Acta Polytechnica CTU Proceedings https://doi.org/10.14311/APP.2022.38.0375 Acta Polytechnica CTU Proceedings 38:375–381, 2022 © 2022 The Author(s). Licensed under a CC-BY 4.0 licence Published by the Czech Technical University in Prague SOLAR SHELTER: EXPLORING ARCHITECTURAL DESIGN INPUT FOR INDUSTRIALLY-CRAFTED SHADING DEVICES Ulrich J. Ponta,∗, Sigrun Swobodab, Peter Schoberc a TU Wien, Institute of Architectural Science, Department of Building Physics and Building Ecology, Karlsplatz 13, A-1040 Vienna, Austria b TU Wien, Institute of Architectural Science, Department of Digital Architecture and Planning, Karlsplatz 13, A-1040 Vienna, Austria c Austrian Forest Products Research Society (HFA-ÖGH), Franz-Grill-Straße 7 A-1030 Vienna, Austria ∗ corresponding author: ulrich.pont@tuwien.ac.at Abstract. European Cities are strongly affected by the Urban Heat Island effect and Climate change impacts in recent and future summer periods. As such, the integration of passive cooling strategies is of increasing importance for the overall AEC (Architecture-Engineering-Construction) domain. Amongst other strategies, one of the most prominent strategies is the timely deployment of shading devices. While the shading device constructions connected to the inside, interstitial position or exterior of transparent building envelope components is thus an important part of the building, little change can be observed in the principal design and technology of such shading elements. Moreover, target conflicts between shading device deployment and architectural appearance can be observed in European Cities. For instance, the ensemble protection of the Vienna City morphology was – for a long time – considered to be more important than potent shading devices. The present contribution presents the approach of an effort toward highly-esthetical, functional shading devices that provide – despite their architectural-design approach – a high degree of shading performance. Together with the window-building industry, four different shading device designs have been designed, developed and virtually tested. The design process was guided by critical reviews by domain experts and performance simulation efforts. We present the genesis of the four designs and their performance implications as a proof of concept that effective shading systems can be understood as part of the esthetics of a building and practical passive cooling device at the same time. Keywords: Shading devices, summer overheating, passive cooling strategies, industry-university collaboration, urban heat islands, climate change, cooling demand reduction. 1. Introduction Summer overheating has become a prominent topic in recent years, which can be seen by the rising num- ber of scientific research, publications, and the action plans of different cities and regions to react to sum- mer overheating. Once specific topics reached the attention of governments, regularly it can be assumed that the issue is not any longer just an academic one. While the analysis of the impact of CO2 emissions on global temperatures can be traced back to the 19th century [1], the information of the general public of rising temperatures is a matter of the second half of the 20th century [2–5]. Moreover, most people – by feeling – would say they did not identify the en- vironmental issue of rising temperatures as a severe one before the millennium change to the 21st century. Other environmental issues, however, were a matter of public interest and also international action was taken against these issues: This is true for the hole in the ozone layer [6, 7], and on the forest dieback phenomena [8]. Both matters were identified to be ma- jorly caused by emission of certain harmful substances that reacted with atmospheric components to acid or diluting substances. In contrast to the mentioned environmental threats, climate change and urban heat island effects has rather seldomly popped up in the public perception. One of the first occurrences might have been the summer heat wave of Central Europe in 2003, which showed the high vulnerability of ur- ban citizens against overheating, in detail for people who themselves are part of vulnerable groups due to their age, health situation, or social status [9]. Stud- ies and reports reckoned that the heat wave caused up to 70 000 people’s death [10]. It might be clear that fighting global warming by de-carbonization is somehow a half-lost battle, even if politicians proudly announce successes such as the Paris treaty [11], and its different follow up international treaties. While the concepts and ideas for reducing emissions, decarboni- sation of industry, economy, and society are discussed and memoranda of understanding are signed and de- clared as path guide by decision makers, the reality is different and still shows rising CO2 emissions [12] and thus a clear and present risk of reaching tipping points which would inevitably move mankind and nature into a hot-house earth scenario [13]. Urban citizens are stricken not only by the climate change itself, but also 375 https://doi.org/10.14311/APP.2022.38.0375 https://creativecommons.org/licenses/by/4.0/ https://www.cvut.cz/en U. Pont, S. Swoboda, P. Schober Acta Polytechnica CTU Proceedings by the so called Urban Heat Island effect. This term describes the observation, that urban agglomerations tend to show higher temperatures and also acceler- ated heating up in heat waves, which is widely due to reduced vegetation, use of materials of low albedo and high energy storing potential, and – a major aspect – anthropogenic heat emissions by buildings, traffic, and systems. Between 2011 and 2014, a central European research project was conducted by a large consor- tium, which intended to identify sources and extent of the urban heat islands in European Metropolitan Regions [14], and – moreover – to develop strategies in mitigation [15]. Mitigation refers to minimizing the UHI effect as such by specific urban interventions, such as a balanced ratio of buildings and greenery, implementing greenery in building facades and roofs, minimizing unnecessary heat emissions, and utilizing the benefits of deployed green-blue infrastructure. If mitigation also refers to minimizing the harmful ef- fects of heat waves, urban heat islands, and climate change onto citizens, the scale of interventions can be described as from “general city master planning” to “small scale impacts at the individual residential unit”. The recently published guidebook on cooling of cities edited by the UN [16] clearly defines passive cooling strategies such as adapted design of the buildings regarding orientation, morphology and ratio of trans- parent components, careful operation of the buildings, and education of the occupants as key elements in fighting overheating. Needless to say, architects play a key role in implementation of such passive cooling strategies. Previous studies, however, identified that while the selection of appropriate building materials for summer overheating protection is of importance, it is by far outnumbered by the impact of the occu- pants’ behaviour regarding shading deployment and ventilation [17, 18]. While ventilation via windows can be considered as easy-to-implement passive strat- egy, effective night-time cooling might require semi- automated windows that employ a ventilation-only position and automated opening and closing, as for instance suggested in [19]. Shading devices can be fixed or moveable/deployable. As of today, many ar- chitects consider shading device implementation as a severe aesthetical issue for new building designs, but also for adaptation of the existing building stock. This has – in part – to do with the rather “functional” design of deployable shading devices. While architects often dream of performance-oriented architecture far away from today’s built practice (compare [20, 21]), a close-by industry designing of shading devices rarely can be found in academia or in the architectural prac- tices of today. The authors and the window- and shading-device building industry therefore decided to ask graduate students of architecture to rethink today’s available shading devices. The present con- tribution presents the methodology and the results of these efforts and shall thereby act as a proof that solar shading can be aesthetically pleasing and highly performative at the same time on the one hand, and on the other hand as a showcase of the reached design solutions. 2. Methodology The overall efforts were conducted within a 5 ects De- sign Studio for graduate students of architecture. The task was to develop non-of-the shelf shading devices for both existing, richly-decorated Gründerzeit-Buildings as can be found in many European Cities, and new (generic buildings). Thereby, both design, function- ality and performance impact was set for in-depth explorations during the design studio. Naturally, ar- chitects are not full-fledged engineers, but generalists and designers. As such, the students were supported by three instructors of architectural and building con- struction engineering background. Moreover, during the semester, three review sessions with experts from the window- and shading-construction industries were held, which allowed the students to receive a SWOT (strengths-weakness-opportunities-threats) analysis of their concepts and inspiration and guidance for the further development. Beyond the design and construc- tion integration, the participating students were asked to consider the aspects of kinematics and performance impact. While the kinematics required animation or at least “thumb cinema” illutstrations that show the state of the system in any state during the operation, the performance impact on the summer overheating of buildings was emulated via the generation of virtual buildings that employed the corresponding design and a thermal building performance simulation via the simulation process described in the Austrian Stan- dard for summer overheating [22]. These simulation efforts were conducted with the software Archiphysik in version 17 [23]. Students were asked to generate presentations for the Austrian community of window constructing companies (Plattform Fenster), which evaluated the projects and acknowledged the principle necessity of rethinking shading devices. 3. Results and Discussion In this section the four different designs are presented briefly, including their potential application domain (new windows / new buildings or building stock / existing windows), and performance impact. Thereby advantages and potential challenges are highlighted as well. 3.1. Project 1: Rutatus-Blende (“Rutatus – shutters”) The defined aims of this design were as follows: (i) integration in window-retroffiting efforts, (ii) development of a Casement window upgrading kit, (iii) compatible in aesthetics to traditional Grün- derzeit facades, 376 vol. 38/2022 Solar shelter: Exploring architectural design input . . . Figure 1. Project 1: Rutatus-Blende: Upper left: functional principle, Lower left: Façade view be integration in a Gründerzeit façade, sequence on the right: Shading effect / sun penetration reduction (rendering). (iv) inexpensiveness in investment and operation (maintainance). Given these goals, some design decisions could be made, such as the positioning of the shading device at the outside of the window plane, the manual op- eration (no motorization), and a specific identity in the design. The final design was inspired by claws grid systems, which for a very long time have been used as anti-burglary devices in front of doors and windows. While this systematic in its traditional form never was intended as a “shading device”, the key further development of the project was to find possi- bilities of attaching fabric that does not hamper the kinematic of the system but unfolds for cutting short of sun penetration and glare. Figure 1 illustrates the Rutatus-Blende principles. The strong part of this project is for sure in its easy to implement concept as a frame that can simply be set into the window niche. The aesthetical impact on Gründerzeit facades might be an acceptable one, in comparison to traditional jalousies. Moreover, the shading device can be deployed independently from the state of the window as opened or closed (given that we have turn windows opening to the inside). This means that sun shading and ventilation would in principle be possible at the same time. An integration in the interstitial space of casement windows can be considered. However, some shortcomings of the de- sign need to be mentioned as well: The shading device is – due to its frame limitation – not useable to fully darken a room, some “open” spots remain. Depending on the used canvas simulations showed reductions of 21 to 79 % of transmitted short wave radiation. As a result the amplitude of indoor temperature curves over 24 hours can be significantly lowered, if the shad- ing device is deployed during daytime in summer heat waves. 377 U. Pont, S. Swoboda, P. Schober Acta Polytechnica CTU Proceedings Figure 2. Project 2: Whirlshade: Upper Row: Installation and opening sequence; Lower Row left: Box with mechanics (pulleys, motorization); Lower Row right: principle construction of the foldable sail. 3.2. Project 2: Whirlshade This concept – illustrated in Figure 2 – was inspired by the folding principles used for solar panels of satellites and space-faring vehicles. Utilizing a box structure that can be mounted in line with additional insula- tion material on the outer perimeter of existing and new buildings’ walls close to the window, the wings of the shading system can be transformed from hid- den to visible, to partly deployed and fully deployed. This step-wise deployment allows gradients of light penetration to the inside but also full shading. Needless to say, the system of Whirlshade offers a high degree of innovation and can – if applied ac- cordingly – also provide a “sense-of-wonder” aesthetics, as for instance the Façade of Jean Nouvels’ Centre Du Monde Arabe [24]. However, it shares also the shortcomings, which are a potential high degree of maintenance and thus connected cost and effort. One might argue that different deployable membrane-based shading devices also have a certain degree of complex- ity, as such the design would require a further technical fine-detailing to allow for a concluding evaluation of its usability. Regarding the summer heating mitigation the system – if deployed at the right time with the right extent – provides full relief of summer overheat- ing for typical residential rooms. Similar to project one, the deployment of the system is independent of the opening state of the window behind. 3.3. Project 3: Sonnensterne (“sun and stars”) This concept has been developed based on innovation pertaining to “translucent” timber [25, 26]. This ma- terial can be generated by removing major parts of the lignine structure from the wood. The material provides slow bio-degradability (such as any other tim- ber element), and as such will change over time. The design of the shading devices utilizing this material is based on vertical construction axis, which can be moved from a hidden position of the left and right perimeter of the window niche to central positions via a railing system. Along these axis a set of rotation points in provided, which – in the basic version have one “part” of the star visible. Similar to the concept of the solar flower [27], different parts of the system can be deployed via rotation around the central rota- tion points. As such gradients of shading are possible. Different levels of overlap also form different light and radiative penetration barriers, allowing users to adopt their degree of shading accordingly. Figure 3 illustrates the principles of the Sonnensterne-System. Advantages of the system include – similar to the other projects – the independence from the window open/closed state, the flexibility of the system regard- ing degree of shading on the one hand and the appli- cation possibilities on the other side: The system can also be used as an alternative to photochrome or elec- trochrome glass panes used for generating privacy at still transmitting light in a translucent fashion. Such application could be used in fully glazed conference 378 vol. 38/2022 Solar shelter: Exploring architectural design input . . . Figure 3. Project 3: Sonnensterne: Upper rows: Sequenze of different states of deployment; Lower Row: Isometry and horizontal section of the technical principle of Sonnensterne. rooms. Similar to the other projects, simulations conducted in the framework of the development proofed that summer overheating could be significantly reduced by deployment of the Sonnensterne system. Disadvan- tages of the system encompass the complex kinematics, even if this was reduced to “sliding” and “rotating”, and potentially the sensitivity against wind pressure events, as the system is foreseen to be outside of the buildings and window niche perimeter. 3.4. Project 4: Fenster-Krausen (“window neck brace”) This project is inspired by the historic neck braces worn by noble(wo)men of earlier centuries. This idea has been translated into a folding system that can be used as alternative to traditional deployable jalousies. Similar to them, the degree of lowering and the posi- tion of the individual elements can be changed. How- ever, the relative position of the single blinds is not just rotated but can be folded / unfolded to the neighbour- ing blinds. As a result the shading structure of this project provides a lively, irregularly pattern, compara- ble with the leaves of a tree and their diffusing effect on light and radiative transmission. Performance-wise, the system is as capable as regular deployable blinds. Challenges connected with this system include the rather complex fabric-pull-rope relation in the differ- ent parts of the shades. Figure 4 illustrates the system schematically, as well as the gradients of shading pos- sible. 4. Conclusion The present contribution showcased four different inno- vative and non-of-the-shelf shading device ideas. Two of them – Fenster-Krausen and Rutatus-Blende – seem to be widely adaptable in the sensible building stock of Gründerzeit-Buildings without shock-changing the overall appearance of such facades. Given the neces- sity to provide sun shading also for these buildings, such ideas should be followed up more in detail. The two other projects – Sonnensterne and Whirlshade – are rather ambitious and innovative in their kinematic patterns but seem to be better suited for new build- ings. All of the designs were examined towards their lighting and shading impact. Whereas performative aspects in both domains could be satisfactorily full- filed, open questions, such as potentially disturbing light/shadow patterns in the inside remain a matter to be worked upon. While this contribution on the one hand highlighted the early design phases of such shading devices, it highlighted that architectural de- signers can contribute to the mitigation of overheating also in a creative fashion, not only by purchasing and implementing the industrial products by now. On the other hand, the industry acknowledged the ne- cessity to supplement the current offer of shading devices by high-performantive, aesthetically satisfying 379 U. Pont, S. Swoboda, P. Schober Acta Polytechnica CTU Proceedings Figure 4. Project 4: Fenster-Krausen: Left: Façade view, middle and right, upper row: Fully closed system, middle and right, lower row: Nature-inspired light / radiation transmission. and contemporary technology using shading possibili- ties. Future research shall emphasize the collaboration between the industry and academia to intensify the knowledge exchange and thus allow to realize shading devices close to the presented ones of this contribution. 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