Indoor heat conditions measured in urban slum and rural village housing in West Bengal, India

This study uses multivariate statistical analyses to identify building and behavioral factors associated with indoor heat stress in dwellings located in Kolkata slums and a rural village in West Bengal, India - residential areas whose summertime heat experiences have been sporadically studied and inconsistently quantified. During the summer of 2019, indoor temperature, humidity and heat stress index were monitored every 10 min over a 24-h period in 123 slum dwellings in Kolkata and in 101 rural village houses located about 75 km south of Kolkata; and compared to outdoor measurements. Most dwellings exhibited indoor conditions that were above those considered safe for occupants at some point during the day. However, under similar outdoor conditions, indoor heat stress was greater and more prolonged in Kolkata slum dwellings than in rural village houses. The coolest dwellings were constructed of mud walls and thatch roofs in the village, and the hottest dwellings were constructed of cement walls and clay tile or corrugated tin roofs in Kolkata. In the Kolkata slums, the duration of dangerous heat stress during the day was inversely related to the number of rooms in a dwelling, and positively related to the number of occupants. Binary logistic regression analysis showed that crowding and construction materials in Kolkata slums contribute to dangerous indoor HSI levels even at relatively low outdoor maximum temperatures. Further studies using this relatively simple and easily applied protocol can effectively increase the limited data on indoor conditions in understudied urban slum and rural village conditions in India.