Thermal comfort in naturally ventilated apartments in summer: Findings from a field study in Hyderabad, India

There is little thermal comfort research in residential environments reported from India. Energy consumption in Indian residential buildings is one of the highest, increasing at a phenomenal rate. Indian standards advocate two narrow ranges of temperatures for all building and climate types. In this context, a field study in summer and monsoon was conducted following Class-II protocols, for three months in 2008, in naturally ventilated apartment buildings in Hyderabad. Over a 100 subjects involved, giving 3962 datasets. In May, most of the subjects were uncomfortable, preferring a temperature on the cooler side of the neutrality, despite accepting their thermal environments. Thermal sensation, preference and acceptance improved in June and July as temperature receded. Humidity did not affect comfort sensation much, as summer was hot and dry. Conversely, increase in humidity adversely affected the thermal comfort in June. Adaptive use of controls resulted in moderate air movement indoors, adequate for sweat evaporation most of the time. The subjects used traditional ensembles and slowed down their activities adaptively to restore thermal comfort. Clothing adaptation was found to be impeded by many socio-cultural and economic aspects. The comfort band (voting within -1 and +1) based on the regression analysis was found to be 26-32.45 °C with the neutral temperature at 29.23 °C. This is way above the limits (23-26 °C) set by Indian standards. The PMV was always found to be higher than the actual sensation vote. These findings have far reaching energy implications in a developing country like India.