System Design

HydroSKIN represents a revolutionary façade concept for rainwater harvesting and evaporative cooling. The lightweight textile skin absorbs the wind-driven rainwater hitting the building façade. The use of harvested rainwater inside the building e.g., for toilet flushing, plant irrigation and wash machine operation leads to a reduction of fresh water by up to 45 % accompanied by a significant decrease of energy consumption. In heat periods water is released by HydroSKIN to cool the interior and exterior environment by evaporation. The aim of this artificial lightweight retention surface is a drastic reduction of urban inundation and heat risks by relieving the sewage infrastructure and providing natural microclimate regulation with a minimal amount of embedded mass, energy, and CO2 emissions.

Central element of HydroSKIN is a special three-dimensional spacer fabric, two textile layers that are kept in distance by connecting pile threads providing water transport. Spacer fabrics are caracterized by a high air circulation that favours water evaporation and enhances the cooling effect of the façade. To the outside, the spacer fabric is covered by a water-permeable textile layer, that protects the inside from pollution particles and insects whilst favouring the permeation of raindrops at the same time. An optionally integrable intermediate layer enables increased water absorption and extended evaporation performance of the textile multi-layer system by means of suitable non-woven or multi-filament structures. A film on the inside drains the water into the lower profile system. ^

The multi-layer design of HydroSKIN can be individually customised to the respective climate conditions, user requirements and design guidelines. The single layers are combined into an easy dismountable and fully recyclable system that is characterized by a minimal weight per unit area of only about 1 kg/m² in dry state and 5 kg/m² in a wet state thus being adaptable to both new and existing buildings. The lightweight hydroactive building skin creates a unique translucent aesthetic effect with a textile, tactile surface texture. HydroSKIN can be offered in a large variety of design options, such as printed, coloured, illuminated, 3D-shaped or even kinematic elements, that provide different states of shade and visibility in the façade from opaque, closing, to partial shading and fully transparency.

Optical investigations of the water droplet impact behavior on textile surfaces indicated an absorption of almost the entire amount of wind-driven rain by the textile outer layer. Empirical evaluations of the cooling effect showed a temperature reduction at the textile surface of about 8-12 K, accompanied by an associated cool downdraft into the urban space below. A glass façade absorbs solar radiation and converts it into heat energy, warming a theoretical urban air volume of 14,823 m³ by 10 K per hour in terms of urban heat island effect. HydroSKIN, meanwhile, assuming an equivalent façade area, would cool a volume of 13,719 m² by 10 K per hour. Each square metre HydroSKIN consequently almost neutralises the negative impact of one square metre conventional urban building surfaces.

High‐rise buildings are characterised by a high carbon footprint with no or marginal qualities on urban microclimate. As Fazlur Khan once pointed out with „Premium for Height“, the material, energy and CO2 consumption increases significantly with the building height due to the rising wind loads acting on the façade. What if these were not seen as an obstacle but as a potential to mitigate urban heat islands and inundations? Above a building height of 29 m more wind-driven rain strikes the façade than an equal roof or ground area. Cooling capacity also increases with the wind impact on the building. Considering this potential as a new “Benefit for Height” we foresee a new era of climate‐adaptive and climate‐resilient high‐rise buildings and cities with a low carbon but climate-positive footprint.