Energy saving potential of occupancy-driven air rates and schedules in an open-office with variable occupant density

Tempering outdoor air to ventilate buildings can represent a significant portion of total building energy use in climates with cold winters, hot summers, or high humidity. In these climates demand control ventilation is a relatively simple strategy to avoid over-ventilation and increase energy efficiency. In this study baseline energy demand was evaluated through a combination of psychrometric and statistical means and 4 alternative control scenarios were evaluated using the same methodology. The control scenarios were designed using data from high-accuracy people counting sensors installed in an open-plan office space suspected of having a highly variable occupant density. Net occupancy data was collected from these sensors in parallel with a range of heating ventilation and air conditioning telemetry to determine the degree of over-ventilation occurring under baseline conditions and the magnitude of savings achievable with the proposed alternative control scenarios. The study suggests that tuning ventilation rates to directly measured occupant density and space utilization patterns can reduce ventilation energy demand by over 70%. Findings also suggest that a significant portion of all possible savings can be achieved without real-time integration with a building's control systems, implying a wide range of buildings may benefit from access to empirically determined space use data.