A comparative study of the kinetic movement pattern of a triangular geometric facade regarding natural lighting in an office building in Tehran

Since the reception of natural lighting in different places is different regarding the sun path and the different sky conditions during the day, season, and year, employing a kinetic facade allows for the adjustment and enhancement of interior natural lighting levels. The geometric pattern and the movement pattern are critical issues in the design of kinetic facades. One of the strategies use in this facade is the control of light entering the space. Another advantage of their efficacy in enhancing the quality of daylight is the improvement in visual quality, particularly in office and public areas. Hence, this present study explores natural lighting by employing two kinetic facades. These facades feature a comparable triangular geometric model but differ in their non-symmetrical folding and rotating kinetic design on the south wall of an office building in Tehran. Consequently, the dissimilarities in kinetic models are compared based on the utilization of natural lighting, and their similarities are identified and analyzed to determine the most suitable option.

To assess natural lighting, the quantitative method and simulation tools utilized were Grasshopper and Honeybee Plus plugin version 06, along with Ladybug lbt version 1.5.0. Subsequently, the simulation results were scrutinized employing the comparative study method. Initially, the simulation involves defining the geometry of a room with specific dimensions: a width of 4 meters, a length of 6 meters, and a height of 3 meters, resulting in a total area of 24 square meters, intended for four employees. The simulated model is located in Tehran, with no shading obstacles. The facades will open and close with the position of the sun and the perpendicular vector on the triangular geometric model. The simulation is run for three days of the year: the 21st of March (spring equinox), the 21st of June (summer solstice), and the 21st of December (winter solstice) (due to the similarity of the autumn equinox with the spring equinox, the latter is not considered) and working hour is from 8 a.m. to 4 p.m.

When comparing the facades, it is observed that the folding kinetic model presents a potential issue of glare and visual discomfort in the space during the months of June, March, and April. This concern is particularly notable at 12 noon in both June and March, coinciding with low light conditions in the space. However, the facade with a rotating kinetic model is only faced with the issue of insufficient light in the space. In order to address these issues, various parameters have been modified. To enhance UDI (Useful Daylight Illuminance) indices with a rotational kinetic model, adjustments were made to ASE (Annual Sunlight Exposure), sDA (Spatial Daylight Autonomy), and UDI indicators with a folding motion model. Variable parameters included alterations in facade size, modifications to the visual transmission coefficient of glass, adjustments to the reflection coefficient of interior walls (ceiling and wall), and changes in the angle or degree of openness for these indicators.

In conclusion, it can be said that a kinetic facade with a triangular geometric pattern and asynchronous motion patterns exhibit different performances in response to natural lighting, considering daylight performance indicators. The facade with a rotating pattern demonstrates a notable impact on the UDI (Useful Daylight Illuminance) daylight indicator, and this effect can be mitigated by adjusting the angle. However, in the kinetic facade, the fluctuation of ASE (Annual Sunlight Exposure) and UDI (Useful Daylight Illuminance) indicators is less influenced. This is attributed not only to the shifting position of the sun in relation to the facade but also to the simultaneous necessity of altering both the extent of the facade opening and the reflection coefficient of the window and glass. The response of both facades, influenced by the variable parameters, places greater emphasis on the degree of facade opening and its correlation with the sun’s position, rather than on the reflection coefficient of the surfaces and the visual transmission coefficient of the glass. Finally, the rotational motion pattern performs better in response to natural lighting.