Center for the Built Environment

Room air stratification (RAS) is one of the key features of UFAD technology that determines how the benefits of low energy, good indoor comfort and ventilation performance are achieved. Understanding, accounting for, and controlling RAS are essential to successful design, installation, and operation of these systems. Likewise, modeling RAS is essential to simulating the energy performance of these systems. Although much research has been focused on RAS for displacement ventilation systems, relatively little has been done to develop a comprehensive model for UFAD systems, and no models currently exist within energy simulation programs commonly used by design and installation practitioners. Development of a model for RAS must be based on sound physical principles as well as also accurately representing the reality of how these systems are installed and operated. That is the purpose of the full scale testing effort we describe in this report.

CBE has been involved in RAS research for several years, and the work reported here can be considered an expansion and improvement over earlier work in CBE’s environmental chamber and that performed in partnership with York International at the McGrath Laboratory in St. Louis MO from 2000 and 2001. [Webster, et. al. 2001] The work reported here was conducted between January 2003 and November 2004 in the York Air Distribution Research Facility (ADRF) in York, PA. The full scale testing work was conducted in close collaboration with other elements of this project as described in the final report. [Bauman et. al. 2006] Additional material about UFAD technology can be found in the ASHRAE underfloor design guide [Bauman 2003].