So far, the quarter of the future has only been available in computer animations. The sun is shining, people are leisurely strolling through car-free streets, the trees are green and the houses are made of wood. The first preparations will start this year, and by 2027 the first apartments will be ready for occupancy little by little: the Schumacher Quarter, built on the site of the former Berlin Tegel Airport. 5000 housing units. The largest timber construction quarter in Europe, if not in the world. “What can emerge there,” says Raoul Bunschoten, “is a new aesthetic of cities.” And on top of that one that stores more greenhouse gases than it causes during construction.
Bunschoten, Professor of Sustainable Urban Planning and Urban Development at the Technical University of Berlin, is currently working on a kind of wooden construction kit for the new quarter. Pieces that can be easily assembled into buildings, and whenever possible from the surrounding forests. Procurement, production, all logistics – it’s a complex thing. “But if we succeed, then we’ll turn cities into huge carbon stores,” says Bunschoten. Conversely, the country should think twice about whether it really wants to build 400,000 new homes in the conventional way. “We shouldn’t build primarily with concrete,” says the architect.
Climate sinner buildings
But that is exactly what has been the rule so far. A good year ago, the Federal Institute for Research on Building, Urban Affairs and Spatial Development calculated the ecological footprint that a building leaves behind over the years. The numbers were gigantic. In 2014, a third of Germany’s greenhouse gas emissions were caused by buildings. The lion’s share was made up by the operation of the buildings, i.e. the energy requirements for heating and hot water. But a quarter was spent on the construction phase.
The cement literally weighs particularly heavily. If one ton of it is produced, 600 kilograms of carbon dioxide are produced. With renewable energies and no matter how much efficiency, you can only do something here to a limited extent – because the largest part is produced during the deacidification of the limestone, a chemical process. Manufacturers like Heidelberg Cement are therefore toying with the idea of capturing and storing CO₂ underground. The quantities are considerable: Eight percent of all emissions worldwide can be traced back to cement production.
In addition, there are large amounts of steel and plastics in many houses, a sixth of all emissions from house construction can be traced back to this; plus of course the energy consumption around the construction site. The more fossil electricity there is in the grid, the worse the balance here. And then demolition and disposal of the rubble are not included in most balance sheets. Even the sturdiest building will have them eventually. After all, the new coalition is now planning a “digital building resource pass” – it could not only make more transparent what’s in a building, but also help with recycling. When demolishing later, the different building materials could be separated more easily.
But there are differences. As a rule, there are fewer emissions in brick walls than in cast ones. And of course the footprint per inhabitant is smaller the more residential units a building has. From a purely energetic point of view, the single-family house is a greater burden than an apartment building, which is of course not a very popular thing to hear in a country with more than 16 million single-family houses. And other environmental impacts, such as the sealing of surfaces, are distributed among more people in apartment buildings. And more commuter traffic usually goes hand in hand with new settlements on the outskirts of cities.
Residential construction also influences the regional climate
Of course, not only the world climate is affected by all this, but also the regional one. New apartments in the cities also mean greater densification and often greater expansion. “And that has urban climate effects,” says Andreas Vetter, who deals with such issues at the Federal Environment Agency. Fresh air corridors could disappear, or important green spaces. The cities could warm up even more. “You have to keep that in mind during construction.” Green facades or roofs could help to dampen such effects.
This kind of green can also be found in the models of the Berlin Schumacher district. Of course, there is still a lot to learn about building with wood, admits urban planner Bunschoten, and there are also challenges, for example with taller buildings. “But you shouldn’t pretend that building 400,000 homes a year just with cement would be without consequences either.” And anyone who knows old half-timbered houses knows about the qualities of wood as a building material.