Thanks for the quick reply. I did use the incompressible model for buoyancy driven flow.
Anyways, I'm just playing with the software right now. The aim was to model a room with displacement ventilation, radiant floor heating, a cold window and occupants. I was really hoping to be able to model the CO2 levels in the space. I'm trying to see if I could use this tool at work before I pitch getting a license to my boss.