Textile Façade for Mitigating Urban Heat and Pluvial Flooding
HydroSKIN represents a revolution in façades: The lightweight, textile skin absorbs wind-driven rainwater hitting the façade. Its use inside the building reduces water and energy consumption. During hot season, HydroSKIN releases water to cool the exterior and interior environment by evaporation. The aim is to reduce urban heat and flood risks effectively and economically by activating the immense façade surface in our cities. HydroSKIN can be implemented to any new and existing building façade.
Cross-border/international
Germany
Other
Australia
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Mainly urban
It refers to a physical transformation of the built environment (hard investment)
No
No
As a representative of an organisation
Name of the organisation(s): University of Stuttgart, Institute for Lightweight Structures and Conceptual Design (ILEK) Type of organisation: University or another research institution First name of representative: Christina Last name of representative: Eisenbarth Age: 29 Please attach a copy of your national ID/residence card:
Extreme heat and heavy rainfall events with severe inundations have a significant impact on urban architecture, resulting in considerable personal injuries and material damage. Nowadays, the proportion of façade surface areas in urban environments with tall buildings is immense, thus offering a high leverage effect on climate resilience and sustainability of buildings and cities can therefore be attributed to the building envelopes.
Whereas most existing façades are designed to provide only minor qualities at a district or urban level, HydroSKIN provides a decentralised absorption of wind-driven rain hitting the building façade, its targeted use inside the building to reduce water and energy consumption as well as time-delayed release of water in heat periods to cool the interior and exterior environment by evaporation.
The core element of HydroSKIN is a so-called spacer fabric, which consists of two textile layers that are kept apart by threads and so are well ventilated. The high rate of air circulation facilitates the evaporation of water and enhances the cooling effect of the facade. On the outside, the spacer fabric is covered by a water-permeable textile layer, which allows almost all raindrops to penetrate and at the same time protects the fabric from impurities. A film on the inside drains the water into the lower thread system. From there, it can either be stored in a reservoir or, when used directly in the building, help reduce water consumption. On hot days, rainwater or even fresh water can be returned to the facade element, where it evaporates and thus provides a natural cooling effect. The lightweight system design of textiles and foils enables a wide range of applications at all new and existing building façades.
Textile Façade
Rainwater Harvesting
Evaporative Cooling
Inundation Prevention
Rainwater Management
While social developments lead to increasing urban densification, surface sealing, and the construction of high-rise buildings, the effects of climate change, such as extreme heat and heavy rainfall, require the opposite: the creation of more infiltration and buffer areas for reducing “urban heat islands” and inundation risks. Two complementary approaches to climate resilience are being pursued to protect against and respond to climate challenges: climate mitigation by reducing emissions, as well as climate adaptation for reducing or avoiding damage.
The combination of climate mitigation and adaptation strategies, by addressing both climate challenges of heat and inundation risks, is seen to have great potential for dealing with the global environmental issues in a sustainable way. In this context,
HydroSKIN represents a climate-adaptive lightweight façade element based on textiles and foils, that offers a minimal weight per unit area, thus contributing to climate mitigation by reducing the building-related mass, grey energy, and CO2 emissions on the one hand. On the other hand, HydroSKIN provides a retention surface in the façade. During heavy rainfall events accompanied by wind, the façade add-on element absorbs the wind-driven rain striking the building envelope thereby reducing the load on urban sewage infrastructure and mitigating the risk of flooding. During hot periods, the targeted time-delayed release of water via wetting and evaporating on the façade improves the urban microclimate by cooling the building skin and causing a down-flow of cold air into the urban area around the building.
The objective of HydroSKIN is to relieve the drainage infrastructure and regulate the urban microclimate with minimal technical effort, resource, and energy consumption effectively and economically but without occupying any further urban ground surfaces.
The façade significantly influences the external appearance of the building. Nowadays, innovative and aesthetic lightweight materials in the building envelope, that minimise the embodied mass, grey energy and CO2 emissions of the façade and the entire building thereby contributing to climate mitigation. HydroSKIN is a lightweight building envelope creating a unique translucent aesthetic effect with textile, haptic surface qualities that differ from all conventional facade materials, thus improving the external appearance of the building. Since HydroSKIN is made of polyester fabrics, it can not only be produced of recycled textiles - such as your old t-shirts! - but also in various colours and patterns enriching the design spectrum widely.
HydroSKIN covers buildings into a very lightweight translucent envelope, that particularly in combination with a glass façade can be fabulous. The operation of HydroSKIN during rainwater absorption as well as during water evaporation can be seen from the building inside, which is a very particular experience for its users. In addition, the translucent textile fabrics on the outside provide sun and glare protection for the inside.
HydroSKIN is a lightweight facade element to be implemented in new but also existing buildings. Due to its modular design, the lightweight HydroSKIN add-on element framed in an aluminium profile can easily be mounted to all conventional façade types such as external thermal insulation composite systems, mullion and transom facades as well as element facades to improve their climate-resilience in terms of rainwater and temperature management of the building as well as its urban environment. The retrofitting of existing facades is dedicated to the static restriction of reducing the additive loads to a minimum, as these were not taken into account in the original design of the existing construction. This construction constraint can be solved by the use of textile lightweight skins in the described sense with great design and performance scope. The use of textile- and film-based materials results in a minimum weight per unit area of the HydroSKIN of only approx. 1 kg/m² in a dry state and approx. 5 kg/m² in a water-saturated state.
HydroSKIN is based on polyester textiles, which are available in unlimited quantities all over the world and can be purchased cheaply, ensuring its applicability in all relevant climate zones. The system design can be individually adjusted to the prevailing climatic conditions. For example, in very hot dry regions, multifilaments, which are much more water absorbent than monofilaments, can preferably be used in order to extend the cooling duration and enhance the performance of the system.
The evaporative cooling potential of water-saturated textile materials textile fabrics was investigated by empirical tests that are accessible for people to discover this new façade application. Humidification of the textile resulted in an immediate temperature reduction. Under laboratory conditions of 35 °C room air temperature and 20% room air humidity, the wet textiles showed a temperature reduction at the textile surface of 8-12 Kelvin, outdoor test rig evaluations even indicated up to 15 Kelvin temperature reduction. The temperature decrease was accompanied by a coherent cool downdraft of about 0.2 to 0.4 m/s, which favours a potentially useful implementation in tall buildings for cooling the urban space below.
Using the absorbed rain water inside the building could not only cover the raw water demand for toilet flushing, plant irrigation etc. and thus reduce the total water consumption of the entire building by up to 45 %, but also lead to significant savings in water pump energy, which increase exponentially with the building height.
By integrating further building-physical or -technical components for interior air temperature control and humidification, one can obtain a multi-functional façade system. Combined with an adaptive control strategy, the use of hydroactive façades enables significantly increase of user and indoor comfort while simultaneously reducing water and energy consumption for interior conditioning.
A group-specific survey is currently being conducted in Australia to examine the acceptance of HydroSKIN among planners and industries, but also private householders, public authorities and politicians.
The development of the HydroSKIN is part of the research within the sub-project C01 "Adaptive building envelopes with climate performance" of the collaborative research centre 1244. Funded by the national German Research Foundation (DFG), the CRC1244 is evaluating the Potential of “Adaptive Skins and Structures for the built Environment of Tomorrow” thus facing the urgent issue of a responsible consumption of the available, natural resources. The aim is a radical reduction of mass, CO2 and energy in the building sector with a coherent decrease of global warming in terms of climate mitigation.
Within the framework of the CRC1244, the world’s first adaptive high-rise building, D1244, has been constructed at the University of Stuttgart Campus. Equipped with an extensive monitoring infrastructure the building serves to investigate new façade systems under real weather conditions in order to get local performance data. HydroSKIN prototypes are currently evaluated at the D1244 high-rise building. The first results indicate an even higher cooling performance then the preliminary laboratory investigations of up to 15K.
In order to also validate the HydroSKIN concept at an international level, the installation of prototypes in other climate zones is planned in future. Current cooperations with the University of Sydney aim to a prototypical installation and evaluation of HydroSKIN in the Australian more humid climate.
The Institute for Lightweight Structures and Conceptual Design (ILEK) is a pioneer with a long tradition in the fields of lightweight construction and resource-efficient architecture. Founder of the ILEK, structural engineer, architect and ground-breaking thinker, Prof. Werner Sobek supervises the Phd of Christina Eisenbarth thus enriching the project with his immense knowledge and wealth of experience in the field of façade design and engineering.
Under the leadership of the current director, Prof. Lucio Blandini, the traditions of the ILEK are being expanded with new topics in the field of digitalisation. Prof. Blandini leads the façade planning of the D1244 high-rise building and supports the implementation of the first HydroSKIN façades.
Dr.-Ing. Walter Haase is significantly involved in the technical development of the HydroSKIN. As an aerospace engineer, his skills in the fields of thermodynamics and aerodynamics are of particular importance in the calculation of driving rain yields as well as evaporation rates. His experience now flows into the development of the test facilities as well as the metrological evaluation of the rain absorption behaviour and the evaporative cooling effect.
Christina Eisenbarth already had been focusing on the development of architectural adaptation strategies to global climatic challenges during her studies. Within her research activities at the ILEK, she specialised in the design and construction of textile and foil-based façades. Combining her knowledge in both areas, Christina Eisenbarth invented HydroSKIN and initiated a research funding within the interdisciplinary research project CRC1244. The collaboration within a team of architects, civil engineers, building physical engineers, aerospace engineers, mechanical engineers, system dynamics engineers etc. is from particular benefit for the HydroSKIN façade development enriching the research with new perspectives.
Whereas most façades focus on their building-physical performance for the interior, HydroSKIN is the first façade that combines climate mitigation and adaptation strategies, whilst simultaneously addressing both global climatic challenges of urban architecture: “urban heat islands” and pluvial inundations.
The implementation of textile materials in the building skin opens up a revolutionary new spectrum of functionalities in the façade. Apart from a significant weight reduction of the entire building, the use of textiles as a retention surface in the façade enables the absorption, targeted use, and time-delayed release of precipitation water to reduce flood and heat risks. Thus, addressing the rising climatic impacts of urban architecture. “Urban heat islands” as well as floodings caused by heavy rain events will constantly increase in future with global warming as well urbanization trends by rising the number of sealed surfaces, thus requiring considerable personal and material injury.
HydroSKIN to be modularly implemented in both new and existing buildings reduces the impacts on urban sewage systems as well as heat loads by evaporative cooling of environment and building. Essential part of the HydroSKIN is an external, multi-layered 3D-textile acting as a collector and evaporator. All embedded materials are fully recyclable. Due to a “mono-material design", the individual layers even can be returned to the material cycle after use without separating them from each other. In combination with further adaptive components for interior conditioning, the use of HydroSKIN significantly increases user comfort while simultaneously reducing water, material, and energy consumption of the entire building. An automated control strategy of the HydroSKIN contributes to a resource-efficient use of the absorbed rainwater e.g., for indoor air conditioning or user consumption in the building or its surroundings with a consequent reduction in water and energy consumption.
To preliminarily investigate the cooling potential of HydroSKIN, an evaporation laboratory test stand with temperature and humidity as well as flow velocity sensors has been installed. Under climate conditions of approx. 35 °C ambient temperature and 25 - 35 % relative air humidity, various wet textile materials have been examined. After validating their evaporation performance, further experimental investigations focused on their rain absorption capacity carried out by high speed and resolution imaging. Based on the experimental evaporation and absorption results, their mechanical strength has been examined. Finally, a selection of multi-layered collector and evaporator prototypes have been developed. These HydroSKIN prototypes have been evaluated under real weather conditions at the D1244 high-rise building at the University Stuttgart Campus.
High-rise buildings are characterised by a high amount of material, energy and CO2 with no or marginal qualities for urban climate mitigation and adaptation. As Fazlur Khan already figured out with "Premium for height", the material consumption as well as the embedded amount of "grey" energy bound up in the building increases disproportionally with the building height due to the exponentially rising wind loads acting on the building façade. Due to these wind loads, the amount of rainwater hitting the building envelope also increases. In hot periods, these high wind velocities enhance the evaporative cooling performance accompanied by a cool air flow that moves downward into the urban space. Considering this potential of vertical retention and evaporation surfaces as a new “benefit for height” we assume a completely new era of climate-adaptive and climate-resilient high-rise buildings and cities. As building envelopes represent a significant part of high-rise buildings as well as of the surrounding urban surfaces, they have a major leverage effect on the urban micro-climate and sustainability of buildings and cities.
Ongoing urbanization and re-densification raise the percentage of sealed areas and increase the risk of flooding in urban areas. Sealed areas with runoff effect are connected more and more to the existing sewage infrastructure. Therefore, the hydraulic capacity of conventional sewage systems is often exceeded in case of heavy rainfall events leading to a risk of flooding with significant material damage and personal injury. The consequences range from selective overflow in road space to severe flooding of entire streets and damages to infrastructures and buildings. Re-dimensioning the existing sewage systems, if at all possible, would entail a huge amount of work and costs.
Additionally, the absorption of solar energy on sealed road and building surfaces in the city leads to a significant increase of air temperature, which will analogously rise in the future due to global warming. So-called "Urban Heat Islands" are generated that, apart from heat stress, pose a health hazard especially to older people. Both extremes - flooding and heat stress - are further amplified by climate change. According to forecasts, increased heavy rainfall events with intensities far above the prescribed rainfall limits as well as a significant temperature rise with coherent increasing number of hot days are to be expected in the future. Retention areas for decentralized infiltration of rainwater are therefore urgently required particularly in dense urban zones. Acutely needed are concepts for decentralized rainwater retention and water evaporation, which contribute effectively and economically to an improvement of urban rainwater and temperature management to be applied on building surfaces and other civil engineering structures with a minimum amount of embodied mass, energy and CO2 emissions. In this context, textile and foil based HydroSKIN elements offer an immense potential.
