Comparative Analysis of Solar Rights from Neighborhood to Building Scale (Case Study: Yousefabad, Tehran)

Rapid urbanization has accelerated recently, bringing environmental and equity challenges, particularly in solar and daylight access. In Yousefabad (District 6, Tehran), rapid densification under current height codes threatens residents' daylight access. Accordingly, this study addresses these challenges by evaluating solar access and developing morphology-based height regulations that safeguard residents' right to sunlight, focusing on efficiency, equity, and the trade-offs between them in solar performance. This study adopts an applied, quantitative approach to evaluate solar radiation (SR), sunlight duration (S_H), and sky view factor (SVF) across three spatial scales—macro (neighborhood), meso (urban block), and micro (building) —to derive an optimized height. The workflow combines GIS-based analysis, parametric modeling in Rhinoceros, and environmental simulations in Ladybug and Honeybee, while a genetic algorithm optimizes design scenarios and Gini coefficients (G_SR, G_SH, G_SVF) quantify equity in solar access. Results indicate that current height codes restrict daylight and solar access compared to the optimized scenario. Based on the equity indicator and Gini coefficients, the optimized scenario reduced G_SR, G_SH, and G_SVF by roughly 16%, 20%, and 11%, while increasing mean SR, sunlight hours, and SVF by about 15–20%. These outcomes defined block-specific height bands and guidelines to help planners and policymakers enhance solar equity in dense areas. The main innovation lies in a unified analytical–optimization framework linking neighborhood, block, and building-scale evaluations. The proposed framework links urban form to solar equity, demonstrating that balanced height and density improve solar access in dense cities.