Experimental Study of Thermal Comfort in an Office Environment with an Underfloor Ventilation System

Abstract

Frequent changes in arrangement in office space and the huge amount of cables brought about by the extensive use of computers make the implementation of raised flooring a necessity in modern office buildings. Underfloor ventilation systems that make use of the underfloor plenum for conditioned air distribution will therefore increase in popularity as they extend the flexibility of building services and take advantage of the raised floor to accommodate the HVAC system. Previous research has revealed that the top return type underfloor system saves a significant amount of energy, as the supply air temperature can be higher than that in a ceiling-based system. However, thermal discomfort due to temperature non-uniformity was also reported. This paper presents the experiment results of a laboratory study of the thermal performance for a floor return (FR) type underfloor system under different heat load densities and supply air temperatures. Vertical temperature differences and air velocities were found to be within the comfort limits stated in major international standards. The measured predicted mean vote and predicted percentage of dissatisfied values also satisfied the ISO Standard 7730. A comfortable environment was maintained by the FR type system under a dense internal heat load and with the supply air temperature set at as high as 18°C.