Field Study Assessment of the Performance of Displacement Air Distribution in a Canadian School during the Heating Season

Stratified ventilation systems use a fundamentally different approach to supply heated or cooled air through a building than the ‘fully mixed and dilution’ ventilation systems found in the majority of non-residential buildings. Stratified air distribution creates a non-uniform environment in terms of temperature and pollutant distribution, and acceptable conditions in the occupied zone. Previous research has shown that this type of system works well for regions where buildings require year-round cooling. However there are a growing number of buildings using this approach in Canada, where buildings require heating during winter months. This paper presents results from a field study conducted in a school equipped with a displacement ventilation system. The results show that the measured contaminant removal efficiency (based on CO2 measurements) resulting from displacement ventilation in this case is better than that was predicted in previous studies for displacement ventilation under heating operation. In addition, key predictors of thermal comfort (the measured vertical air temperature difference and draft rating at ankle and head height) are also generally within the limits set by applicable ASHRAE standards.