How do I select a VAV terminal unit for a zone?

VAV terminal unit selection starts with the zone's peak cooling airflow requirement (CFM or L/s), which is determined by the zone load calculation per ASHRAE Standard 62.1 ventilation requirements and ASHRAE 90.1 energy limits. The VAV box should be sized so the peak airflow falls between 60–80% of the unit's maximum capacity to ensure good turndown and avoid excessive noise at design conditions. Key selection parameters include inlet size (typically 4–16 inches round), heating coil capacity (if series fan-powered or reheat), sound power levels (NC rating), and control type — pressure-independent VAV controllers with DDC are now required by ASHRAE 90.1-2019 for most applications. Products like the JCI/Titus DESV or Trane VariTrane series provide selection software that automates discharge sound calculations.