The impact of setbacks on solar access: a GIS-based shadow analysis in Khulna’s neighbourhood

Setback regulations, a fundamental component of urban planning and development control, are frequently overlooked in Bangladesh, thereby compromising the principles of urban sustainability. This study examines the critical role of setbacks in ensuring adequate solar access within the Nirala Residential Area—a formally planned neighbourhood in Khulna City. Utilising ArcGIS 3D analysis tools, the research quantified structure shadow volumes during the summer and winter seasons of 2023. The study explored the impact of incremental increases in setback distances beyond current regulatory standards on solar access. Shadow volumes were assessed at distinct intervals—3.00 pm, 3.15 pm, and 3.30 pm during summer, and 2.00 pm, 2.15 pm, and 2.30 pm in winter—to evaluate temporal and seasonal variations. The findings indicate a clear seasonal dependency in sunlight accessibility, significantly influenced by setback dimensions. Specifically, a 15% augmentation to existing setback standards emerged as the most effective, yielding reduced shadowing in winter and enhanced shading during the hotter summer months. This research provides valuable insights for urban policymakers and planners, underscoring the potential of setback regulations in fostering sustainable urban environments. By advocating for revised and more context-sensitive setback guidelines, the study promotes improved living conditions, public health, and environmental quality through greater access to natural light and the creation of climate-responsive neighbourhoods.