By Sharifah Fairuz Syed Fadzil, Ali Ahmed Salem Bahdad, and Farhana Mohd Razif.
School of Housing, Building, and Planning, Universiti Sains Malaysia (USM), Penang, Malaysia.
While it is well known that light shelf can help deflect and redirect both sunlight and daylight to the deeper interiors, little is known on its behavior under real intermediate tropical sky. In many buildings, light shelf was constructed in similar ways regardless of the window orientation. In this research, by using a parametric modeling and optimization, five parameters of light shelf were studied on South orientation, in the three critical dates according to the Equinox and Solstices in the sun path. Simulation and optimization were run at selected times to see the effects to the natural illumination effects. The results were also compared the base case which was the model without any light shelf. Results were mapped to form diagrams which can be followed as usable guidelines to designers who need information on how to use the light shelf more effectively.
One of the most effective daylight devices to control sunlight entering the indoor space is a light shelf. Light shelf plays a critical function in improving and controlling interior daylight performance, expanding the occupants' visual comfort. Its performances rely upon various parameters such as geometry, materials, dimensions, the inclination angle of the external portion of the device, external climatic conditions . The challenge in the tropical climate with various sky conditions by using LS is how to make the system work dual; to provide a fully functional shading facade and lighting system that operates appropriately for all sky conditions . LS has been discussed in many studies as suitable resolution for promoting daylight in SL spaces. It is a technique that can be modified, offering a range of design solutions. It can be easily placed on the outer and/or the inner of a side aperture, it can come in varied shapes design from static flat forms to curved reflective surfaces, or it can even be actively controlled . LS can vary depending on their height, width, angle, and reflectivity, which can all be adjusted to enhance the daylighting performance of LS in response to surrounding environmental conditions such as cloud formations and altitude angles of the sun . There are a number of previous researches [3-10] on LS configuration, different methods and variables of LS, different sky conditions and criteria performances to find the best light shelves configurations. However, few studies have been performed on daylighting performance using LS with different variables design in tropics climate. Additional studies should be conducted to determine the role of light shelves as daylight guiding systems by performing experiments and simulations on such systems, especially in overcast sky condition. However, there is still a gap and a lack of guidelines to using LS in tropical climate. For example, in most previous studies, a set of optimum fixed solutions were resolved for the entire year, and this to a great extent conflicts with the atmospheric conditions of the tropics. In other words, once selected and implemented, the design variables are expected to stay unaltered, therefore, only one type of static light shelf system is not adequate to accommodate a day-to-day usage by offering optimum daylight efficiency. This research aims at developing a framework as a design guideline for optimizing LS system for designers and practitioners in the early design stage. This framework for optimization is composed of parametric design, integrated daylight simulation software, and genetic algorithms. The applicability of this optimization method is checked by the case analysis of office space and various light-shelf parameters as shown in Figure 1, Table 1 and Table 2 . The suggested of the reference office model parameters settings, materials and configurations are listed in too.
Figure 1. Reference Model
Table 1. Reference office model parameters
Table 2. light-shelf design parameters to be optimized
The approach that combines genetic algorithms and parametric simulation tools for optimization has recently become a popular method for building performance analysis. The framework of this study employs a parametric daylighting design method using Radiance which developed in Rhino/Grasshopper and Ladybug and Honeybee plug-ins. Rhino as a modelling tool, Grasshopper as a parametric interface, and Ladybug and Honeybee tools for daylight analysis application using Radiance. To assess the trend of the selected daylight acquired from the performance criteria, parametric simulations and optimization for chosen parameters have been performed at; 21st of June (June solstice), March (equinox), and December (December solstice) in the year, at four critical times of daily office work; 09:00, 12:00, 15:00 and 17:00, which are represented respectively as four different sun angular in a day. These specific dates were chosen to cover all possible circumstances of daylight exposure, which represented the most critical climate conditions of the Malaysian sky sun path. The Useful daylight illuminance (UDI) metric has recently been commonly utilized under various conditions, and it has proved effective in evaluating the daylight efficiency of an architectural room. this metric uses annual simulations to determine the percentage of daylight at a given sensor node according to an appropriate illumination level. In this research UDI was used to performance comparison of different LS parameters to optimize the best LS parameters design for office space parameters.
The optimization simulation results highlight several optimum cases of light shelf that better enhance the illuminance performance by keeping hourly illuminance levels within the accepted range for useful UDI. The optimum design parameters values of the BOC for selected times are presented in Table 3. The solutions from the optimization processes for selected dates and times marked are presented in Table 4 to Table 6. The first column shows the UDI values while the second column shows the best optimal kinetic light shelf option geometries integrated to the south facade of the office room. The last column shows the best optimized cases (BOC) of controlled kinetic light shelf geometry option, with daylight amounts dropped in the office work plan, in which UDI is changing between 0.00% and 100.00%. The blue grids are closer to 0.00%, while red grids are closer to 100.00%. The yellow grids refer to the average value of UDI, which is more or less 50.00%.
Table 3. Best parameters of optimized design
Table 4. The results of the best optimized parameters options on June
Table 5. The results of the best optimized parameters options on March
Table 6. The results of the best optimized parameters options on December
On 21st of June, March, and December, as shown in Figure 5.19 and Figure 5.20, the UDI values of the BC are 43.8%, 38.1%, and 39.4% at 9:00h. The final optimized UDI for BOC succeeded in fulfilling the required criteria of UDI by 48.1%, 53.1%, and 50.6%, which are 8.8%, 15.0%, and 6.9% slightly higher than the BC respectively. At 12:00h the UDI values of the BC are 53.8%, 35.6%, and 49.4%. The BOC achieved UDI by 53.8%, 54.4%, and 65.0%, which are 15.6%, 18.8%, and 15.6% slightly higher than the BC respectively. At 15:00h the UDI values of the BC are 38.8%, 38.8%, and 48.8%. The BOC achieved UDI by 55.6%, 55.6%, and 63.1%, which are 16.9%, 16.9%, and 14.4% slightly higher than the BC respectively. At 17:00h the UDI values of the BC are 37.5%, 36.3%, and 45.6%. The BOC achieved UDI by 49.4%, 55.6%, and 51.6%, which are 9.4%, 13.1%, and 6.3% slightly higher than the BC respectively. Figure 2 to Figure 4 presented the simulation results analysis for the cases; BC, and BOC at four different times in terms of UDI levels.
Figure 2. Simulation results analysis for the BC and BOC in June at four different times in terms of UDI levels
Figure 3. Simulation results analysis for the BC and BOC in March at four different times in terms of UDI levels
Figure 4. Simulation results analysis for the BC and BOC in December at four different times in terms of UDI levels
Some of the most critical components in the design of a light shelf is the choice of the optimum parameter to ensure optimal performance. Regardless, most previous researches assessed the relevant values using factorial design or one at a time, in optimizing the parameter. In the meantime, the use of parametric modeling and optimization by evolutionary computation has become more common nowadays to evaluate optimal solutions. An investigation study to determine the most appropriate controlled light shelf parameters for the case of daylight performance enhancement using a useful daylight illuminance indicator, in a south-facing reference office space was conducted. This is done by comparing various light shelf configurations through a parametric simulation study, using integrated parametric Rhino/Grasshopper plugins with Radiance. To test the suitability of the various configurations of light shelf for facade design, a criterion UDI 300-2000lux thresholds relating to the effectiveness of the day-lit office environment was established. This part of the research presents a parametric method that couples parametric modelling tools with Radiance daylight simulation engine and applies it to select optimal values of light shelf design parameters associated with office buildings in the tropics' climate of Malaysia to maximize useful daylight during working hours. The optimization results of the simulations focused on the illuminance performance for horizontal work plane. The comparisons of illuminance levels were conducted among the optimal parameters of the LS. The comparison of the results of best optimal light shelf options with reference model (base case) clearly showed great potential in raising the useful daylight levels in all hours.
1. Zazzini, P., et al., Experimental Analysis of the Performance of Light Shelves in Different Geometrical Configurations Through the Scale Model Approach. Journal of Daylighting, 2020. 7(1): p. 37-56.
2. Lee, E.S., et al., Market transformation opportunities for emerging dynamic facade and dimmable lighting control systems. 2004, Lawrence Berkeley National Lab.(LBNL), Berkeley, CA (United States).
3. Kontadakis, A., et al., A review of light shelf designs for daylit environments. Sustainability, 2018. 10(1): p. 71.
4. Lee, H., H.-I. Jang, and J. Seo, A preliminary study on the performance of an awning system with a built- in light shelf. Building and Environment, 2018. 131: p. 255-263.
5. Berardi, U. and H.K. Anaraki, The benefits of light shelves over the daylight illuminance in office buildings in Toronto. Indoor and Built Environment, 2018. 27(2): p. 244-262.
6. Lim, Y.-W. and M.H. Ahmad, The effects of direct sunlight on light shelf performance under tropical sky. Indoor and Built Environment, 2015. 24(6): p. 788-802.
7. Mangkuto, R.A., et al., Optimisation of daylight admission based on modifications of light shelf design parameters. Journal of Building Engineering, 2018. 18: p. 195-209.
8. Meresi, A., Evaluating daylight performance of light shelves combined with external blinds in south- facing classrooms in Athens, Greece. Energy and Buildings, 2016. 116: p. 190-205.
9. Mohapatra, B.N., M.R. Kumar, and S.K. Mandal, Positioning of light shelves to enhance daylight illuminance in office rooms. Indonesian Journal of Electrical Engineering and Computer Science, 2019. 15(1): p. 168-177.
10. Warrier, G.A. and B. Raphael, Performance evaluation of light shelves. Energy and Buildings, 2017.
140: p. 19-27.
S.F. Syed Fadzil is an Associate Professor at the Architecture Program, School of Housing Building and Planning Universiti Sains Malaysia. She received her B.Sc (Architecture Studies) and M.Arch from University of Nebraska Lincoln, USA. She continued her PhD study at University of Wales College of Cardiff UK. Dr. S.F. Syed Fadzil’s expertise involved environmental building simulations, thermal comfort and daylighting. Her current interests involved architecture education, the business of architecture and effects of liberalization and globalization to architectural practice. She is also Fellow member of CABE and an active member of the Malaysian CABE chapter.
Ali Ahmed Salem Bahdad is a lecture at the Architectural Engineering and Environmental Planning, Hadhramout University. He received his B.Sc (Architecture) from University of Hadhramout, Yemen, and his MS.c. (Architecture and Building Sciences) from King Saud University, Saudi Arabia. He is currently Ph.D. Candidature at School of Housing Building and Planning Universiti Sains Malaysia. His current knowledge areas and research interests focuses sustainable urban design, green buildings, high performance buildings, daylighting design and energy performance, and facade design and technology.
Ts. Farhana Mohd Razif is an Architecture lecturer at School of Housing, Building and Planning, Universiti Sains Malaysia Penang. She graduated with Master of Architecture and Bachelor of Architecture (Hons) from Universiti Teknologi Malaysia (UTM) Johor Bahru. Farhana’s research interest are on Building Information Modelling in Architecture, Sustainable Architecture, and Tropical Architecture. Her current interest involved shape grammar studies in architecture and architectural digitalisation.
This research paper was presented at the 2021 CABE Malaysia Chapter online Conference.