For example IfcWall objects – IsExternal property is as part of Pset_WallCommon

Is External Indication whether the element is designed for use in the exterior (TRUE) or not (FALSE). If (TRUE) it is an external element and faces the outside of the building.

Note 1: Revit has this built-in parameter only in: Wall, Floors, Stairs, Ramps and Doors categories.
Note 2: The IsExternal property applicable to (IFC4.3 version):
An easy way to find more information: https://search.bsdd.buildingsmart.org/



