Outdoor thermal comfort and summer PET range: A field study in tropical city Dhaka

Abstract

Urban microclimate has important consequences on the thermal sensation of pedestrians. However, the extent of this effect may vary as other parameters such as respondents’ personal factors, psychological and behavioural aspects and cultural backgrounds may be involved. This heightens the need for subjective assessment and on-site questionnaire surveys alongside objective field measurements to understand outdoor comfort conditions which is essential for creating sustainable urban spaces. In this study thermal comfort conditions outdoors are examined through field surveys in the high-density, tropical city Dhaka, where extensive microclimatic monitoring has been carried out in parallel to subjective responses of the pedestrians. Microclimatic conditions, which are affected by the urban geometry, are found to be statistically correlated with thermal sensation votes (TSV), with air temperature, globe temperature and mean radiant temperature being the most important parameters (correlation coefficients of r = 0.47, 0.45 and 0.44 respectively). The study also reports the effect of urban geometry parameters on microclimatic conditions, identifying strong correlations with globe temperature (r = −0.50), mean radiant temperature (r = −0.48) and wind speed (r = 0.72). Furthermore, the study proposes acceptable ranges (upper limits) for PET for the tropical climate of Dhaka with a ‘Neutral’ range between 29.5° and 32.5 °C confirming that people in outdoor conditions will feel comfortable at a higher PET range.