EC95
19
INSTRUCTION MANUAL ADDENDUM
This addendum is a supplement to the Installation, Operation, and Maintenance Instruction Manual for this appliance. Do
not neglect to read all instructions thoroughly.
ATTENTION: Installers of Fireplaces, Fireplace Stoves, Room Heaters, and Fireplace Inserts.
SUBJECT: Determining Equivalent Materials for Use as Hearth Extensions and Floor Protectors Over Combustible
Floors.
1. If you are not a qualified installer of the product, we suggest that you consult with a qualified installer or other knowledge-
able person for proper installation of the product. Your local building code official should also be consulted.
2. Refer to the section in the installation instructions on hearth extensions or floor protectors. Use the material specified
in the instructions.
3. If a listed floor protector is specified as an alternate material, consult a local dealer that sells floor protectors which are
listed by a recognized listing agency. If the solid fuel burning appliance requires one or two layers of 3/8 inch thick
millboard, a Listed floor protector may be purchased that is intended for use in place of the required number of layers of
millboard as specified in the instructions.
4. If an equivalent material for use as a hearth extension or floor protector is permitted in the installation instructions and
a K, C, or R factor is specified, be sure (a) that the equivalent material is Listed by a recognized listing agency, (b) that the
K or C factor is equal to or less than the number specified and (c) the thickness of the material is at least equal to the
specified thickness in the installation instructions. The K factor for millboard is equal to 0.84 BTU-inch/(hr.) (°F) (ft
2
), which
can be used to determine equivalency under Item 3 if necessary.
5. For reference, K, C, and R factors are given for building and insulating materials in engineering handbooks such as the
ASHRAE Handbook of Fundamentals and the Standard Handbook for Mechanical Engineers by Baumeister and Marks.
6. K, C, and R factors are explained as follows:
A. The “K” factor represents the thermal conductivity of a material and is the time rate of heat flow through a
homogeneous material under steady-state conditions, through unit area, per unit temperature gradient in the
direction perpendicular to a surface. BTU
or
(Btu)(in.)
_______________
________________________
(hr)(ft
2
)(°F/in.)
(hr)(ft
2
)(°F)
B. The “C” factor represents the thermal conductance of a material at a specific thickness and is applied to a
specific homogenous material used at the stated thicknesses. (Note: The “C” factor is equal to the “K” factor
divided by the thickness of material.)
C. The “R” factor represents the thermal resistance of a material and is defined as the reciprocal of either the
“K” or “C” factor, expressed as “R per inch” (K factor reciprocal) or “R” with reference to a specific material
thickness related to a specific application (C factor reciprocal).
REFERENCES:
1. ASHRAE Handbook, 1981 Fundamentals, published by American Society of Heating, Refrigerating and Air-Conditioning
Engineers, 1981; Chapter 23.
2. Eshbach, O. W., Handbook of Engineering Fundamentals, published by Wiley & Sons, 1936, 1952; Table 2, pp. 13-39
to 13-43.
Note: Use of the K and C constants needs to be carefully considered since the exact number depends on the system of
units involved. The value of the constant is different under different systems of units. K is identified in some tables as “per
inch”; however, from a unit consideration, the “inch” (i.e. thickness) is actually in the numerator, not the denominator, and
to determine the K factor for a specific thickness (i.e., the C factor), it is necessary to divide by the thickness of the
material. Other handbooks or manufacturers’ data cancel the inch of thickness in the numerator with the square feet of
area in the denominator of the K factor, resulting in a variance of 12 in the table of values or in the manufactors’ data. An
example calculation is as follows:
If the floor protector or hearth extension material is specified as one layer of 3/8 inch (0.375 inch) thick millboard with a K
factor of 0.84, the following calculations apply: