Parallel thermal resistance in Openstudio

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Hi everybody,

I would like to know how I can put the roofing material in parallel in OpenStudio for the purpose of calculating the heat gain and heat loss at the roof level. In fact, I have to dimension a building that is a bit special for me because it has a roof made of double PVC and compressed air fabric and a steel frame. I have never done this before and I need your help to know how to do it.

Thanks in advance.