Ventis Waterloo FP15, Installation And Operation Manual

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FP15 & FP15A Waterloo - Installation and Operation Manual
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6.3.5.6 R Calculations
The use of an R value is convenient when more than one material is going to be used in the hearth
extension to cover the combustible surface. This is because R values are additive, whereas K values are not.
To find the corresponding R factor to use for some selected materials, please see Table 1: Thermal
Characteristics of Common Floor Protection Materials table.
There are two ways to calculate the R factor of the floor protection. First, by adding the R-values of the
proposed materials or if some K and thickness values are given, by converting them to R values.
To calculate the R factor for a composite floor protection made of a combination of alternative materials,
simply add the R-values of those materials. If the result is equal to or larger than the required R value, the
combination is acceptable. For R-values of some selected materials, see Table 1: Thermal Characteristics of
Common Floor Protection Materials.
Example: If the required floor protection R is equal or higher than 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) + 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 the R values of your proposed
materials as shown in the previous example.
In the previous example: Four inches of brick (K = 4/5 = 0.8) + 1 inch of Durock® (R = 1 / 1.92 = 0.52). 0,8 +
0,52 = 1,32.
Table 1: Thermal Characteristics of Common Floor Protection Materials*
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** (1/8") 0.135 0,920**
* Information as reported by manufacturers and other resources.
** For a 1/8" thickness. You cannot «stack» horizontal still air to accumulate R-values; you must separate each layer of horizontal
still air with another non-combustible material.