title: Assessment of indoor heat stress variability in summer and during heat warnings: a case study using the UTCI in Berlin, Germany.
abstract: Humans spend most of their time in confined spaces and are hence primarily exposed to the direct influence of indoor climate. The Universal Thermal Climate Index (UTCI) was obtained in 31 rooms (eight buildings) in Berlin, Germany, during summer 2013 and 2014. The indoor UTCI was determined from measurements of both air temperature and relative humidity and from data of mean radiant temperature and air velocity, which were either measured or modeled. The associated outdoor UTCI was obtained through facade measurements of air temperature and relative humidity, simulation of mean radiant temperature, and wind data from a central weather station. The results show that all rooms experienced heat stress according to UTCI levels, especially during heat waves. Indoor UTCI varied up to 6.6 K within the city and up to 7 K within building. Heat stress either during day or at night occurred on 35 % of all days. By comparing the day and night thermal loads, we identified maximum values above the 32 °C threshold for strong heat stress during the nighttime. Outdoor UTCI based on facade measurements provided no better explanation of indoor UTCI variability than the central weather station. In contrast, we found a stronger relationship of outdoor air temperature and indoor air temperature. Building characteristics, such as the floor level or window area, influenced indoor heat stress ambiguously. We conclude that indoor heat stress is a major hazard, and more effort toward understanding the causes and creating effective countermeasures is needed.
authors.affiliation: Geography Department, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099, Berlin, Germany. nadine.walikewitz@geo.hu-berlin.de.
authors.forename: Nadine
authors.initials: N
authors.lastname: Walikewitz
authors.affiliation: Department of Ecology, Technische Universität Berlin, Rothenburgstraße 12, 12165, Berlin, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Jänicke
authors.affiliation: Federal Environment Agency (Umweltbundesamt), Wörlitzer Platz 1, 06844, Dessau-Roßlau, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Langner
authors.affiliation: Geography Department, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099, Berlin, Germany.
authors.forename: Wilfried
authors.initials: W
authors.lastname: Endlicher
mesh_terms: D001604:Berlin / Q000453:epidemiology; D002980:Climate; D018882:Heat Stress Disorders / Q000453:epidemiology*; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D006813:Humidity; D012621:Seasons
keywords: Heat stress; Indoor climate; Indoor measurements; UTCI