Envelope Design Trade-offs for Low-carbon Residential Buildings in Dubai: A Simulation-based Multi-objective Optimization Study

Residential buildings in Dubai experience high cooling demand due to extreme climatic conditions, increasing both operational energy consumption and carbon-related environmental impacts. While previous studies have commonly focused on operational energy reduction, fewer investigations have simultaneously examined thermal comfort and embodied carbon implications within residential envelope optimization. This study investigates envelope design trade-offs for low-carbon residential buildings in Dubai through a simulation-based multi-objective optimization framework. A two-story residential villa prototype was developed in DesignBuilder and evaluated under Dubai climatic conditions using an EnergyPlus simulation engine and hourly weather data. Five envelope-related variables were optimized, including window-to-wall ratio, glazing type, external shading depth, wall construction, and roof construction, while occupancy, HVAC performance, ventilation, and operational schedules remained fixed. Optimization was conducted to identify balanced envelope solutions based primarily on annual site energy consumption and thermal discomfort, while embodied carbon was retained as a supporting material-impact indicator. The baseline model recorded an annual site energy use of 40,427.48 kWh/year, corresponding to 189.44 kWh/m²·year, with 3,036.50 annual discomfort hours. Optimized solutions achieved reductions in annual site energy use to approximately 18,107 kWh/year, representing an improvement of nearly 55% relative to the baseline case. Results consistently favored moderate window-to-wall ratios, low-emissivity glazing, insulated roof assemblies, and external shading strategies. The findings provide practical guidance for climate-responsive residential envelope design in Dubai and contribute evidence for balancing operational and embodied environmental performance in cooling-dominated climates.