How can I model constructions containing composite layers?
The data input facilities in the software define constructions as a series of homogeneous layers. Constructions containing layers which are composites of two or more materials can be treated by the 'combined method' defined in standard EN ISO 6946. If you are dealing with constructions of this type, our advice is to carry out a U-value by the combined method or one of the other methods allowed by the EN ISO standard, and adjust the homogeneous layer description to match the U-value you obtain.
We are planning to incorporate the combined method, and other more advanced methods, into a future release of the software. However, the combined method presents some difficulties. For example it does not cover constructions containing layers bridged by metal elements (for which it gives an unrealistically high U-value). Also it requires information about the way the constituent elements in different layers overlay one another, which complicates the data description. Thirdly, it does not offer any guidance on incorporating the composite layer characteristics into dynamic conduction calculations. We are working on ways to resolve these issues.
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