Improving Visual Comfort through Integrated Design in Architectural Education: A Performance Metrics Analysis of Adaptive Kinetic Facades
Maria Matheou
Profil Orcid et Marios C. Phocas
Profil Orcid 
Publié en ligne: 10 mai 2025
Pages: 63 - 74
Reçu: 04 oct. 2024
Accepté: 13 janv. 2025
DOI: https://doi.org/10.2478/acee-2025-0005
Mots clés
© 2025 Maria Matheou et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
Viewed as a response to climate change, the urgency of reducing buildings’ operational and carbon emissions is steadily increasing with the overarching goal of reducing the building sector’s ecological carbon footprint. A zero-energy building prioritises energy savings in heating, air conditioning, artificial lighting and ventilation, and often utilising renewable energy sources. Key concepts such as climate adaptation, resilient and efficient building design are vital towards zero-emission buildings [1]. In this framework, the facade plays a pivotal role in the long-term energy efficiency and resilience of buildings. Hence, conventional building facades are designed to offer only one static design solution, and a static facade cannot ensure high performance over time. Specifically, in moderate climates, it is essential to allow solar penetration in winter and reduce heat gains in summer [2].
Along with reducing the building’s total energy consumption, building façades provide vital functions for occupants' health and comfort such as lighting, energy gain, protection from sun, glare, humidity, wind, noise and fire, visual contact and safety [3]. Nowadays, it has become essential to ensure high standards of occupants’ health and comfort in indoor environments (especially in the workplace). To achieve high levels of Indoor Environmental Quality (IEQ) based on human perception, four basic environmental factors are considered: visual, thermal and acoustic comfort, and indoor air quality [4]. This paper focuses on visual comfort including illuminance, daylight availability, glare protection and view contact [5] through adaptive kinetic facades (AKFs).
AKFs optimally serve users’ evolving needs and changing external climate conditions throughout the year and day. Flexible components within building facades play a crucial role in mitigating excessive heat gain during summer months and minimising heat losses during winter, thereby effectively adapt to changing solar altitudes, optimise shading and maximize natural daylight utilisation [6]. Beyond this, AKFs introduce an aesthetic dimension to architectural design while accommodating evolving user needs and thereby ensuring an adaptive indoor experience [7, 8].
Various researchers and designers have developed numerous shading systems to improve building energy performance, prevent glare and increase daylight availability. Commonly used systems include mechanised Venetian blinds, louvres, overhangs and perforated screens such as mashrabiyas. Antoni Gaudi, Eileen Gray, Jean Prouvé and Buckminster Fuller already implemented concepts of flexibility and functionality into facades (Fig. 1). In 1890, Antoni Gaudi designed a mechanism to adjust the slats, allowing more natural light to penetrate when needed at Palau Güell in Barcelona in Spain. Later, during modernism, Eileen Gray in collaboration with Jean Badovici patented the “paravent” window, an operable folding window assembled between an inner and outer layer of shutters stating that “a window without a shutter is like an eye without an eyelid” [9]. Under this umbrella of brise-soleil, Jean Prouvé designed in collaboration with Atelier LWD, lightweight, adjustable façade panels (sun shutters) for the mass-produced schools in Cameroun in 1964 and the school complex in Béziers in 1965 [10, 11]. Buckminster Fuller, a pioneer in automated climate-adaptive envelopes, envisioned sunshades controlled by a computer program that adjust their configuration relative to the sun for the skin of the United States pavilion’s geodesic dome. The sunshades blocked sun’s rays to prevent overheating and glare or allowed them to penetrate for passive heat gain and daylighting [12].
a) Palau Güell, Gaudi, 1890 (Source: Author) b) Paravent window, Eileen Gray, 1926 (Source: Eileen Gray) c) Sun shutter, Jean Prouvé, 1964 (Source: Galerie Patrick Seguin) d) Biosphere, Buckminster Fuller, 1967 (Source: M. J. Gorman)
Kinetic facade modules have been successfully implemented in contemporary buildings such as the Al Bahar Towers (UAE), CH2 (Australia) and Q1 Headquarters (Germany). For example, the kinetic timber louvres installed on the western facade of CH2 fully shade the building while reducing solar heat gain by tracking the sun’s position [13]. Shading systems that adjust themselves according to the time of day and season can improve energy efficiency in office buildings by blocking solar heat gain and avoiding overheating. The materials used in shading systems have also been studied for their reflectivity and impact on indoor glare and artificial lighting energy requirements. Pilot projects of exterior shading, proper solar orientation, and dynamic solar control can result in energy savings of up to 60 % for lighting and 20 % for cooling [14]. Installation of dynamic solar shading systems is estimated to save up to 30 % of cooling energy and 14 % of heating energy, resulting in a reduction of carbon emissions by 22 % [15].
Despite the progress made, there are still gaps and challenges in AKF design. For instance, scientific research on solar harvesting has mainly focused on developing automatic control strategies rather than covering human comfort objectives and energy altogether [16]. Hence, integrated automated control that caters to occupants’ preferences, such as providing access to natural light and a view of the outside, tends to result in greater satisfaction and productivity. Occupant-facade interaction and the occupants’ perception of comfort are important elements of automated shading control, while residents and their behaviour influence 50 % of the energy used in a house [17]. To tackle this challenge, we present our students’ projects addressing multi-functional AKFs using performance-based architectural design. This design process enables architecture students to conceptualise adaptive scenarios for balancing functions such as solar protection, solar harvesting, indoor and outdoor comfort, and occupant preferences.
This architectural design studio aims to introduce the students to design thinking as a key pedagogical method to find innovative solutions for complex challenges using simulations and physical models. Based on the example of three case studies, as part of the design studio “Smart Shade” at the University of Stuttgart, this paper showcases how the integration of AKF design can enhance visual comfort while aligning with broader design objectives. Students were given a kinetic façade typology developed in ongoing research for a daylighting simulation exercise [18]. The next step involved conducting a comparative daylighting analysis of static and kinetic facades using an office model with a south orientation in ClimateStudio [19]. The south façade has a width of 10 m and the west façade has a width of 6 m and a height of 3 m. The case studies employ a set of performance metrics to assess the impact of AKF on various aspects of visual comfort. Key metrics include illuminance, daylight availability, protection against glare and view to the outside. By examining these metrics collectively, the pedagogical approach aims to achieve a nuanced understanding of how AKF positively impact visual comfort by dynamically responding to external environmental conditions and evolving user needs [20]. The evaluation process involved verifying multiple criteria following the standards EN 17037 [21] with additional reference to the Daylighting Handbooks I and II [22, 23].
Based on the knowledge gained from the previous exercise, the final assignment was to design and prototype a façade incorporating kinetic features. While developing a prototype, students were encouraged to investigate various mechanical components such as actuators, gears, levers and springs. By employing a small number of actuators to prevent additional weight on the facade and to ensure low energy consumption in kinematics, the operational efficiency of the kinetic system was further improved. Three different actuation methods have been used in the case studies presented, including cable-driven, self-locking gear mechanisms and snapping-induced motion. The adaptive nature of these facades enables real-time adjustments, ensuring that lighting conditions align with the diverse activities within interior spaces. Therefore, students were asked to develop scenarios of adaptivity along with user needs.
Design and performance are essential domains in creating sustainable and resilient architecture of AKF following an interdisciplinary research approach and integrated design [24, 25]. By delving into the exploration of morphology, kinematics, user-control and prototyping, as illustrated in Figure 2, initial studies on adaptive scenarios, daylighting and mechanical schemes are essential to feed the design. Following an integrated architectural design approach with lightweight construction principles, this paper emphasises the importance of synthesising morphology, kinematics and construction while optimising AKF’s functionality and daylighting performance.
Integrated design of AKFs (Source: Author, University of Stuttgart)
The design of Sun-wings was investigated through architectural concepts, kinematics, embedded actuation, and materialisation with a focus on perceiving the façade as an adaptive interface for indoor and outdoor environments inspired by retroreflector devices. The architectural design phase was a fundamental stage that specified climate adaptation scenarios, façade module sizes, arrangement, depth and materiality. Initial daylighting simulation studies were conducted to determine morphology, geometrical adaptive configurations and the associated kinematics for visual comfort. At the preliminary stage, students explored various geometries, starting with simple rectangular shapes and progressing to foldable trapezoids. The purpose was to assess their effectiveness in redirecting solar radiation. Following this, the students proceeded to compare different sizes, depths, and angles to optimise the shapes further. Students analysed parameters including illuminance, glare, daylight availability and view while redirecting incoming solar radiation. Further exploration was based on a raytracing analysis of three different shapes: flat square configuration, flat rhomboid with adjustment to sun’s angle and folded rhomboid with adjustment to sun’s azimuth.
Illuminance simulation results comparing a glazed façade are illustrated in Figure 3, which shows the modules’ reconfiguration scheme at 12 pm and 3 pm during the summer and winter solstice, respectively. Figure 4 presents a comprehensive analysis of several key performance metrics, including illuminance levels, daylight availability, quality of views, spatial disturbing glare and radiance rendering. These metrics were evaluated for a typical summer day on June 21st at 12 pm providing insights into the facade’s performance in balancing natural light and solar control. At the same time, Sun-wings satisfy daylight availability while preventing directing incoming solar radiation to the urban canyon. The results indicate that sun-wings, using a white high-reflectance textile material, reduce unwanted solar gains with 1 % disturbing glare on an annual basis. Considering the complexity introduced by the office room's south and west-facing elevations, the Pawel Walter and Elias Vanhee team explored various facade configurations to optimise the balance between solar protection and maintaining exterior views for each orientation. This approach can be observed in the indoor visualisation in Figure 5.
Illuminance simulation results and modules’ reconfiguration scheme (Source: Pavel Walter and Elias Vanhee, University of Stuttgart, 2023)
a) Illuminance, b) daylight availability, c) view analysis, d) spatial disturbing glare e) radiance rendering for June 21st at 12 pm (Source: Pavel Walter and Elias Vanhee, University of Stuttgart, 2023)
Indoor visualisation with Sun-wings (Source: Pavel Walter and Elias Vanhee, University of Stuttgart, 2023)
The Sun-wings’ modules feature two elastic folded triangular surfaces with a bar of variable length in the middle. Two parallel cables are connected to the nodes of the large edge (Fig. 6). By pulling the front cable, the modules can be adjusted to track the solar altitude. Similarly, adjusting both the front and back cables, allows the modules to align with the solar azimuth angle. A cable-driven actuation method is employed to ensure technical simplicity with minimal actuators. The cable system serves a dual function, providing stability and facilitating actuation. To minimise the number of the actuators in half, actuators on the top of the façade have been replaced with springs as they can passively push the steel wire ropes upwards when not actively pulled down by the actuator (Fig. 7). Moreover, two columns of the façade modules are clustered to share the same actuator at the bottom, while maintaining the same configuration. In this case, Sun-wings offer a vertical zoning reconfiguration. By employing a small number of actuators to prevent additional weight on the facade and to ensure low energy consumption in kinematics, the operational efficiency of the kinetic system was further improved.
Prototype of the “Sun-wings” design project in scale 1:5 (Source: Pavel Walter and Elias Vanhee, University of Stuttgart, 2023)
Actuation concept of “Sun-wings” front and side view (Source: Pavel Walter and Elias Vanhee, University of Stuttgart, 2023)
In this design project, the students Xenia Troschina and Seline Sacher aimed to incorporate solar energy generation, solar protection and user control into the classical awning system. Following the retractable principle of the awnings, the students further developed the awnings’ mechanism by dividing the system into four independently controlled panels. To allow flexibility when adapting to different functions, one part, consisting of a photovoltaic panel, rotates according to the sun's position, while the other parts are controlled by the occupants' preferences or blocking solar radiation. Different scenarios of adaptivity, as illustrated in Figure 8, have been explored by the students during the conceptual architectural phase. This includes accommodating to evolving occupant needs for privacy and view of the outside while also allowing for the non-uniform reconfiguration of the façade modules and blackout when presentations or other events occur. Besides occupant needs, horizontal zoning with different patterns on each façade side has been proposed by the students to improve indoor daylighting performance (Fig. 9).
Scenarios of adaptivity following user preferences (Source: Xenia Troschina and Seline Sacher, University of Stuttgart, 2023)
Horizontal configurations in south and west façade (Source: Xenia Troschina and Seline Sacher, University of Stuttgart, 2023)
While investigating adaptive indoor scenarios to elevate occupants’ well-being and comfort, students analysed four different shapes: rectangular, rhomboid, square hexagon, vertically and horizontally elongated hexagon. Results showed that 3.5% disturbing glare occurs during the year with the rectangular shape, which is lower than the required 5%. When the awnings protect the indoor environment from solar radiation, indoor illuminance is 750 lux for 96.10% of the daylight hours, meaning that the room satisfies the target illuminance for at least 50% of the area (Fig. 10). As shown in Figure 10, the students assessed the façade system in two different configurations when closed and open, aligning their goals with concepts of adaptivity while aiming to balance direct and diffuse light along the façade’s height. Besides this, the façade system offers high flexibility and can be blacked out when necessary. During the winter solstice, the AKF allows adequate daylight.
Illuminance simulation results in summer and winter solstice (Source: Xenia Troschina and Seline Sacher, University of Stuttgart, 2023)
Coupled with the daylighting analysis, the students calculated the electricity consumption for an office room of 155 m2 and proposed an estimated electricity yield of 3206 kWh, which is double the amount needed when photovoltaic panels are installed in every panel of the south and west façades. By harnessing solar energy, the building can effectively reduce its energy consumption, resulting in cost savings and contributing to a more sustainable energy model. The use of a bright white colour not only optimises energy generation, but also aesthetically enhances the building design (Fig. 11).
Visualization from indoor and outdoor view (Source: Xenia Troschina and Seline Sacher, University of Stuttgart, 2023)
Achieving dual functionality in this façade system was quite challenging due to the increased number of components, including motors. To overcome this complexity, the students developed a mechanically driven solution to minimise the number of actuators and mechanical components integrated into the façade modules in scale 1:2 (Fig. 12). With its self-locking mechanism, photovoltaic panels rotate independently from the other panels with the same actuator connected to a shaft. To transmit the motion from the shafts to the pivot point of the panels, the rotary motion gets converted to a linear movement and back to a rotary motion. For prototyping reasons, the students utilised 3D-printed mechanical gears with irreversible locks sharing a motor in simplifying the system (Fig. 13).
Prototype in 1:2 scale (Source: Xenia Troschina and Seline Sacher, University of Stuttgart, 2023)
3D printing, mechanical components and assembly (Source: Xenia Troschina and Seline Sacher, University of Stuttgart, 2023)
In the pleated façade modules case study, an existing project the “Snapping Façade” [26] has been further developed. The students Ursula Schaub and Petimat Bibulatova aimed at ensuring optimal daylight and view access while engaging users in a fun, dynamic interaction with the AKF. Initially, the module was applied to the reference office building and a parametric daylighting simulation analysis was conducted to evaluate its daylighting performance. The students compared three different module sizes (1.2 × 3 m, 1.0 × 2.6 m and 0.8 × 2 m), with clear and printed ETFE, a linear zebra pattern with a combination of translucent and transparent surfaces, and a horizontal and vertical module array pattern (Fig. 14). Larger module sizes, transparent ETFE with light transmission of 98% and vertical module array pattern were excluded from the next architectural design phase because they did not improve daylighting performance. After analysing the simulation results, the students improved the system’s daylighting performance by changing the module array pattern from a polar (initial design by Song et al.) to a linear configuration, allowing it to respond to the solar altitude in both, its open and closed states.
Illuminance simulation results in summer and winter solstice (Source: Ursula Schaub and Petimat Bibulatova, University of Stuttgart, 2023)
As illustrated in Figure 15, the students conducted a detailed analysis of various façade configurations for each side of the office room in order to block solar radiation while allowing access to views. This analysis was particularly focused on critical time, such as during the summer solstice at 12 pm and 3 pm. At these times, the position of the sun significantly influences which areas of the façade need more protection. The upper zone of the façade proved to be most crucial for shielding the interior from excessive solar radiation on the south side. For instance, at 12 pm, the west side is fully open since the sun is positioned mainly on the south-facing side of the building, allowing the west side to maintain clear views and diffuse light. However, as the day progresses and the sun moves towards the west, the design strategies shift accordingly to ensure solar radiation is effectively managed without compromising the quality of the indoor environment.
Illuminance simulation results and configuration set up (Source: Ursula Schaub and Petimat Bibulatova, University of Stuttgart, 2023)
Utilising the elasticity of lamellas while employing the “snapping-induced motion”, the façade module reconfigures its shape from an open to a closed configuration. By controlling the two endpoints of the lower chord of the pleated façade modules (Fig. 16) with a servo motor, the snapping deformation is achieved with minimal effort. Additionally, by upgrading the material from traditional Korean paper, which was more suitable for indoor use, to ETFE and printed ETFE, the students developed a 1:2 prototype suitable for outdoor installation (Fig. 17).
Pleated façade module (Source: Ursula Schaub and Petimat Bibulatova, University of Stuttgart, 2023)
Prototype in scale 1:5 (Source: Ursula Schaub and Petimat Bibulatova, University of Stuttgart, 2023)
In exploring innovative approaches to AKFs, three student projects demonstrated unique actuation methods addressing specific aspects of functionality and design integration. The decision-making process in architectural designs involving multi-criteria, particularly in AKFs, necessitates a careful balance between technical performance and user-centric considerations. As highlighted in this paper, factors such as indoor and outdoor comfort, kinetic mechanism (analogy of actuators to façade modules), control flexibility and solar harvesting play a pivotal role in evaluating these systems. Acknowledging the limitations of automatic control strategies, which often disregard user preferences, this design approach aims to embed actuation within the primary façade elements to reduce complexity and enhance adaptability. A comparative evaluation of the three architectural designs is shown in Table 1.
Comparative evaluation of the three architectural designs
| Evaluation Criteria | Sun-wings: cable-driven actuation method | Awnings: self-locking gear mechanism | Pleated façade modules: snapping-induced motion |
|---|---|---|---|
| Indoor Comfort: Visual | + | + | + |
| Outdoor Comfort: Rays Redirection | + | − | − |
| Kinetic mechanism: Modules/Actuator | 12/2 | 6/1 | 4/1 |
| Control flexibility | + | + | + |
| Energy generation | 0 | 3206 kWh | 0 |
The Sun-wings project employed a cable-driven actuation method to control 12 façade modules using only two actuators while maintaining a lightweight and flexible system. Furthermore, the design aims to balance solar protection with user needs by treating the façade as a dynamic interface that mediates between indoor and outdoor environments. However, solar harvesting was not considered in this study. In contrast, the Awnings project incorporated a self-locking gear mechanism, prioritizing visual comfort, user preferences and solar harvesting. This highly flexible and innovative system allows solar panels to adjust independently from other panels to protect the indoor environment from solar radiation. Nevertheless, the weight of the panels may necessitate stronger or more actuators. Therefore, further study on panel materials is important when selecting the appropriate actuators. Lastly, the Pleated façade modules project employed snapping-induced motion, leveraging material properties to achieve dynamic transformations with minimal mechanical complexity. However, this system arrayed horizontally can complicate the transition of forces; a polar array could potentially address this issue. This project focused primarily on the kinetic mechanism and visual comfort, while further studies on solar harvesting or outdoor comfort have not been addressed.
Our primary focus was visual comfort, all projects analysed and improved daylighting performance. However, when integrating solar harvesting or outdoor comfort and adaptivity, the nature of the study becomes perplexing. Technically, the students investigated why a shading system has to change throughout the date and across different seasons. The next key question was what configurations are necessary for this adaptation and what type of kinetic mechanism could support this. We followed a cyclical learning process, initially exploring the difference between a static and an adaptive shading system through daylighting simulations. After conceptually developing the motion type for each season and time of day, students fabricated prototypes to investigate the kinetic mechanisms of their project [27]. In the next phase, each group focused on optimizing the numbers of the actuators needed.
The performance-based design framework for AKFs was demonstrated through three different case studies: Sun-wings, Awnings and Pleated façade modules. Our primary objective was to explore innovative solutions for complex challenges, leveraging advanced research on AKFs, to achieve both environmental and social benefits through multifunctional facades. Along this process, evaluation criteria for both indoor and outdoor environments were quantified and assessed. One significant limitation in architectural design is the applicability of AKFs and their impact on reducing carbon and operational emissions [28]. For instance, Al Bahr Towers improve building’s energy performance, but 50 % of the occupants are dissatisfied, because they cannot control or interact with the adaptive façade [29].
In this design studio, we examined the potential of balancing solar protection, solar harvesting and user interaction in façade designs. By integrating these three key elements, we aimed to create facades that do not only meet daylighting performance goals but also enhance user experience and comfort. This is particularly crucial as occupant satisfaction plays a critical role in the success of adaptive systems and automation. In conclusion, AKFs offer significant potential to integrate solar harvesting systems and enhance solar protection while addressing broader challenges such as mitigating urban heat island effects, reducing energy consumption and fostering user interaction. By aligning these objectives, AKFs can transform the built environment into more sustainable, adaptive and human-centred spaces. Our future research will focus on this holistic approach that balances occupants’ well-being, daylighting performance and preferences with energy performance.