COMPARISON OF LEAKAGE CHARACTERISTICS IN AN ENVIRONMENT CHAMBER BETWEEN UNDER-FLOOR AIR DISTRIBUTION (UFAD) AND MIXING VENTILATION (MV) SYSTEM

Abstract

UFAD systems have shown to offer multiple benefits as compared to MV systems. UFAD systems do not only improve thermal comfort and IAQ, significant capital savings are also achieved through reduced floor-to-floor height in construction, minimized ducting and increased flexibility. In addition, using stratification to reduce cooling load requirements and reduced fan energy usage, UFAD systems have shown great energy savings potential. However, in practice, several issues have yet to be resolved, one of which is dealing with uncontrolled leakage from a pressurized under-floor plenum. Thus the objectives of this dissertation are to compare the leakage characteristics of UFAD and MV air distribution systems and recommend possible solutions to minimize air leakage. The research hypotheses are that with better sealing of the floor panels and electrical floor boxes, air leakage can be significantly reduce and UFAD system should reflect better thermal comfort and energy savings as compared to a MV system. This experiment based study is conducted in an environmental chamber in NUS. The experimental results have indicated that UFAD systems are more vulnerable to category 2 air leakages, which is air leaking into the occupied zone, whereas MV systems are exposed to category 1 air leakages in which air does not enter the occupied zone but escapes to neighboring zones or rooms. The results have proved that UFAD does have the potential to offer better thermal comfort and energy savings potential. In addition, the results have reflected a need to have a separate operating system for perimeter zones due to the dynamic solar loads experienced. This dissertation’s limitations come from lack of longitudinal quantitative data obtained from the air leakage tests due to lack of resources and the environmental chamber is not one specially built for UFAD systems. Recommendations to reduce air leakage for the underfloor plenum are also proposed.