Field investigation of comfort temperature in Indian office buildings: A case of Chennai and Hyderabad

Abstract India's building energy consumption is increasing rapidly. The subcontinent does not have custom made thermal comfort standards. There is little research in this field in the last 26 years. This leaves a lot to be investigated. We conducted a thermal comfort field study in 25 office buildings in Chennai and Hyderabad for seven months during the summer and south west monsoon seasons in 2012 and collected 2612 datasets from 1658 subjects. The comfort temperature in naturally ventilated (AC off) (NV) mode was 27.6 °C and 28.1 °C in Chennai and Hyderabad respectively. In air conditioned (AC) mode, it was 27.0 °C and 26.1 °C in these two cities. These departed from the limits in the Indian National Building Code. Chennai recorded significantly higher indoor air speeds and thus higher comfort temperature. In 71% cases the air speed was less than 0.15 m/s, underscoring the need for improvement. A majority always sensed the air movement low and desired increased air speeds, despite voting comfortable. Both the States grappled with daily outages throughout the survey period. All the buildings, excepting two were forced to run without the AC at least for 2 h daily, while none were prepared well for this. Several design and non-design factors seriously impeded environmental adaptation in buildings, limiting the adaptive operation of windows and fans. Consequentially, thermal acceptability was generally low (62.5%). This calls for architect's serious attention towards environmental and thermal adaptation in buildings, in the era of power paucity and prudent consumption.