Exploring the adequacy of mechanical ventilation for acceptable indoor air quality in office buildings

This paper explores how effectively building variable air volume air handling unit (VAV AHU) configurations supply required outdoor air to building spaces using data analysis and building performance simulation. One year’s worth of zone-level occupancy data from a floor of an institutional office building was estimated using Wi-Fi device count and concurrent motion detector and CO₂ sensor data. Zone-level ventilation rates were compared to these data to calculate per person ventilation rates. The results indicated that some spaces experienced under-ventilation for up to 34% of occupied hours. For the simulation-based investigation, a 27-zone energy model was used. Occupancy data from the building were used in the simulation. Four operation modes were simulated: default operation, occupancy-based demand-controlled ventilation (DCV), occupancy-based VAV control, and a combination of the latter strategies. The fewest instances of under-ventilation occurred with occupancy-based VAV control. The under-ventilation instances were a result of inefficient distribution of outdoor air across building zones. The supply of standard (10 L/s per person) ventilation with occupancy-based VAV control, instead of a default constant minimum ventilation rate, reduced the number of under-ventilation instances by ∼80% while reducing the energy use by ∼30%.