Transformable tensile façade : performance assessment on energy, solar and daylighting

Abstract

Building facade plays an important role in the overall building design. Its exclusive aesthetic appearance represents the unique DNA that the designer encodes for each building. Moreover, it significantly impacts the energy consumption of the building throughout its lifecycle. This is where the research recognizes the potential of tensile membrane facade (TMF) systems to marry geometric complexity with improved building performance. However, several obstacles exist which impede designers attempting to incorporate tensile membrane structure (TMS) system into their design. One of the fundamental problems this research explores is how designers can gauge the impact of incorporating TMF into their design despite the increased complexity in geometric and physical properties TMF add to the design. The applicable tools and means and methods to enable this process have rarely been discussed and identified in the prior research. To address these issues, this research first reviews current efforts on facade and shading strategies to improve various aspects of building performance, followed by an introduction to the overall research method. Next a photo-goniometric lab experiment is conducted to obtain the test sample's optical properties. This experiment is followed by two case-based experiments to understand the impact of the optical property input in conjunction with the impact of different shading strategies. The impact of a transformable TMF system is also explored through a series comparative studies. Finally, this research presents the limitation and discusses future work in the conclusion. Through the goniometric lab testing, the measured optical properties shows a slight difference from the theoretically derived results. This high resolution measurement might have a significant impact on the lighting and energy simulation performance. However, due to the limitation of the current energy simulation tools, the full Bidirectional Scattering Distribution Function (BSDF) cannot be considered and therefore the actual impact cannot be obtained at this current research stage. As a result of the low resolution intake of the energy simulation tool, only 7 angular optical values were taken into consideration during the energy simulation process. The first case-based experiment focuses on assessing the impact of external textile shades on solar heat gain and energy consumption including the consideration of the textile shade's optical property. There were a total of 6 shading scenarios tested in three different climate zones. Based on current simulation results, although the performance variation can be observed, the impact of the transmission (Ts) value might not be significant enough to affect the design decision making process. However, current research only tested on flat shading surfaces and excluded the potential of electrical lighting energy reduction, the actual impact of using optical properties cannot be accurately gauged based on the current results. Furthermore, the potential of textile shades to provide higher daylighting performance has yet to be considered. As a result, the incorporation of the goniometric measured Ts value or higher resolutions Ts value during the simulation process is still a research in question that is worth further exploration. When comparing different shading strategies, the results demonstrate that the control mechanism of the fabric shade has a significant impact on the performance. While the research only explored the fabric shading strategies as a flat system with one solar heat gain threshold control mechanism, the significance of the impact can already be observed. This implies higher potential with the incorporation of the dynamic system control along with the angular variation of the shading surface. The second case-based experiment focuses on assessing the impact of a transformable tensile membrane facade system on daylighting performance. The experiment utilized a shoe-box model with four different membrane layer configurations. The results demonstrated that the system can provide nearly consistent daylighting performance throughout different times and dates if the facade's geometric variation is possible. While this study only applies a specific performing criteria on a shoebox model as an example, more substantial opportunities can be foreseen that the adaptive membrane facade system is able to accommodate occupants- needs for different occupancy zones during different times, dates and orientations. In addition, the use of the adaptive membrane facade enables appearance variation with assorted possible configurations which can broaden designers-design space with fixable and inspirational yet high performing components. This not only encourages designers to be more creative regarding the facade system but also promotes performance based design. While there are several unknowns and questions that still need to be further explored, the experiments support the vision of the research.