How do buildings adapt to changing occupancy? A natural experiment

Most office buildings regulate their indoor climate through conservative setpoints and schedules based on maximum occupancy. However, the occupancy of most office buildings rarely exceeds 50%. Buildings' lack of adaptability to partial occupancy exacts a toll on their energy use by providing building services excessively and inefficiently. Largely vacant office buildings left in the wake of the COVID-19 pandemic present a natural experiment to evaluate the extent of this problem. Three-parameter univariate changepoint models were employed to estimate the change in energy use before and during the pandemic in two institutional office buildings: one with occupancy-based ventilation, and one with traditional ventilation. A calibrated energy model was developed for the traditional building to determine how much energy could have been saved if occupancy-based ventilation was implemented. It was found that the building could have saved up to 32% and 12% for heating and cooling, respectively, in the pre-pandemic period alone.