Refurbishment: Insulate and heat old buildings in a climate-friendly manner


If you want to understand the problems of the energy transition, you shouldn’t look around in chic new districts, but in residential areas like the “Kuckuck” on the outskirts of Hamelin. Yellow-plastered rental blocks from the 1930s are lined up here, many of them rather dilapidated. A typical development, as it was built all over Germany up to the 1960s – and which still makes up a large part of the housing stock today.

Quarters like this are a sore point in the energy transition. According to the German Energy Agency (dena), heat in buildings in Germany accounts for around 35 percent of total final energy consumption. In order for Germany to achieve its climate targets, around 1.5 to 2.8 percent of the existing stock would have to be renovated every year, depending on the scenario. But currently it is only around one percent. Because while in new buildings or luxury renovations it is comparatively easy to install everything that modern building technology can offer, in older residential complexes the difficulties accumulate: the building fabric is often full of surprises, the ownership structure is complicated, the financial leeway is limited – after all, after the renovation, too there is still enough affordable housing left.

The experts basically agree on the priorities for the renovation: first the insulation, then the heating. “A passive house standard can only be achieved in exceptional cases when it comes to renovations, but you usually come close,” says Rainer Pfluger from the Institute for Construction and Materials Science at the University of Innsbruck. And if the heating requirements of an apartment decrease, the heating can be correspondingly smaller and more economical. According to Pfluger, however, the industry would like to skip this first step in order to earn more money with more powerful heat pumps.

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