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Installation and Operation Manual - Stratford II
ENGLISH
8.6.5 R Factor
There are two ways to calculate the R-value of the floor protection. First, by adding the R-values of
materials used, or by the conversion if the K factor and thickness of the floor protection are given.
To calculate the total R value from R values of the materials used, simply add the R-values of materials.
If the result is equal to or greater than the R-value requirements, the combination is acceptable.
R-values of some selected materials are shown below :
Table 2 : Thermal Characteristics of Common Floor Protection Materials
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MATERIAL
CONDUCTIVITY (K)
PER INCH
RESISTANCE (R) PER INCH
THICKNESS
Micore® 160
0.39
2.54
Micore® 300
0.49
2.06
Durock®
1.92
0.52
Hardibacker®
1.95
0.51
Hardibacker® 500
2.3
0.44
Wonderboard®
3.23
0.31
Cement mortar
5.00
0.2
Common brick
5.00
0.2
Face brick
9.00
0.11
Marble
14.3 – 20.00
0.07 – 0.05
Ceramic tile
12.5
0.008
Concrete
1.050
0.950
Mineral wool insulation
0.320
3.120
Limestone
6.5
0.153
Ceramic board (Fibremax)
0.450
2.2
Horizontal still air (
⅛
" [3 mm] thick)
0.135
0.920
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Example:
Required floor protection R of 1.00. Proposed materials: four inches of brick and one inch of
Durock® board.
Four inches of brick (R = 4 x 0,2 = 0,8) plus 1 inch of Durock® (R = 1 x 0.52 = 0.52).
0.8 + 0.52 = 1.32.
This R value is larger than the required 1.00 and is therefore acceptable.
In the case of a known K and thickness of alternative materials to be used in combination,
convert all K values to R by dividing the thickness of each material by its K value. Add R values
of the proposed materials as shown in the previous example.
Common brick K value = 5
Thickness = 4"
R value = Thickness/K = 4/5 = 0.8
Durock K value =1.92
Thickness = 1"
R value = Thickness/K = 1/1.92 = 0.52
Total R value = .8 + 0.52 = 1.32
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Information as reported by manufacturers and other resources
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Horizontal still air can’t be «stack» to accumulate R-values; each layer must be separated with another non-combustible material.
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