Simulations of Indoor Air Quality and Ventilation Impacts of Demand Controlled Ventilation in Commercial and Institutional Buildings

Carbon-dioxide (CO2) based demand controlled ventilation (DCV) offers the potential for more energy efficient building ventilation compared with constant ventilation rates based on design occupancy. A number of questions related to CO2 DCV exist regarding energy benefits, optimal control strategies, and indoor air quality impacts for contaminants with source strengths that are independent of the number of occupants. In order to obtain insight into these issues, a simulation study was performed in six commercial and institutional building spaces. This paper reports on one of the spaces, a lecture hall, in which six different ventilation strategies were compared, three of them using CO2 DCV. The results depend on occupancy patterns, design ventilation rate and ventilation system operating schedule as well as assumed contaminant source strengths and system-off infiltration rates. In these simulations, CO2 DCV resulted in significant decreases in ventilation rates and energy loads accompanied by increased indoor CO2 and volatile organic compound (VOC) concentrations. The increases in CO2 were generally in the range of 300 mg/m. The VOC levels increased by a factor of two or three, but the absolute concentrations were still low. The annual energy load reductions with CO2 control ranged from about 50 % to 75 % depending on the space type, climate and ventilation strategy.