Home office and quarantine indoors - How can we withstand the summer heat during the Corona pandemic?

Is Germany heading for yet another scorching summer? That’s what experts are warning. This will place yet another burden on the many people currently spending most of their time at home due to the coronavirus as they must now deal with lengthy hot spells in their own four walls. This underlines once again the importance of adapting urban districts and buildings to the new challenges of climate change. Together with various partners, the Leibniz Institute of Ecological Urban and Regional Development (IOER) is examining which measures are particularly suited to alleviate heat stress within the project HeatResilientCity.

balconies with various blinds and parasol

(Photo: H. Hensel/IÖR-Media)

Once again, Germany and Europe are facing an extremely hot summer. This was the warning issued last week by the World Meteorological Organization (WMO) of the United Nations. During the COVID-19 crisis, this will present unique challenges to cities and municipalities as well as individual citizens.

Home office has now become the norm for many people. Entire workforces are suddenly cooped up in their own four walls. Contact restrictions also mean that many citizens are forced to spend much of their day at home. Many pensioners are going outside less frequently to avoid getting infected with the coronavirus. The normal recommendation to visit cool places such as air-conditioned shopping centres or shady green spaces to escape overheated flats only has limited validity during the corona pandemic.

Yet long before COVID-19, we have known that long spells of summer heat can cause severe problems, especially in densely built-up areas. So how can cities adapt? Running until the beginning of 2021, the research project HeatResilientCity (German: Hitzeangepasste Stadt) aims to answer this question.

The spotlight on Gründerzeit buildings and prefabricated housing blocks

The investigations are focusing on two types of buildings that are very common in Germany and which house a large proportion of the population. These are, on the one hand, historic buildings from the 1850s to the early 20th century (the so-called Gründerzeit era) and, on the other hand, large-panel prefabricated blocks (German: Plattenbau). The latter are typical of many large housing estates built in Germany in the 1970s and 1980s. The project team is investigating how temperatures develop within flats in both types of buildings during long periods of summer heat and are considering which adaptation measures and combinations of measures could best reduce indoor overheating.

The scientists have measured temperature and humidity in order to specify the indoor climate of the buildings. Additional measurements have also been undertaken of the outdoor climate. This data is then used to configure dynamic thermal building simulations that closely reflect real-world conditions. These simulations, which form the core of the research work, can help identify structural deficiencies in buildings that make them particularly susceptible to summertime heating. In the cases under investigation, these are the window areas, the low heat storage capacity of attics and insufficient air exchange at night.

Building adaptation: Measures to alleviate heat stress

Project results already show that one of the most important measures to protect against overheating, particularly of flats on the upper floors, is better heat insulation of the roof and upper-floor ceilings. Triple-glazed windows can also help reduce solar irradiation from the intense summer sun. It is important that these windows can be fully opened to ensure sufficient night-time cooling. Rooms with large windows and thus more direct sunlight should also be fitted with exterior shading, for example external shutters or roller blinds. When renovating a building, heavy building components with a high thermal capacity should be used to upgrade roofing. The drawbacks of converted attics quickly become apparent in the summertime: they are particularly susceptible to overheating due to the lack of a thick layer of dense material that can store heat for many hours. Instead, the solar energy is quickly transferred from the roof surface to the interior.

The problem with the impending corona summer is that structural improvements cannot be made overnight. Furthermore, residents of rented flats and multi-family homes are reliant on the owner(s) viewing summertime overheating as a serious problem and taking appropriate action. Last but not least, the measures can be expensive. Not everyone can afford to pay the higher rents of such upgraded buildings.

Easy steps that everyone can take

The research project HeatResilientCity is also looking at steps that residents can themselves take to reduce heat stress in their own homes. The project team has already identified a range of diverse options. The key message is to ensure that heat is prevented from reaching the building interior in the first place. The most effective protection is thus external shading. If there are no external blinds, then solar protectors should be installed behind windows. In this case it is advisable to use curtains or roller blinds made of opaque, highly reflective material.

Proper ventilation is vital in cases where it is impossible to prevent rooms from heating up. Here one particularly effective measure is to throw open all windows at night. Even if there is no perceptible breeze, cooler air will still flow into the flat and reduce excess heat. This is especially important when, during long hot spells, the indoor temperatures steadily rise day by day. Of course, it is not always possible to keep windows open at night because of noise or the risk of burglary in ground-floor flats. In this case, the project team recommends that windows and doors be opened as long as possible, at least in the cooler evening hours and in the early morning. This will help to cool down the heat-storing walls, floors and ceilings of the flat.

Moreover, good ventilation of living spaces is also a proven way to reduce the risk of contracting the coronavirus: regular air exchange reduces the airborne virus load in the interior. In this way, measures to alleviate summer heat can kill two birds with one stone.

Original Publications
Schünemann, Christoph; Olfert, Alfred; Schiela, David; Gruhler, Karin; Ortlepp, Regine: Mitigation and adaptation in multifamily housing: overheating and climate justice. In: Buildings and Cities 1 (2020) 1, S. 36-55.

Project on heat adaptation in cities
(Heat-resilient urban and district development in cities – Resident-oriented knowledge generation and implementation in Dresden and Erfurt):
The project HeatResilientCity (German: Hitzeangepasste Stadt) is funded by the Federal Ministry of Education and Research (BMBF) as part of the initiative “Future City” in the research field “climate resilience through action in cities and regions”. Running from autumn 2017 to early 2021, the project budget is around 2.5 million euros. The scientific partners are the Leibniz Institute of Ecological Urban and Regional Development (project management), the Institute for Urban Research, Planning and Communication (ISP) at the University of Applied Sciences in Erfurt, the Institute for Hydrology and Meteorology at the Technical University of Dresden as well as the Dresden University of Applied Sciences. Practice partners are the Environmental Agency of Dresden, the Environmental and Nature Conservation Agency of Erfurt and the Eisenbahner Housing Association of Dresden.

Contact at the Leibniz Institute of Ecological Urban and Regional Development (IOER)

Dr.-Ing. Regine Ortlepp
Dr. Janneke Westermann

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