Optimizing urban block layouts and density distribution: A generative design framework for neighborhood performance

Purpose – In many countries, urban block layouts follow rigid and outdated design guidelines; however, these approaches fail to effectively address settlement construction, neighborhood planning, the design of old urban contexts and the rapid development of emerging cities, as seen in the new towns of Iran and various other regions worldwide. Revising these guidelines requires early-stage decision-making to evaluate building layouts based on their impact on the built environment. This study introduces a workflow for optimizing urban block layouts with constant density while considering design constraints, climate and environmental performance. This framework assists planners and policymakers in refining site density distribution and building massing. Design/methodology/approach – A computational urban design method was developed utilizing a grasshopper-based algorithm and Python for data generation. It introduces an innovative approach by incorporating buildings' placement coordinates as design variables alongside dimensions and orientation. The Wallacei tool optimizes layouts by considering energy use intensity (EUI), outdoor thermal comfort and facades' received radiation employing Ladybug Tools. Spatial daylight autonomy (sDA) and urban heat island (UHI) effects are also integrated into the workflow. The framework is applied to a hypothetical residential district in Tehran, consisting of nine blocks, each containing nine plots. Findings – The results for a set of optimal solutions demonstrate that beyond existing urban design policies, environmentally prioritized designs are achievable. Radiation differences between the optimal models and the conventional parallel layout range from 41.3 to 61.1%. However, changes in EUI and universal thermal climate index (UTCI) are minimal; significant improvements are observed in sDA, with 7, 8 or all 9 buildings meeting the acceptable threshold compared to none in the parallel layout. These findings highlight the effectiveness of the design method framework proposed in this research, which has the potential to significantly influence urban planning practices across various regions globally. Originality/value – The methodology of this study provides a flexible decision-making framework for early design phases, enabling policymakers, architects and urban designers to address the gap between current urban design methods and environmentally driven approaches. Sensitivity analysis of optimal solutions further offers valuable insights into the correlation between design variables and evaluation metrics.