For single supply systems, where the air supplied to a ventilation zone is a mixture of outdoor air and system-level recirculated air, zone ventilation efficiency (Evz
) shall be determined in accordance with Equation 404.3.1. Examples of single supply systems include constant-volume reheat, singleduct VAV, single-fan dual-duct
, and multizone systems.
Evz = 1+Xs—Zpz
The average outdoor air fraction for the system (Xs) shall be determined in accordance with Equation 404.2 and the primary outdoor air fraction for the zone (Zpz) shall be determined in accordance with Section 403.5.1. [ASHRAE 62.1:A1.2.1]