International Journal of Biometeorology

, Volume 62, Issue 1, pp 29–42 | Cite as

Assessment of indoor heat stress variability in summer and during heat warnings: a case study using the UTCI in Berlin, Germany

  • Nadine Walikewitz
  • Britta Jänicke
  • Marcel Langner
  • Wilfried Endlicher
Students and New Professionals 2015


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.


Indoor climate Heat stress UTCI Indoor measurements 



We would like to thank the German research foundation (DFG) for funding Research Unit 1736 “Urban Climate and Heat stress in mid-latitude cities in view of climate change (UCaHS)” (EN138/21-1, SCHE 750/8-1 and SCHE 750/9-1) and Phillip Schuster for his support with data collection.


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Copyright information

© ISB 2015

Authors and Affiliations

  • Nadine Walikewitz
    • 1
  • Britta Jänicke
    • 2
  • Marcel Langner
    • 3
  • Wilfried Endlicher
    • 1
  1. 1.Geography DepartmentHumboldt-Universität zu BerlinBerlinGermany
  2. 2.Department of EcologyTechnische Universität BerlinBerlinGermany
  3. 3.Federal Environment Agency (Umweltbundesamt)Dessau-RoßlauGermany

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