Openings tab in model data under Vents
On surfaces where no custom openings have been defined, you can create vents simply by checking the 'Vents fitted?' options under the External and Internal Vents headers. In this case vents are positioned on each surface using 'Vent spacing' and 'Vent height above floor' in the automatically generated facade layout. Typically, a single vent is positioned under each of the windows (if the vent spacing is the same as the window spacing).