Minimum sensor grid density and configuration to enable CO2-based demand-controlled ventilation in an office building

CO2-based demand-controlled ventilation (DCV) requires placement of CO2 sensors in air handling units (AHUs) as well as in individual zones. In complex multi-zone systems or across building portfolios, the installation and maintenance costs of these sensors are non-negligible. This study explores how CO2 sensor grids can be configured in a sparser manner to allow for CO2-based DCV of spaces adjacent to zones with CO2 sensors that may not have sensing infrastructure themselves. A simulation-based study of a 26-zone office building was conducted under a variety of occupancy schedules, number and placement of zone-level CO2 sensors, and with and without motion detectors to determine how RP-1747 DCV impacted heating, ventilation, and air conditioning (HVAC) energy use and zone CO2 concentrations when implemented traditionally or with adjacent control, for a total of 29,730 simulations. It was found that CO2 sensors installed in approximately 31% of zones could effectively enable CO2-based DCV across the entire floor plate with a negligible impact on the number of hours where CO2 concentrations were elevated, resulting in 7.3% to 17.4% higher HVAC energy savings compared to individual control of spaces in the case study building.