I have the floor plan of a four-floor building. I need a 3D CAD model of the floors on top of each other that can be used for HVAC CFD modeling (a Volume for air, and volumes for the doors, windows, walls, and roofs). I have done the top floor, but for others, I face difficulty with connecting the volumes to each other. I think it needs a little touch up for the floor plans before creating the 3D model. Please let me know if you can help me with this quickly.