Demand-controlled ventilation in new residential buildings: Consequences on indoor air quality and energy savings

Abstract

The consequences on indoor air quality (IAQ) and potential of energy savings when using a variable air volume (VAV) ventilation system were studied in a newly built Swedish building. Computer simulations with IDA Indoor Climate and Energy 4 (ICE) and analytical models were used to study the IAQ and energy savings when switching the ventilation flow from 0.375 l·s−1·m−2 to 0.100 l·s−1·m−2 during unoccupancy. To investigate whether decreasing the ventilation rate to 0.1 l·s−1·m−2 during unoccupancy, based on Swedish building regulations, BBR, is acceptable and how long the reduction can last for an acceptable IAQ, four strategies with different VAV durations were proposed. This study revealed that decreasing the flow rate to 0.1 l·s−1·m−2 for more than 4 h in an unoccupied newly built building creates unacceptable IAQ in terms of volatile organic compounds concentration. Hence, if the duration of unoccupancy in the building is more than 4 h, it is recommended to increase the ventilation rate from 0.100 l·s−1·m−2 to 0.375 l·s−1·m−2 before the home is occupied. The study showed that when the investigated building was vacant for 10 h during weekdays, increasing the ventilation rate 2 h before occupants arrive home (low ventilation rate for 8 h) creates acceptable IAQ conditions. In this system, the heating requirements for ventilation air and electricity consumption for the ventilation fan were decreased by 20% and 30%, respectively.