Green infrastructure is now a well-established essential
Berlin, 21. February 2020
On the second day at bautec the “GRÜNBAU:TALKS | Green, resilient, sustainable” focused on the impact of climate change in urban areas. And such effects are already more noticeable than had previously been thought. At the start of this event the presenter Philipp Sattler from the DIE GRÜNE STADT foundation made the following observation: “Green infrastructure is now no longer just nice-to-have, but is a must-have”. The question is now how cities should be built in the future in order to cope with increasingly heavy rainfall as well as hotter summers.
The response from Marco Schmidt of the Federal Institute for Research into Building, Urban Affairs and Spatial Development (BBSR) was to advocate the greening of buildings and energy-efficient cooling of buildings. He presented examples of how cities can prepare for climate change. For him the key is interdisciplinary thinking and working. By means of evaporation chill, green roofs significantly reduce surface temperatures. Whereas bitumen strips on flat roofs can heat up to 60°C in summer, on a roof that has been planted with vegetation this is reduced to just 20°C. In this way green roofs not only have a cooling effect externally but also in the building below. This explains the current trend for the greening of roofs and installation of photovoltaics.
The imbalance between evaporation and the run-off of rainwater by sealing off the underlying area has an adverse effect on what is known as the small water cycle. In Berlin and Brandenburg 80 per cent of rainwater evaporates, and only 20 per cent is allowed to reach rivers, and as a consequence their water levels are reducing all the time in summer. This is a global phenomenon and is leading to the drying out of the ground all over the world. And with greater densification in urban agglomerations this sealing of the ground is on the increase. A combination of green roofs and cisterns to catch the rainwater is a way of remedying this situation. Using the Institute for Physics in Berlin Adlershof as an example, Schmidt presented a building façade that has been greened by the use of some 450 plants in tubs. This is not only better in terms of the investment costs but is also more effective than a conventional sun-screening system. Green also offers advantages with regard to operating costs: after three years the operating costs of the greened facade amounted to 1,300 euros p.a., compared with 16,500 euros for the conventional method. “Most architects still have a phobia about using plants, but this will become inevitable in the future”, says Schmidt.