windows and shading when walls are thick?

[Han99]

I am currently modelling a building with shading on some of the windows. All windows have a significant reveal due to the thickness of the wall. I am wondering whether to model the full thickness of the shading (wall depth plus shading) or only the shading exterior to wall. (e.g. if wall is 0.4m thick and shading protrudes the wall by 0.2m, do I add a shading depth of 0.6m or 0.2m around the windows.

I guess the fundamental question is: Does IES account for the construction thickness of walls compared to the windows when running daylighting and overheating analysis. If this is the case, I would expect to add the full 0.6m of shading. If not I would add only 0.2m of shading.