According to 5.4.3.4 (mandatory provision) enclosed vestibules shall protect building entrances that separate the conditioned space from the exterior. In the building that I’m considering, a factory, a huge space is occupied for the production and it is conditioned. There are big doors where trucks can enter the building. Shall those entrances have enclosed vestibules or could some exception exclude them? Could air curtains (“air doors”) be used as alternative option? Since they would be used by trucks, the vestibules would occupy a big area. Regards