One of the primary risk factors for catastrophic weather events is the high rate of roof closures in cities. Asphalt and concrete surfaces absorb incoming solar radiation and convert it into heat. In contrast to green spaces, the evaporation of water – and thus the natural regulation of the microclimate – is further restricted by closed roads and rooftops. Urban heat islands are developing.
There is not enough space for rainwater tanks and storage basins in the inner city areas. Almost all rainwater arriving in the sewer system must be drained, as high precipitation and closed areas with increased drainage effect cause the sewer system to be overloaded with a dangerous overflow.
There is an urgent need for urban areas to retain rainwater and regulate the microclimate through evaporative cooling—areas that do not take up valuable urban living space, in order to take effective and nonetheless economic action against two intensifying climate threats.
Now Christina Eisenbarth of the Institute for Lightweight Structures and Design (ILEK) at the University of Stuttgart has come up with a globally applicable solution for adapting cities to climate change. The architect developed a water front system that acts as an artificial holding area in the building envelope.
The light textile facade elements called “HydroSKIN” absorb rainwater that strikes the building structure at an angle and release the water during hot periods in order to naturally cool the interior spaces of the building through evaporation. Item size is flexible. The minimum surface weight allows for easy installation over all conventional facades in new buildings as well as in existing buildings.
The main component of HydroSKIN is the so-called spacer fabric, which are two layers of fabric that are separated by threads and are therefore well ventilated. High air circulation enhances water evaporation and increases the cooling effect of the facade. The knitted fabric is surrounded on the outside by a water-repellent textile covering that allows almost all raindrops to penetrate and at the same time protects the knitted fabric from dirt from insects and leaves. The film inside drains water to the lower side system. From there, whether it’s stored in a tank or used directly on the premises, it can reduce water consumption. On hot days, the water is returned to the facade element, where it evaporates, thus ensuring a natural cooling effect through evaporation. Not only is the interior of the building cooled, but also the surrounding areas.
Tall buildings offer special potential for hydroactive building envelopes. Not only because of its vast interface area. As the height of the building increases, rain hits the facade of the building as rain driving at an angle due to the forces of high winds, so that more rain hits the facade from the height of the building about 30 meters than it does on a horizontal roof area of the same height measured. On the other hand, higher wind speeds intensify the evaporative cooling effect, resulting in a cool air current that is drawn downward into the urban space.
Laboratory tests have been able to demonstrate that the surface temperature of the HydroSKIN interface can be lowered by approximately ten degrees through the effect of evaporative cooling. Water facade elements are now being tested under real weather conditions in the D1244 high-rise building at the University of Stuttgart: five HydroSKIN elements are installed on the tenth floor of the adaptive high-rise building, where extensive measuring devices are used to record the facade’s ability to absorb water when it rains and its ability to evaporate during hot periods.
The invention has been patented. Technologie-License-Büro (TLB) GmbH supports the University of Stuttgart in patenting and commercializing innovation. TLB is responsible for exploiting the technology.
For more information: Dr. Frank Schlotter ([email protected])
“Certified tv guru. Reader. Professional writer. Avid introvert. Extreme pop culture buff.”