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Conditions for local adaption of building policies in German cities according to their building structure and demography

Panel: 3. Local action

This is a peer-reviewed paper.

Authors:
Judit Kockat, Buildings Performance Institute Europe, Germany
Clemens Rohde, Fraunhofer ISI

Abstract

Both, building's properties and the demographic growth of major German cities affect the energy demand and the local effort needed to achieve long-term climate protection targets. On one hand, population growth increases the demand for residential units and the energy demand may rise. On the other hand, prices for living space increase in growing cities. Therefore, people are willing to satisfy with less living space, which may reduce the energy demand. In this paper, we analyse both of these factors to inquire how the energy demand is changed by migration. How much energy is still needed to be saved and what does that cost? The answers provide for political action on energetic retrofit to be adapted to the local migration trend.

In our approach, German cities are clustered with regard to their age, size and attachment. Therefore, we use the algorithms proclus and k-means with a principle component analysis. Based on the clusters, we calculate the energy savings, assuming constant specific savings for similar buildings derived from bottom-up simulations. Finally, we amend the potential of the clusters based on their future growth, so as to assess that demographic influence.

The biggest and most robust cluster is formed by eight main eastern German cites. Not surprisingly, the separation of the country has left significant traces within architecture and age distribution, which are both energy relevant properties. We found that most of the migration related impact can be directly linked to the population growth. However, about 10 % to 22 % of the impact is caused by a change the building structure. This means, that not every city can achieve the same energy savings. Without counteraction, this effect is largely diminished by a rebound effect, since low housing prices in shrinking cities cause people to afford more living space.

Due to the different modernization in the cities, the precise effects of migration are to be assessed individually. However, this study quantifies the impacts of migration and the change in use intensity on energy demand, savings and investments. Thereby, it also reveals starting points for local adaption of policies to demographic growth.

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