INDOOR AIR QUALITY AND ENERGY ISSUES OF VAV & VRF SYSTEMS

Abstract

With the global climate aggravating and conditioning the interior space in tropical nations not being scarce, it is of paramount importance to improve the energy efficiency of AC system in buildings. However, it becomes detrimental if IAQ is sacrificed at the expense of energy efficient AC systems. The building occupants’ perceived IAQ is of significant as they hold partly the power to alter the AC system’s operations. Therefore, their perceived IAQ ought to be accounted for. This research aims to provide practitioners more options in the selection of energy efficient AC system in a non-residential building while maintaining the essential IAQ. It is believed that VRF system is more energy efficient than VAV system. It is thus of interest to determine examine the energy usage distribution, IAQ, occupants’ perceived IAQ for a building operating with either VAV or VRF systems.

The information sought is gathered from simulation, field measurements, subjective assessment and interview where they represent quantitative and qualitative approaches of data collection.

However, the results show otherwise. VRF system expends 10% more energy than VAV system due to heavier fan power consumption than the latter. In terms of IAQ, both systems display results that are typically below the limits of acceptability of SS554:2009 and relatively common trends. Variations of profile for each IAQ parameter are supported by literature. Furthermore, respondents’ perceived IAQ generally meet the target of 80% satisfactory level. Possible counteracts to reduce the PPD are denoted in their respective sections. AC systems are capable of achieving the desired level of IAQ and perceived IAQ with the appropriate design.