Analysis of thermal bioclimate in various urban configurations in Athens, Greece

Abstract

The present study deals with human thermal comfort, as it is quantified by two well-known human biometeorological indices, Physiologically Equivalent Temperature (PET) and Humidex, in selected urban areas with different tree and building structures. The study took place during July 2003, at Agricultural University of Athens, Greece. Meteorological and environmental measurements were carried out at six sites. The selected sites differ in regard to sky view factor (SVF) values, environmental configuration and green (vegetation) coverage. The results of this study indicate a striking influence of site config- uration on human thermal comfort. For example, in an outdoor lawn area surrounded by trees (green atrium) the PET was greater than 41 °C (human perception of "very hot") for 13 % of the measurement time, while in an open building atrium (courtyard) PET was greater than 41 °C for 28 % of the time. In addition, 'comfortable' conditions as PET quantifies formed during 26 % of the measurement time in green atrium but less than 15 % of the time in the building atrium. Especially during daytime the difference between these two sites reached 8.7 °C according to the PETand 4.3 °C according to the Humidex. At sites with low SVF values and dense green coverage the human biometeorological conditions were improved compared to sites with high SVF values and those with buildings nearby. Significant relationships between SVF and biometeorological indices classes were indicated. The PET index better represented human comfort than Humidex.