I know very little about IFC.

Geometry Gym sells a plugin for IFC for Rhino, for $. http://www.rhinojungle.com/video/geometry-gym-plugin

"Envisioneer (version 9) now exports its basic model structure to an IFC file for use with other applications..."


http://www.slideshare.net/metalalp/building-information-modeling-bim-industry-foundation-classes-ifc-presentation

- Brian

There is ruby code for sketchup and BIM/IFC which may have some clues?
http://code.google.com/p/bim-tools/