VGZ-010 / 20120105.0
VG820E HEARTWOOD™
/
Page 19
FLOOR PROTECTOR MATERIAL CALCULATIONS
This stove has been tested for and must be installed on a floor protector with the proper Thermal Resistance
or R-value as stated in the installation instructions on page 6, “Locating Stove” step 1, of this manual. If the
floor protector materials listed in the instructions are not available, materials with an equivalent R-value may be
substituted.
Alternate materials may be rated with C-factor (Thermal Conductance) or k-factor (Thermal Conductivity)
ratings which must be converted to R-value to determine if the alternate material meets the tested requirements.
The following instructions provide the proper information and formulas for conversion to R-value.
To determine if alternate materials are acceptable follow this sequence.
1. Convert material specifications to R-value:
a. R-value given — no conversion necessary
b. k-factor is given with a required thickness (T) in inches:
R = 1/k x T
c. C-factor is given: R = 1/C
2. Determine the R-value of proposed alternate floor protector:
a. Use formulas in step 1 above to calculate R-value of proposed material(s).
b. For multiple layers, add R-values of each layer to determine overall R-value.
3. If the overall R-value of the floor protector system is equal to or greater than the floor protector specifications
given, the alternate is acceptable.
Definitions:
Thermal conductance (C) =
BTU
=
W
(hr)(ft
2
)(°F)
(m
2
)(°K)
Thermal conductivity (k) =
(Btu)(inch)
=
W
=
Btu
(hr)(ft
2
)(°F)
(m)(°K)
(hr)(ft)(°F)
Thermal resistance (R) =
(ft
2
)(hr)(°F)
=
(m
2
)(°K)
Btu
W
Example:
The specs of floor protector material should be 3/4-inch thick material with a k-factor of 0.84.
The proposed alternative material is 4” brick with a C-factor of 1.25 over 1/8-inch mineral board
with a k-factor of 0.29.
Step 1: Convert specs to R-value.
R = 1/k x T = 1/0.84 x 0.75 = 0.893 System must have a R-value of 0.893 = Rspecs
Step 2: Calculate R-value of individual components
4” Brick with C-factor = 1.25. R = 1/C = 1/1.25 = 0.80 = Rbrick
1/8-inch (0.125”) mineral board with k-factor = 0.29. R = 1/0.29 x 0.125 = 0.431 = Rmin.brd.
Step 3: Add R-values of components to get total R-value of system
Rmin.brd = 0.80 + 0.431 = 1.231 = Rsystem
Step 4: Compare Rsystem to Rspecs
Rsystem = 1.231 is larger than Rspecs of 0.893. System R-value exceeds the required
specifications and therefore is an acceptable alternative.
