Sets the value of OverallWidth attribute. This attribute represents overall measure of the width, it reflects the X Dimension of a bounding box, enclosing the window opening. If omitted, the OverallWidth should be taken from the geometric representation of the IfcOpening in which the window is inserted.

The body of the window might be wider then the window opening (for example in cases where the window lining includes a casing). In these cases the OverallWidth is still specified as the window opening width, and not as the total width of the window lining.