R Value Calculations - England's Stove Works 17‐VL Installation & Operation Manual

R Value Calculation
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
i
"R."
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
3)
protector, 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 = R
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
Thermal conductivity
Thermal resistance
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FLOOR PROTECTION
+ R
brick mineral board
= C = _____Btu____
(hr)(ft
= k = __(Btu)(inch)__
(hr)(ft
= R = (ft
Btu
= 0.8 + 0.431 = 1.231
= ____W____
2
)(deg F) (m
= ___W____ = ____Btu____
2
)(deg F) (m)(deg K) (hr)(ft)(deg F)
2
)(hr)(deg F) = (m
2
)(deg K)
2
)(deg K)
W