
4" brick of C = 1.25, therefore R brick = 1/C =1/1.25 = 0.80
1/8" mineral board of k = 0.29, therefore Rmin.bd. = 1/0.29 x 0.125 = 0.431
Total R = Rbrick + Rmineral board = 0.8 + 0.431 = 1.231
Step (c): Compare proposed system of R of 1.231 to specified R of 0.893.
Since proposed system R is greater than required, the system is acceptable.
Definitions:
Thermal conductance = C
Thermal conductivity = k
Thermal resistance
=
Btu
2
(hr)(ft
)(deg F)
=
(Btu)(inch)
2
(hr)(ft
)(deg F)
2
= R
= (ft
)(hr)(deg F)
Btu
7
=
W
2
(m
)(deg K)
=
W
=
(m)(deg K)
(hr)(ft)(deg F)
2
= (m
)(deg K)
W
Btu
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