Performance evaluation and design guidelines for displacement ventilation.

This paper evaluates the performance of traditional displacement ventilation systems for small offices, large offices with partitions, classrooms, and industrial workshops under U.S. thermal and flow boundary conditions, such as a high cooling load. With proper design, displacement ventilation can maintain a thermally comfortable environment that has a low air velocity, a small temperature difference between the head and foot level, and a low percentage of dissatisfied people. Compared with conventional mixing ventilation, displacement ventilation may provide better indoor air quality in the occupied zone when the contaminant sources are associated with the heat sources. The mean age of air is younger, and the ventilation effectiveness is higher. Based on results from Scandinavian countries and the authors' investigation of U.S. buildings, this paper presents guidelines for designing displacement ventilation in the United States.