Users might see the "Err" reported in the table of solar gains as below:
Errors like these are not expected usually, but can arise because of missing material construction properties. This issue generally occurs if the model has been opened in an unrelated Workset - i.e. one which does not have the same construction types in it.
Fundamental factors or constants for the fabrics are sometimes not considered and that creates a malfunction in the calculation. See below:
In this example, this results in an invalid fabric gain of "NaN":
To avoid this issue, users should create a new Workset for each project and ensure not to subsequently open the model in different Worksets.
To understand folder structure of Workset and Workspace, refer to this link here
To understand the gain types, please refer to the article here.