-Evaluation of the effect of kinematic axes and the geometric model of the kinetic facade on providing natural lighting in an office building in Tehran

Background and objectives: Kinetic façades represent a dynamic design approach that integrates movement to adapt to environmental conditions the concept of motion as a design input. One of the strategies of this facade is to control the light entering the interior. Fixed or dynamic horizontal shades are the best choice for south orientation, while vertical shades are usually used in east and west directions. Studies have shown that horizontal shading is more efficient than vertical shading. Indoor lighting conditions can affect the occupants’ visual comfort, satisfaction, thermal comfort, health, mood, motivation, performance, and productivity. Literature indicates that geometric and movement models play a role in controlling daylight and glare, although less attention has been given to movement axes in four directions. Also, it is unclear what kind of movement axis is appropriate for each façade direction. This research aims to utilize natural lighting using geometric models and rotational motion axes of the kinetic facade in the north, south, west, and east facades of an office building in Tehran. The novelty of this article is in examining the motion axes of the kinetic facade in response to Tehran's climate. For this purpose, the rotational motion axes in three horizontal, vertical, and diagonal modes in four directions have been measured to create optimal light in the interior space. The selection of samples is based on constructed examples that have not been used in previous studies, and the focus of this research is more on rotation motion axes and two geometric models, circle and rectangle.
Methods:This study utilises an applied, quantitative research methodology and is quantitative in nature. Using the simulation tool, the rotational motion axes of the kinetic facade are analyzed and evaluated in four directions, considering both circular and rectangular geometric models, and in relation to daylight in an office building in Tehran. Rhino software version 6.32, Grasshopper plugin and Honeybee Plus plugin version 0.0.06, and Ladybug version 1.5.0 were used for simulation. The Python programming language has also been used to calculate averages. The first step is to simulate the movement of the sun with the Ladybug plugin according to the weather file of Tehran. In the next step, a sample office room with an open plan, measuring 4 m in width, 6 m in length, and 3 m in height, accommodating six employees, was evaluated according to the dynamic daylight indicators. The room had a window-to-wall ratio of 90% of the facade without shades. In the next step, the existing two geometric modes of the kinetic facade, circle and rectangle, have been measured and compared according to the rotational movement axes (horizontal, vertical, and diagonal) in four facade directions. Then, according to the responsiveness of the facade to natural lighting, the most optimal geometric model and movement axes based on angle and dimensions (length, width, and radius) are suggested for all four directions of an office building in Tehran.
Results and conclusion :Recent research on kinetic facades in Iran and around the world indicates that kinetic facades are more responsive than fixed types in reducing glare and controlling daylight. Among them, geometric models, kinematic modes, movement axes, geometric model dimensions, room dimensions, the opening and closing angle of the geometric model of the facade in relation to the location of the sun, and the climate of the region play a significant role in optimising natural lighting in the interior space. According to the glare index (ASE) findings, the north facade does not require a shade, as the interior space receives sufficient daylight without one. Therefore, natural lighting simulation analysis with a kinetic facade has been done only for three directions of the south, east, and west facades. According to the simulation results, the two indicators, ASE and UDI, are of special importance. This is because when the shade opening or angle is half-closed, less light enters the space. As the percentage of useful light index decreases below 500 lux, the interior space may receive less than 500 lux of useful daylight at its far end.
Additionally, when the aperture or angle of view is open, more light enters the interior space and the amount of glare (ASE) shows values above 10%, which means that indoor glare and visual discomfort may occur. Therefore, optimising these two indicators is necessary to receive useful daylight in the interior. In the next step, the values of the two indices ASE, UDI less and DGP were averaged using the Python programming language. The simulation results show that the geometrical models of rectangle and circle with a rotating movement model with the horizontal axis at the top in the south, west, and east walls and with the diagonal axis at the top, both geometrical models in the east and west facade of an office building in Tehran are appropriate for providing optimal dynamic daylight indices. After comparing the geometric models based on the ASE and UDI indices in three directions, it is evident that the rectangular geometric model with a rotating movement model on horizontal and diagonal axes outperforms the circle geometric model with a rotating movement model on horizontal and diagonal axes. Also, the most suitable rotational motion axes of the kinetic facade for the two western and eastern facades are the horizontal and diagonal axis at the top and for the southern facade the horizontal axis at the top. Among the limitations of this research is the lack of an office building built with a kinetic facade in the field, so that a comparison can be made between the simulated results and field measurements.
On the other hand, natural lighting measurement devices in the indoor environment have limitations and cannot simultaneously measure the amount of daylight and glare in the indoor environment. In future research, it is possible to evaluate the kinetic facade with a rectangular geometric model and rotational movement model with horizontal and diagonal axes in four directions of the facade based on the amount of energy consumption, visual comfort, and thermal comfort using simulation or field observations. Furthermore, this facade can be studied in different climates and cities to determine its use with a geometric model and a proportional movement model in each city, according to the internal daylight. The results of this research can be applied to similar climates outside of Iran.