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5100-I ACT WOOD INSERT
Page 10
September 1, 2008
R
438-0380D
Thermal protection must be 1/2 inch (13mm) minimum
thickness (“k” value = 0.8) or equivalent material.
All oor protection must be non-combustible (i.e., metals,
brick, stone, mineral ber boards, etc.). Any organic materi-
als (i.e., plastics, wood paper products, etc.) are combustible
and must not be used. The oor protection specied includes
some form of thermal designation such as R-value (thermal
resistance) or k-factor (thermal conductivity).
A. Floor Protection USA & Canada
4
Installation Considerations
C. Hearth Extension
If the hearth extension is lower than the replace opening,
the portion of the insert extending onto the hearth must be
supported. Manufacturer designed adjustable support kit
can be ordered from your dealer. (See page 22).
B.
Calculating Alternate Floor Protection Material
Thermal Conductivity: k value
The k value indicates the amount of heat (in BTU’s) that will ow
in 1 hour through 1 square foot of a uniform material 1 inch thick
for each degree (F) of temperature difference from one side of
the material to the other. The LOWER the k factor means less
heat is being conducted through the non-combustible material to
the combustible material beneath it. The k value of a material
must be equal or smaller then the required k value to be accept-
able.
(BTU) (inch)
(foot
2
(hour) (
o
F)
Thermal Resistance: R value
The R value is a measure of a material’s resisteance to heat
transfer. R value is convenient when more than one material is
used since you can add the R values together, whereas you can
not do this for k value. The HIGHER the R factor means less
heat is being conducted through the non-combustible material to
the combustible material beneath it. The R value of a material
must be equal or larger then the required R value to be accept-
able.
Converting k to R:
Divide 1 by k and multiply the results times the thickness in inch-
es of the material.
R = 1/k x inches of thickness
Converting R to k:
Divide the inches of thickness by R.
k = inches of thickness/R
Calculatons:
Example: Floor protection requires k value of 0.8 and / inch
thick.
Alternative material has a k value of 0.6 and is / inch thick.
Divide 0.6 by .5 = k value of 0.80. This k value is smaller than
0.84 and therefore is acceptable.
Table 4.1
Material
k per
inch
thick
R per
inch
thick
Minimum
thickness
required
Hearth & Home HX, HX
0.43 2.33 1/2 in.
USG Micore 00™
0.46 2.18 1/2 in.
USG Durock™ Cement Board 1.92 0.52 2-1/4 in.
Cement Mortar
5.0 0.20 5-7/8 in.
Common Brick 5.0 0.20 5-7/8 in.
Ceramic Tile
12.50 0.08 14-5/8 in.
Marble
14.3-
20.0
0.07-
0.05
16-5/8 in.
- 23-3/8 in.
Hearth Extension Insulation Alternatives, R Value = 1.16