Abstract
This study investigates indoor thermal comfort during heatwaves in dwellings of the Southern European city of Pamplona, Spain. Utilizing K-means and Hierarchical clustering, it explores clustering patterns from occupants' survey responses (n = 189) to thermal comfort-related questions (i.e. day and night thermal sensation, thermal satisfaction and thermal preference) as well as causal links (i.e. indoor temperatures, building/occupant features) and consequences (i.e. sleep quality, heat-related symptoms) of such clusterings. Both unsupervised learning techniques coherently revealed two groups: the comfortable and uncomfortable clusters. Uncomfortable occupants coherently experience more sensation to heat, greater preference for cooler temperatures, and more thermal dissatisfaction, especially during daytime hours. Dwellings of comfortable occupants experience median indoor temperatures around 26ºC during both non-heatwave and heatwave periods; dwellings of uncomfortable occupants equal or above 27ºC. Discomfort or overheating—coherently expressed by the thermally uncomfortable cluster—is alleviated by multiple factors related to the presence of active cooling technologies in all rooms, use of passive and low-energy cooling measures (e,g. fans), and higher income; exacerbated by heatwave conditions, larger household sizes, and being a woman. As coherently expressed by the uncomfortable cluster heat worsens the sleep quality of occupants (3 to 6-fold) and increases the likelihood of occupants to experience heat-related symptoms (17 to 19-fold). This study is particularly important to policymakers, as it sheds light, from dwellers’ first-hand experience in a Southern Europe city, on relevant factors that should be taken in consideration to allow them to cope better with heatwaves without compromising their comfort and health.