Quantification of summertime thermal stress and PET range in a tropical Indian city

Abstract

Outdoor environments are rapidly deteriorating in tropical cities, affecting social and commercial activities. Thermal comfort plays a main role in encouraging people to use outdoor spaces. The present study evaluated objective and subjective measurements to assess outdoor thermal stress benchmarks (sensation, comfort and tolerance) in Nagpur city. Summertime micrometeorological surveys were conducted across 13 different locations which recorded 1445 respondents. Physiological equivalent temperature (PET) was used to evaluate objective thermal stress levels of respondents. Strong R2 (> 0.82) was found for PET against thermal sensation, comfort and tolerance. Neutral PET (NPET) was found to be 29.29 °C and NPET range as 26.33–32.25 °C. Thermal acceptability range (TAR) for 88% was found to be 24.61–34.52 °C. Neutral thermal comfort (NTC) and neutral thermal tolerance (NTT) were found to be 30.56 °C and 26.67° respectively using linear regression (LR). The range for NTC and NTT were 27.65–33.48 °C and 22.77–30.58 °C respectively. The study demonstrated higher tolerance of respondents towards extreme temperatures in hot dry climates when compared to those in temperate climates. The attributes of various benchmarks and ranges provide useful insights to optimize outdoor thermal environment and can contribute towards planning and designing sustainable cities.