IFC Export from DirectShape Elements

Hi, 

I've converted walls, doors, and windows elements to DirectShape as described in Jeremy's blog. Thank you, Jeremy. It worked great so far

http://thebuildingcoder.typepad.com/blog/2015/11/flatten-all-elements-to-directshape.html

After converting elements into DirectShape I exported the model into IFC, and I realized that only Wall elements are exported remaining void volumes for doors and windows. Doors and windows are not exported at all as IFC elements. Is this happened because it lost the dependancy of models between the host elements and family instances? Please let me know if you know any information reagarding this issue. 

Thanks,

Jinsol