Energy and ventilation performance analysis for CO₂-based demand-controlled ventilation in multiple-zone VAV systems with fan-powered terminal units (ASHRAE RP-1819)

CO2-based demand-controlled ventilation (DCV) has been proved to be energy-efficient by altering ventilation rates according to surrogated indications of CO2 levels in single- and multiple-zone single-path variable air volume (VAV) systems. However, DCV for multiple-zone VAV systems with multiple recirculation paths is still untapped. Multiple-zone VAV systems with series and parallel fan-powered terminal units (FPTUs) are studied in this study. Energy and ventilation performance of the DCV strategies with dynamic resets are evaluated. The DCV control sequences for FPTUs are first summarized. A co-simulation approach combining EnergyPlus with CONTAM is adopted. The DCV controls are implemented in the EnergyPlus energy management system (EMS) module. New EnergyPlus EMS actuators are added and a customized EnergyPlus module is built to achieve the DCV control for each system. An office building is used to demonstrate the benefits from the proposed DCV strategies in four different U.S. climates zones. Two baselines for ventilation requirements (ASHRAE 62.1, California Title 24) are considered. The proposed DCV strategies resulted in 7–14% and 7–21% HVAC energy savings for each system, on a source energy basis, compared with the baseline of a simplified ASHRAE 62.1 approach. Both systems could achieve good compliance with the ventilation requirements in ASHRAE Standard 62.1.