The table below shows the calculations used to determine the estimated 'R- values’ for the four types of Thermacell wall configurations. The effective R-value of a wall system may be estimated by the sum of the R-value of its 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 @ 22oC inside and 12oC outside.
The following extract is from Styropor News(R), June 1993, by BASF Australia Ltd.Q: How effective is EPS (expanded polystyrene) as a thermal insulation material?
A: 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, 1,240mm of concrete is required to provide the same R value.