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The table below shows the calculations used to determine the estimated 'R' values for the four series types of Thermacell wall configurations.
The effective R value of a wall system may be estimated by the sum of the R value of it's component parts.
Some assumptions must be made that will differ from any particular installation so an exact value will only be obtained from measurement of the whole system under the conditions of use.
In the figures shown winter conditions have been assumed (@ 22o inside and 12o outside)
Wall
Components | K
Value | R Value
125mm | R Value
150mm | R Value
166mm | R Value
200mm | R Value
250mm | | Outside air film | | 0.0240 | 0.0240 | 0.0240 | 0.0240 | 0.0240 | | 5mm Cement Render | | 0.0030 | 0.0030 | 0.0030 | 0.0030 | 0.0030 | 75mm Concrete fill
83.5% of cross section | 1.77 | 0.0353 | | | | | 82mm Concrete fill
83.8% of cross section | 1.77 | | 0.0390 | | | | 99mm Concrete fill
84% of cross section | 1.77 | | | 0.0470 | | | 120mm Concrete fill
89% of cross section | 1.77 | | | | 0.0603 | | 180mm Concrete fill
91% of cross section | 1.77 | | | | | 0.0823 | EPS Faces
2x @ 25mm ea. | 0.0350 | 1.428 | | | | | EPS Faces
2x @ 32mm ea. | 0.0350 | | 1.829 | | | | EPS Faces
2x @ 33mm ea. | 0.0350 | | | 1.886 | | | EPS Faces
2x @ 40mm ea. | 0.0350 | | | | 2.286 | | EPS Faces
2x @ 45mm ea. | 0.0350 | | | | | 2.571 | EPS Struts 75mm long
16.5% of cross section | 0.0350 | 0.353 | | | | | EPS Struts 86mm long
16.2% of cross section | 0.0350 | | 0.398 | | | | EPS Struts 99mm long
16% of cross section | 0.0350 | | | 0.452 | | | EPS Struts 120mm long
11% of cross section | 0.0350 | | | | 0.377 | | EPS Struts 160mm long
9% of cross section | 0.0350 | | | | | 0.411 | 50% of 2mm air space
& 10mm Plasterboard | | 0.028 | 0.028 | 0.028 | 0.028 | 0.028 | | Inside Air film | | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | | | | | | | | | | OVERALL R VALUE | | 1.97 | 2.42 | 2.54 | 2.88 | 3.22 |
The following article from Styropor News (R) June 1993 by BASF Australia Ltd.
How effecetive is EPS as a thermal insulation material?
Extremely effective ... essentially because stabilised air is such a good insulator.
The thermal performance of a material is measured in terms of its resistance to the flow of heat. This thermal resistance is expressed in R values; The higher the number, the better the insulation.
The R value of the most commonly used class is 0.57 for every 25mm of thickness. Thus, 44mm of EPS delivers an R value of 1. By comparision, 1240mm of concrete is required to provide the same R value.
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Specifications 
