Abstract:
Bangladesh's rising energy demand and the need for sustainable built environments have made green building designs increasingly popular. However, the growing trend of practicing Leadership in Energy and Environmental Design (LEED)-certified green buildings in Bangladesh primarily focuses on using energy-efficient equipment. In Dhaka, many office buildings feature fully glazed façades, which minimize the need for artificial lighting but cause excessive daylight penetration, resulting in glare, solar heat gain, and increased energy consumption for cooling. Optimizing architectural parameters during the design phase can significantly lower energy consumption. The building envelope plays a key role in energy regulation, with its design significantly impacting heat gain and loss. In warm and humid areas, i.e., Dhaka, reducing the window-to-wall ratio (WWR) can help minimize solar heat gain but may also increase the need for artificial lighting. To counteract heat gain through large openings, the use of shading devices is essential. However, improper shading can reduce daylight availability, so careful design of façade parameters for each orientation is necessary to ensure adequate daylight while avoiding increased energy consumption. Therefore, there is a need for optimization strategies that identify the appropriate parameters for façade design elements, ensuring a proper balance among various building performance metrics, such as daylight, energy use, visual comfort, and thermal comfort.
This research aims to optimize façade parameters (WWR ratio and horizontal shading depth) in Dhaka's office buildings to enhance daylight, ensure visual comfort, and reduce energy consumption. The study employed quantitative, computational, and analytical techniques and followed a four-step framework. The study began with an extensive literature review to identify key façade predictors. In the second phase, Rhino and Grasshopper were used to create a parametric test model for daylight and energy simulations. The models were then merged and analyzed in ClimateStudio and Octopus with genetic algorithms for optimization. Finally, the results were statistically evaluated through scatterplot analysis, which highlighted the trade-offs between daylighting and energy efficiency. A frequency distribution of façade design variables in Pareto-optimal solutions was conducted to identify effective value ranges for crucial façade design parameters. This analysis ultimately led to a sensitivity assessment of these parameters to ensure optimal performance. To visually analyze the optimum solutions, the Design Explorer was utilized effectively.
The research identified optimized façade solutions achieving sDA300/50% values over 90%, ASE1000, 250h below 10% and an average EUI of 256.66 kWh/(m²y). Increasing the WWR on north and south façades enhances daylight, while reducing it on east and west façades controls solar exposure and lowers EUI. The study highlights that deeper shading on south, east, and west façades further decreases EUI. An ideal façade design includes high WWR on the north (80-100%), moderate to high WWR with deep shading on the south (51-100%), and low WWR with deep shading on the east and west (11-30%). This balanced approach optimizes daylight quality, solar control, and energy efficiency, showcasing a multi-objective optimization method that supports architects in making informed early design decisions. The potential for net-zero buildings may exist if other factors are further explored.