Which describes DCV in 62.1?

• A. DCV means delivering a fixed outdoor air rate at all times.
• B. DCV reduces energy use by not monitoring occupancy or IAQ.
• C. DCV modulates outdoor air delivery based on occupancy or IAQ indicators to meet IAQ targets efficiently.
• D. DCV is only used when IAQ is not a concern.

Answer: (C)

Demand-controlled ventilation adjusts the outdoor air delivered by the system based on actual need, using occupancy or IAQ signals to guide how much fresh air is brought in. The goal is to meet the indoor air quality targets efficiently while not over-ventilating. By responding to sensors such as CO2 (a common occupancy proxy) or other IAQ indicators, the system can lower outdoor air when spaces are sparsely occupied or IAQ is already acceptable, and raise it when higher ventilation is needed. This energy-saving approach is what 62.1 describes.

Providing a fixed outdoor air rate at all times ignores real-time conditions and wastes energy, so that’s not DCV. Not monitoring occupancy or IAQ is the opposite of DCV’s purpose, which relies on those signals to control ventilation. And DCV is not reserved only for times when IAQ is not a concern; it’s specifically about using signals to maintain IAQ targets efficiently, adjusting ventilation as conditions change.