For all BIM packages, you have to make sure that there is a room, space or zone volume assigned to all areas within the building envelope. This includes lifts, stair, riser spaces and ceiling voids making sure that there are no air gaps within it. If this is not adhered to, the result will be external air gaps to internal areas of the building model and rooms missing from the analysis creating inaccurate results.
If you get either of the warnings below, the boundary of that area in the model will need to be addressed for gaps
