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Appendix B
Alternate Floor Protection
All floor protection materials must be non-combustible ie. metal, brick,
stone, mineral fiber boards). Any combustible material may not be used.
The easiest means of determining if a proposed alternate floor material
meets requirements listed in this manual is to follow this procedure.
R-value = thermal resistance
k-value = thermal conductivity
C-value = thermal conductance
1. Convert the specification to R-value;
a. If R-value is given, no conversion is needed.
b. If k-value is given with a required thickness (T) in inches: R=1/k
X T.
c. If C-value is given: R=1/C.
2. Determine the R-value of the proposed alternate floor protector.
a. Use the formula in Step 1 to convert values not expressed as
"R".
b. For multiple layers, add R-values of each layer to determine
overall R-value.
3. If the overall R-value of the system is greater than the R-value of
the specified floor protector, the alternate is acceptable.
139946_18 F 500 V3 Oslo
Example:
The specified floor protector should be 3/4" 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 specifications
to R-value. R=1/k X T= 1/.84 X .75 = .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
R mineral board = 1/.29 X 0.125 = 0.431
Total R = R brick + R mineral board=
0.8 + 0.431=1.231
Step C. Compare proposed system R = 1.231 to specified R of
0.893. Since R is greater than required, the system is acceptable.
Definitions:
Thermal conductance =
C =
Btu
=
(hr)(ft
)(F)
(m
2
Thermal conductivity =
k =
Btu
=
W
(hr)(ft
)(F)
(m
)(K)
2
2
Thermal resistance =
R =
Btu
=
(m
(hr)(ft
)(F)
2
Alcoves require use of a bottom heat shield and hearth protection
having a minimum R-value of 1.6.
May 2022
W
)(K)
2
=
(Btu)
(hr)(ft)(F)
)(K)
=
(Btu)(inch)
2
W
(hr)(ft
)(F)
2
27
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