HI,I am running a simulation on Bentley Hevacomp V8i.I have created the roof on the Fabric Data Tab. I then click on the MAT Tab. Here i select new project, exposed roof ect. Then under the roof data tab, when I try to add a layer (where i can specify thermal properties of each layer) i am given a "run-time Error '53'" and the porgram closes. Am I taking the right steps etc.?Do you have a tutorial available?Please respond with urgency.Thanks and Kind RegardsJack