ML-11-027 -- Pollutant Removal Effectiveness with Underfloor Air Distribution: Field Study of a Ducted Variable-Flow System PDF

Underfloor air distribution (UFAD) systems have been more widely used over the past decade. UFAD systems are believed to provide better CO2 extraction, reduced energy use, improved occupant satisfaction with thermal comfort, and easier reconfiguration relative to conventional overhead mixing ventilation (MV) systems, but relatively few field evaluations have been reported. One metric used in evaluating ventilation performance is pollutant removal effectiveness using CO2 as the tracer gas. A field study found in the literature determined that pollutant removal effectiveness was poorer than expected for a constant flow system in a LEED 1.0 commercial new construction pilot office building. This paper reports a field study of pollutant removal effectiveness and CO2 concentration at breathing level with a ducted variable-air-volume (VAV) UFAD system in a LEED platinum building. A variety of occupancy densities, diffuser locations, and room types were evaluated. Overall, the performance of the UFAD was better than reported for the previously reported constant flow system. The characteristics of the spaces and conditions during measurement are compared with those in the previous study. Factors affecting differences in performance for the two systems are discussed.