Extreme heat and severe flooding events are transforming innercity areas into 'urban heat islands' and 'pluvial flood basins': While rising population and urbanization growth coincide with a virtually unlimited surface sealing and the construction of 'high and higher-rise' buildings, the impacts of a changing climate force a permeabilization of vulnerable urban structures. A significant leverage effect for climate adaptation can be attributed to the building envelopes of tall buildings. Due to their high percentage of urban surface coverage, they provide significant transformative potential for climate activating and regulating the urban rainwater and temperature management.

Hydroactive skins represent a novel, integral approach to enhance urban climate resilience effectively and economically without occupying additional ground surface. As 'artificial lightweight retention surfaces' based on textiles and foils, hydroactive skins absorb the wind-driven rainwater hitting the building façade, which considerably reduces the load on sewerage infrastructure. The majority of rainwater hitting the façade surfaces is kept from contamination by soil pollution thereby facilitating its utilization inside the building to reduce the building's internal fresh water and energy consumption. In hot spells, water is released by the hydroactive skins through evaporation to (re-)create the natural and sustainable cooling effect. The implementation of textiles implies besides their specific functional advantages a minimal weight per unit area of the facade, which results in addition to significant savings in mass, grey energy and CO2 emissions, in a universal applicability of hydroactive skins in new as well as in existing buildings.

The proposed lecture presents the technological and material-specific fundamentals for an enhanced comprehension of hydroactive skins. It outlines the operating principles of façade-integrated evaporative cooling and rainwater absorption, and, based on comprehensive experimental analyses, it discusses the multiple design and development parameters that are decisive for the functional design of multilayer textile- and film-based hydroactive skins.