Heat stress in urban areas: Indoor and outdoor temperatures in different urban structure types and subjectively reported well-being during a heat wave in the city of Leipzig
Franck, Ulrich; Krüger, Michael; Schwarz, Nina; Grossmann, Katrin; Röder, Stefan; Schlink, Uwe
Climate projections for Leipzig suggest elevated minimum and maximum temperatures as well as more frequent days with high temperatures. Hence, climate change is threatening human well-being and health. People spend the majority of their time indoors. Therefore, indoor temperatures (especially during the night) are of special importance with respect to well-being and health. Indoor air temperature depends on outdoor air temperatures, but is for example modified by type of urban structure, housing area, and may be also influenced by differences in the behavior of the inhabitants. Especially in cities, outdoor air temperatures depend on urban structure e.g. housing density, building arrangement, unpaved areas, types of urban structures, urban green, and other factors. Hence, the questions arise how types of urban structures are related to inner-urban temperature differences and how outdoor air temperatures influence indoor temperatures in dependence on urban housing conditions. This work is a part of a pilot study conducted during the summer 2010 which gathered data from remote sensing, mobile measurements, stationary measurements of air temperatures and relative humidity in areas with different housing structures, and of indoor as well as outdoor temperatures in occupied apartments. Household-survey data reported the subjective perception of heat stress. The study resulted in rather complex relationships between type of housing areas, indoor and outdoor temperatures, morning and evening temperatures, indoor and outdoor temperatures as well as subjective heat perception. Green spaces and types of residential areas are related to air temperatures. More green resulted in lower temperatures. Temperatures have a tendency to increase with increasing story number and are significantly higher in the top floor. An indoor heat island effect corresponding to the outdoor effect could be shown for the homes: Distance to city center is a predicting variable for both outdoor and indoor air temperatures. The subjective feeling of heat strain did not clearly reflect measured temperature differences but varies according to adaptation behavior. Indoor evening temperatures are most strongly related to heat perception. Indoor and outdoor temperatures are not clearly correlated because of several modifying factors. The results of this study underline the importance of conservation and development of building structures and types of urban structures which stay abreast of changes by global warming. In this context, special attention has to be paid to indoor temperatures.