A series of field studies on the performance of displacement ventilation (DV) were carried out in schools across Canada during the heating season over the last three years. Indoor air quality was evaluated using the IAQ index Contaminant Removal Effectiveness (CRE) based on carbon dioxide concentrations for three schools equipped with DV systems. Results from the three field studies have shown values of CRE to be higher than 0.7 (ventilation effectiveness specified in ASHRAE 62.1-2007 when DV systems are used for heating, with ceiling return). The measured CRE in the three schools was often greater than 1.0 even in the middle of the heating season. The results show that as long as the supply air is cooler than the room air, DV system works well in achieving good contaminant stratification and ventilation effectiveness in the space when combined with a perimeter heating system.