Calculating Cost-Optimal Energy Efficiency Levels for Opening Elements on an Exemplar Residential Building

This study presents a comprehensive approach to enhance the energy performance of a multi-story residential apartment in a temperate region of Turkey. The strategy focuses on cost optimization in compliance with EPBD Directives and CEN EN 15459-1:2017 standard. It addresses energy consumption and environmental impact associated with glazed building components and openings, considering key factors like primary energy use, energy costs, CO₂ emissions, and annual heating, cooling, and lighting energy consumption throughout the year. The building energy simulation (BES)-based optimization process involves the design variables that exert a significant impact on energy efficiency. These variables encompass window size, window-to-wall ratio, solar shading systems, glazing material properties, window frame composition, and profile dimensions. EnergyPlus and DesignBuilder with genetic algorithms facilitate this process. The study explores trade-offs among design alternatives and identifies building envelope configurations that improve energy performance and reduce costs compared to the reference building. Compared to the reference case, the energy-efficient cost-optimum solution achieved savings of 23.7% in primary energy (29.1 kWh/m²), 21.4% in global costs (44.4 €/m²), and a 24.4% reduction in carbon emissions (above 8 kg/m²). These results emphasize the benefits of using simulation-driven optimization in early design stages to meet energy efficiency and environmental goals.