Dusseldorf A house made entirely from recycled materials: This is how it is in Hanover in the Kronsberg district. Sauna benches, crown caps and old farm doors are built in here. “It’s a lifestyle. The materials have a life story, ”said architect and expert for sustainable building Thomas Kraubitz, commenting on the advantages of the idea.
Recycling is still a niche in the construction of residential buildings. The project in Hanover is more of a beacon than a pilot project for the client. But the rapidly rising raw material prices in construction could now give the idea a new boost.
Because while construction prices are rising in Germany, large quantities of demolished buildings are still ending up in landfills. Raw materials are one of the price drivers in construction. But how interesting is the concept for building owners? Below is an overview.
The idea behind the concept is just as impressive – as it is complicated in practice. If a building is no longer needed and consequently demolished, the materials are made recyclable as much as possible. That is, they are taken out and sorted. One tries to bring the raw material back to its original form as well as possible.
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For years, science has been striving to better exploit this potential. Terms such as urban mining, circular economy or cradle-to-cradle all more or less describe the hope that the built-in raw materials can be returned to the construction cycle after demolition.
Construction industry causes a lot of CO2 emissions
Because the environment in particular would benefit from the concept. In 2020, around 38 percent of global CO2 emissions could be traced back to the construction industry. Record levels, as a UN report found. The Paris climate protection agreement could benefit from more recycling in construction.
As early as October 2018, the Federal Ministry of the Interior, Building and Home Affairs made it clear that the construction industry should broaden its perspective in the direction of sustainable building materials. According to a publication, old components have “still untapped potential” in the commercial sector. In 2020, Berlin also decided on a third resource efficiency program designed to ensure that raw materials are used more sparingly.
In practice, however, the industry sometimes struggles with this. The majority of construction waste is still not reused in the same way. Old clinker walls are particularly good. They usually consist of just one material. Concrete can also be recycled. After the demolition, it is crushed and later used in civil engineering, for example on roads.
This can in principle have advantages for building owners. Because raw material prices continue to rise. The price index of the Federal Institute for Geosciences and Natural Resources (BGR) climbed from 846.30 euros in August 2020 to 1462.90 euros in July 2021.
“The use of recycled building materials brings price stability and thus additional security,” says Kraubitz. However, the construction company Gundlach, which built the recycling house in Hanover, admits that a high proportion of recycling is more expensive. However, the company believes that price neutrality could be achieved should the trend reach broader segments.
A concept that requires a lot of planning work
However, building owners have to be patient: building according to the cycle concept involves a lot of planning work. The future property owners have to deal with problems that do not arise in a conventional new building with new building materials.
For example, materials that were previously used elsewhere cannot simply be removed and recycled. Rather, it needs experts to assess the materials. The quality of the building materials plays a major role here. Pollutant assessors often have to make an assessment beforehand. They take a close look at the purity of the material and assess whether it can be used again.
Sustainability expert Kraubitz says that adhesions are a particular problem. The raw materials are not easy to solve, so recycling would be too costly. Pollutants such as asbestos still play a major role today.
Consequently, it must also be clarified who is responsible for damage after such building materials have been used. According to Kraubitz, this responsibility should lie with the builder or the expert who assesses the building materials. Because used components are also a risk for craftsmen, because they usually do not accept any warranty for parts that have already been installed.
Another problem is the building area. If you want to use recycled materials, you have to calculate how much you want to build with them. Since the materials are not yet fully established on the market, the supply is limited. For example, if you want to build a house from old, recycled clinker bricks, you have to assume that you will have to use new building materials or alternative solutions.
There is another obstacle with it. Demolition companies are already coming up with the idea of separating materials according to type and offering them recycled. But the market is still too small, demand is low and there is a lack of storage space for these materials. This can be a problem, especially in large cities, where a lot of construction and demolition is going on, as Kraubitz explains.
Individual start-ups have recognized the topic and have already set up “swap sites” for old building materials. You coordinate the communication between the demolition and the new building. But in Hanover, too, the company had to say goodbye to its goal of completing a 100 percent recycling house. In the end, more than half of the building materials used had already been used.
First examples all over Germany
The concept is still gaining popularity. A high-rise quartet called “Four” is being built in Frankfurt, which also follows the principle of the circular economy. On the RWE site in Essen, too, the planners have made it their task to reduce the use of new building materials. In Hamburg, in the middle of the Hafencity, there will also be a project like this from next year – Moringa. The materials are plugged and screwed instead of glued. And the walls must not be glued or painted with paint.
The upheaval could be worthwhile for the builders in the long term. Because the German Society for Sustainable Building (DGNB) sees a clear problem, according to spokesman Felix Jansen: It is currently unclear who is responsible for the disposal of construction waste after a demolition. If the DGNB has its way, the builders could be held responsible for this in the future. And this could also change attitudes towards avoidable demolition waste.
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