Dear All,

According to ASHRAE 90.1 - 2010 mandatory provision Zone Isolation, "HVAC systems serving zones that are intended to operate or be occupied nonsimultaneously shall be divided into isolation areas. Zones may be grouped into a single isolation area provided it does not exceed 25,000 ft2 of conditioned floor area nor include more than one floor. Each isolation area shall be equipped with isolation devices capable of automatically shutting off the supply of conditioned air and outdoor air to and exhaust air from the area".

In the context of a hotel project which has fully vertical air distribution (1 ventilation shaft per group of vertically aligned rooms), compliance with this mandatory provision would imply the specification of motorized dampers in each guest room, what leads to a very high capital investment. Considering the fact that outdoor air supply is not actively thermally treated, savings associated with zone isolation are not very relevant.

Taking into account the specificities referred above, is there any exemption or alterative compliance path to this requirement?