HydroSKIN: Smart building facades provide protection from flooding and heat

Roads became rivers, cellars flooded: In recent weeks, massive rainfall and flooding in Germany have caused devastating damage amounting to billions of euros. An invention from the University of Stuttgart could prevent such devastation in the future: HydroSKIN, a revolutionary façade technology from the Collaborative Research Center “Adaptive Shells and Structures for the Built Environment of the Future” could protect buildings and cities worldwide against heavy rain and heat. The project was nominated as one of 20 finalists for the Federal Environment Agency's “Blue Compass” 2024 competition. 

The lightweight facade elements made of several layers of textiles and membranes absorb rainwater. This relieves the drainage system and prevents flooding. On hot days, the textile façade is moistened with water and thus cools the building and urban space sustainably through evaporation without air conditioning. Thanks to their low weight, the façade elements can be easily installed on new and existing buildings - and in a variety of designs. The textiles are even 100 percent recyclable and made from PET bottle waste.

Since 2022, researchers at the University of Stuttgart have been investigating how façades behave in heavy rain and extreme heat. "The HydroSKIN façade can absorb more than twice as much rainwater as a roof of the same size on the same building," explains Christina Eisenbarth, who invented and developed HydroSKIN during her doctoral thesis at the Institute for Lightweight Structures and Conceptual Design. “This helps to reduce the so-called surface runoff - rainwater that runs directly into the drainage system from asphalt and concrete surfaces and causes flooding when the absorption capacity is exceeded - by as much as 54 percent. And that is if only a quarter of a building facade is fitted with HydroSKIN.”

The “excess water” is directed from the facade into the building interior, where it can be used for the washing machine, toilet flushing and plant irrigation, for example. This could save up to 46 percent fresh water in a residential building. “HydroSKIN is therefore more than just a facade  - it makes an active contribution to environmental protection and resource conservation in our cities,” says Prof. Lucio Blandini, Head of the Institute for Lightweight Structures and Conceptual Design and Deputy Spokesperson of the Collaborative Research Center (CRC) 1244.

On hot days, the HydroSKIN facade acts like a cool compress for a fever: HydroSKIN cools buildings and the urban space by utilizing natural evaporation processes. While normal building surfaces can reach temperatures of over 90 °C under the scorching summer sun, HydroSKIN reduces the surface temperature to as low as 17 °C. A single square meter of this facade can completely offset the heating of 1.8 square meters of concrete or 1.4 square meters of asphalt. 

"Imagine if this system was widely implemented, the red, glowing hot spots on a thermal imaging map of our cities would suddenly turn blue-green and cool again, all without losing precious urban building land," explains Eisenbarth. The cooling capacity of the facade is impressive: 5.7 square meters of HydroSKIN cool as much as an air conditioning system  - which also saves energy costs.

“We are working tirelessly to implement this promising technology into construction practices as quickly as possible, aiming to better prepare our built environment for future heavy rainfall events,” says Eisenbarth. "HydroSKIN has been part of the start-up portfolio at the Technologie-Transfer-Initiative GmbH of the University of Stuttgart for over a year, and we are highly motivated to implement our first projects."

"Two floors featuring the HydroSKIN façade will be constructed on the D1244 demonstrator high-rise this year, to show how conventional facades can be retrofitted with lightweight HydroSKIN elements and showcasing the resulting architectural potential," explains Dr. Walter Haase, an aerospace engineer involved in the project and Managing Director of the CRC 1244 at the University of Stuttgart.

Research into the technology will continue in parallel. "In our Collaborative Research Center, we aim to thoroughly investigate the global applicability of HydroSKIN technology across various climate zones and its interaction with various existing buildings in the future," says Prof. Oliver Sawodny, Head of the Institute of System Dynamics and spokesperson for the Collaborative Research Center 1244.

The project was among the 20 finalists in the Federal Environment Agency's “Blue Compass” 2024 competition. "HydroSKIN - Building facade elements that protect against flooding and heat" came 8th place.