Acceptable indoor air quality at reduced energy consumption for high-occupancy buildings with intermittent operation

In high-occupancy buildings with intermittent and short-occupancy events, occupants and their activities are the primary sources of contaminants, rendering continuous ventilation unnecessary for achieving acceptable indoor air quality (IAQ). Because the recommended ventilation rate constitutes a substantial percentage of the supply air, reducing or discontinuing ventilation during unoccupied periods saves significant energy. This study aims to assess the IAQ of high-occupancy buildings with different ventilation strategies and occupancy schemes to conserve energy using CONTAM (IAQ and ventilation analysis program) and Visual-DOE (energy analysis program). The results show that intermittently operating the ventilation 1 hour before occupancy saves 25% in the auditorium and 33% in the mosque compared to the continuous ventilation strategy. The intermittently operated strategy with ventilation 1 hour before occupancy also revealed an acceptable CO₂ level (<1000ppm), while the Formaldehyde (HCHO) levels decreased with increasing ventilation rates, as humans’ contribution to the HCHO concentration indoors was insignificant.