As our industry continues to adopt more advanced building information modeling (BIM) techniques, and more data is becoming available that can be automatically read, compared, and manipulated. Software can now determine space type, loads, and adjacencies directly from an architect’s model. This technological shift allows zoning to be automatically determined for a given model. Unfortunately, the preeminent source for HVAC design, “The ASHRAE Fundamentals Handbook.” has this to say about zoning: “… a truly automated, one-size-fits-all approach remains to be developed.”
This article will focus on multi-zone variable airflow volume with reheat (VAV) systems. In this system, a central air moving unit — commonly referred to as an air handling unit (AHU) or rooftop unit (RTU) — returns air from multiple spaces, mixes it with outdoor air, filters it, then heats or cools as necessary to provide air to a VAV unit. That unit then modulates the flow of air to the spaces and reheats it as necessary to meet a space temperature set point.