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Make the house fit for the climate

Climate change is becoming noticeable. Storm, heavy rain, hail or heat are already causing considerable damage to property every year. Experts say that the weather extremes will increase in the future. A thought that worries many homeowners.


A web application from the Federal Institute for Building, Urban and Spatial Research (BBSR) now offers owners the free opportunity to determine how well their house is protected against extreme weather and which structural measures can reduce risks and possible damage. The figures show that there is great interest in this topic: the web application went online at the beginning of the year and already had more than half a million hits in the first quarter of 2020.

The tool was created as part of a BBSR project with the awkward name "GIS-ImmoRisk - Development of a geographic information system for nationwide risk assessment of future climate impacts for real estate". For this purpose, the BBSR has brought an interdisciplinary development team (the Institute for Real Estate Economics IIÖ and the Agriculture, Forestry and Water Management Data Center LFRZ) on board.

There was also an advisory board accompanying the project with partners from science and practice, some of whom were also data providers, including the German Weather Service, the Karlsruhe Institute of Technology (KIT), the Association of the German Insurance Industry, Deutsche Rück, the Climate Service Center Germany and the Leibniz Institute for Economic Spatial Development. The project manager at BBSR is Ute Birk, who explains GIS-ImmoRisk natural hazards in an interview.

GIS stands for geographic information system. Can you briefly explain that to us?
Geographical information systems make it possible to bring technical data and spatial information into connection with one another and to generate evaluations on various issues. With GIS-ImmoRisk Natural Hazards, we ask about the expected damage or the risk from natural hazards to buildings.

Who are you targeting with your application?
Of course, we kept an eye on all those who have an interest in getting a better basis for making decisions about their investments and adaptation measures. The application is therefore aimed at property owners, prospective buyers and project developers.

Which factors determine the risk for a building?
The risk or the expected damage to a property from extreme weather depends on three factors: the risk at its location, its vulnerability and the value determined for a restoration of the property or parts of the property.

Properties are exposed to different hazards depending on their location or exposure, because the intensity and frequency of the extreme weather such as storms or heavy rain are not the same across Germany. This can be seen very well on the hazard maps in the tool. The factor of vulnerability to extreme weather is determined by building-related properties; the condition of the roof cladding or waterproofing, for example, is a very important parameter when it comes to resistance to moisture damage. And finally, the expected damage to a property, measured according to the new value to be determined of parts of the building or the entire building, is a factor for restoration in the event of damage.

How precise can the "predictions" be? What are they doing and what are they not?
The tool is designed as an orientation aid and provides information before seeking professional advice. It does not provide any reports.

In the GIS-ImmoRisk Natural Hazards, users can receive an assessment of current and future hazards per natural hazard for each location in Germany. In addition, owners can have the expected extent of damage for their house determined as a financial or qualitative risk. The result is the risk profile. In addition, a lot of background information is stored on the portal.

The probability of damage occurring cannot be precisely predicted. All results in the GIS tool have a certain degree of uncertainty, which is indicated in the risk profile by a speedometer symbol. An info text explains to the user why it can only be an estimate. For the expected damage, we have shown the range from the minimum to the maximum extreme value in addition to the average value.

Let's go through a specific example. A house on a slope in a region that has been hit by heavy rain several times in recent years. How do you assess the risk, which structural measures are recommended?
The tool should be used to find out the respective risk, because, as I said, the risk is not only dependent on the hazard at the location, but also on the condition of the property - in this case on the vulnerability to heavy rain - and the restoration value to be determined.

Nevertheless, it can be said that the hillside location may require special measures with a view to landslide hazards in the area and moisture damage to the building, depending on the nature of the ground and the condition of the house. In addition, the load-bearing capacity of the subsurface can be impaired. In order to get in-depth advice on the specific adaptation measures, you should turn to experts.

Making residential buildings fit for climate impacts - do you see the owners alone as having a responsibility?
Climate change is a task for society as a whole, which must be borne by all federal levels and also by civil society. In this respect, I also see politics as a responsibility. This includes, among other things, gaining new knowledge for practice through research and providing information bases and support tools such as our application.

In addition, important decisions taken at regional and municipal level can minimize the threats posed by climate change. For example, reducing the number of sealed areas enables the ground to absorb the mass of precipitation in the event of a heavy rain event, thus reducing the risk of flooding caused by heavy rain.

Another problem is the urban heat island effect on hot summer days, which determines the local climate through development and emissions in the cities. The average air temperatures there can be up to 10 Kelvin higher than in the surrounding area. Trees, green spaces, bodies of water and unobstructed cold air corridors help to improve the microclimate in neighborhoods and to reduce the negative effects of the urban climate on people and buildings.
Further individual adaptation measures on the houses themselves, such as shading systems, can also minimize the heat input into the interior.

GIS-ImmoRisk natural hazards at www.gisimmorisknaturgefahren.de
BBSR project page of the research project with research report and user brochure as downloads at www.bbsr.bund.de