The effective landscape design parameters with high reflective hardscapes: guidelines for optimizing human thermal comfort in outdoor spaces by design -a case on hot arid climate weather

Abstract Effective landscape design, which optimizes solar irradiation and absorbed heat to reduce mean radiant temperature (MRT), is critically important for enhancing outdoor thermal comfort, particularly given the ongoing global decline in vegetated areas. Using Cairo, Egypt as a case study, it examines how variations in design layouts and surface materials influence reflected solar energy and, consequently, the urban thermal climate. The research introduces a novel approach by integrating generative design and parametric modeling to optimize urban park microclimates, offering a structured methodology for sustainable and climate-resilient urban spaces. A parametric modeling approach was employed to test various landscape configurations, adjusting paving size, material distribution, Rotation angle for Landscape, and tree placement. Over 1,500 design cases were simulated and analyzed using the Climate Studio plugin for Grasshopper 3D. Through generative design algorithms, an optimized framework was developed to identify effective strategies for urban cooling. Findings indicate that smaller, scattered hardscape patterns with maximum 6% divided ratio, combined with light and dark surfaces, wood, and softscape areas, significantly reduce reflected solar energy. Tree placement over light-colored hardscapes proved effective in lowering solar reflection, while optimal hardscape tile rotations towards to northern orientation. Multi-variable scenarios optimization incorporating trees, water surfaces, and reflective materials achieved up to a 44% reduction in solar irradiation. These results highlight the importance of balancing hardscape and softscape areas, integrating vegetation and water features, and utilizing light-colored materials in dispersed patterns. The study provides actionable insights for urban planners and landscape architects to design sustainable, climate-adaptive cities.