In a typical commercial building, ventilation systems run at fixed rates determined by peak design occupancy — regardless of how many people are actually in the space at any given moment. On an average weekday, this means most zones are being over-ventilated for the majority of the working day, consuming energy, over-cooling occupied spaces, and generating unnecessary carbon emissions.
Demand-controlled ventilation (DCV) solves this by making ventilation delivery dynamic — using real-time CO₂ concentration and occupancy data to modulate airflow zone by zone, delivering exactly the fresh air needed and nothing more.
The Technical Case
CO₂ is a reliable proxy for occupant load in enclosed spaces. When CO₂ rises above 800ppm in a zone, the AHU’s VAV damper opens to increase fresh air delivery. When occupancy drops and CO₂ falls, the damper closes proportionally. The result is continuous, real-time optimisation of the building’s ventilation energy draw.
Properly implemented DCV typically delivers 25–40% reduction in AHU energy consumption compared to fixed-rate ventilation. In a 10,000 sq ft commercial floor plate, this can represent a saving of 15–30 MWh annually — and a proportional reduction in carbon emissions.
Integration with BMS
DCV requires CO₂ sensor deployment (one sensor per zone, typically every 100–150 sq m), integration with the building’s AHU control system via BACnet or Modbus, and a BMS setpoint strategy that defines CO₂ thresholds and ramp rates for each zone type.
The Prysm Edge Building Intelligence team can design, specify and commission DCV retrofits in occupied buildings, with minimal disruption to operations. Contact us to discuss a feasibility assessment for your estate.
