A window panel is a casement, that is, a component, fixed or opening, consisting essentially of a frame and the infilling. The infilling of a window panel is normally glazing. The way of operation is defined in the operation type.

The IfcWindowPanelProperties are used to parametrically describe the shape and operation of window panels. The parametric definition can be added solely or additionally to the explicit shape representation of the window. 

The IfcWindowType can define windows consisting of more then one panel. In this case, one instance of IfcWindowPanelProperties has to be included for each window panel. The PanelPosition attribute, in conjunction with the IfcWindowType.OperationType attribute, determines to which panel the _IfcWindowPanelProperties_apply. The IfcWindowPanelProperties are included in the list of properties (HasPropertySets) of the IfcWindowStyle. More information about the window panel can be included in the same list of the IfcWindowType using the IfcPropertySet for dynamic extensions. The image below shows the panel that is applied to the position within the lining as defined by the panel position attribute.