[EN 16798-7:2017, 3.2]:conditioned space which can be considered as air flow independent from other conditioned spaces (i.e. the air leakages between two adjacent zones are sufficiently low to be neglected, and there is no possibility of air transfer between two zones)Note 1 to entry: A ventilation zone can be a set of rooms with enough air transfer between those rooms to consider they are all at the same pressure. It can also be a single room if there is no significant air transfer between this room and other ventilation zones.