demandcontrolled

Demand-controlled, in the context of building systems, refers to a control approach that adjusts ventilation rates and related outputs based on real-time measurements of demand rather than fixed schedules or constant airflow. The primary goal is to maintain acceptable indoor air quality while reducing energy use and equipment wear.

In practice, DCV commonly uses sensors such as carbon dioxide (CO2) sensors as proxies for occupancy, along with occupancy sensors and sometimes IAQ indicators like VOCs or humidity. When CO2 levels rise toward a predefined threshold, the system increases outdoor air intake; as levels fall, ventilation is reduced. The control logic is often applied to variable-air-volume (VAV) boxes, rooftop units, or dedicated outdoor air systems and is integrated with building management systems. DCV implementations may combine occupancy data with IAQ measurements and operate within standards or guidelines from organizations such as ASHRAE.

Applications are widespread in commercial buildings, including offices, schools, retail spaces, and healthcare facilities, where occupancy can vary considerably. Benefits include energy savings from avoiding over-ventilation and improved indoor air quality by matching ventilation to actual need. Economic and environmental gains can also support demand-response programs and sustainability goals.

Challenges include ensuring sensor accuracy and proper placement, regular calibration and maintenance, and achieving reliable commissioning. CO2 is a proxy for occupancy and may not capture all IAQ concerns, and there can be lags between occupancy changes and sensor response. Successful DCV relies on robust system integration, appropriate minimum ventilation settings, and ongoing verification of performance.