Investigating Window Design Impact on Ottv Through Bim Modeling in Warm-Humid Cities

Introduction: Fenestration design is critical for building energy efficiency in warm-humid climates, where solar radiation through windows significantly affects the overall thermal transfer value (OTTV). Many buildings in Indonesia do not adequately address location-specific envelope design, potentially due to limited experimental research on appropriate designs for Indonesia’s diverse climates. Purpose of the study: This study aims to examine the impact of different window design strategies on building thermal transfer across Indonesian cities. Methods: A sensitivity analysis was conducted to evaluate the influence of window design on the OTTV in three geographically distinct Indonesian cities: Banda Aceh (Northern Hemisphere), Pontianak (Equator), and Yogyakarta (Southern Hemisphere). Using a building information modeling (BIM)-based OTTV calculator in Autodesk Revit and Dynamo, 3,600 window variations were generated and represented in 180 line graphs. Variations included window-to-wall ratio (WWR), glazing properties, and shading devices. Results: The analysis indicates that WWR has a more significant effect on the OTTV than the shading coefficient (SC), with reductions of up to 46 W/m² when WWR decreased from 65 % to 25 %. Shading dimensions proved more influential on the OTTV than glazing properties, highlighting the critical role of shading configuration in thermal performance. Optimizing WWR and implementing standardized shading systems can significantly enhance energy efficiency and thermal comfort, especially in tropical climates with high solar exposure. These findings encourage early design-stage exploration of WWR and shading combinations to achieve compliance with energy standards while maintaining design flexibility.