In a multi-zone system with 100% outdoor air, outdoor air delivery to zones is allocated based on which parameter?

• A. Zone area
• B. Occupant density by zone
• C. Voz values
• D. Time of day

Answer: (C)

In a multi-zone system that uses 100% outdoor air, outdoor air delivery to each zone is determined by how much outdoor air that zone requires to meet ventilation standards, expressed as Voz. Voz represents the zone’s required outdoor airflow to satisfy the ventilation rate for that space under ASHRAE 62.1. Because the system is delivering only outdoor air, the total supply is divided among zones in proportion to their Voz values, ensuring every zone receives the amount of outdoor air it needs.

Think of Voz as the design fingerprint for each zone’s ventilation: it captures the zone’s occupancy and activity level, and the corresponding ventilation requirement. Zone area or occupant density by itself isn’t the direct basis for the allocation, since Voz already encodes those needs into a single design value. Time of day isn’t used to split the fixed 100% outdoor air flow among zones in this setup; the allocation is constant, scaled by the Voz for each zone.