Mono-pitch roofs at different heights supported by load-bearing wall

Question

I have a school building to model using CAD input methodology. 
 It has a central load-bearing timber-frame wall supporting the ends of two mono-pitch roofs positioned at different heights. The wall between the top roof and lower roof is exposed and contains windows. 
 Below the lower roof the wall is an internal stud partition. The building is has a common ground-floor with no intermediate floors. 
 When I try to model the building and set up the roofs using the 'extend walls to underside of roof' command, the wall is rendered as an internal wall up to the top roof level. How can I model this wall to be exposed between the two roofs and not exposed internally? Any help much appreciated.

Shane Regan · Answer

Hi Alan, 
 This can be tricky to achieve however there are a few options - please see guidance here. An additional option may be to use vertical roof sections, if appropriate in this instance. The most valid method will be largely be determined by what calculations you wish to perform however. 
 Going forward, Hevacomp calculations are being transitioned over to OpenBuildings Energy Simulator. This offers much improved 3D modelling capabilities where this should be much simpler to achieve.