Enhancing Outdoor Thermal Comfort in Hot-Climate Dense Cities through Artificial Shades: Optimizing Shade Geometry and Spatial Allocation

Shading is a simple yet effective intervention for mitigating extreme urban heat, especially in hot climates. In dense areas, where urban morphology is already established, artificial shading - such as engineered and lightweight structures - offers great potential to transform outdoor spaces. By enhancing pedestrian comfort, such interventions contribute to the usability of those spaces to their full potential, as well as the well-being of their users.

While research shows that dense tree canopies generally provide higher cooling performance, relying solely on natural shading presents major challenges. Ensuring adequate soil, irrigation, and maintenance for tree-planting - particularly in large-scale applications - is often unfeasible in compact urban environments where open space is limited. Artificial shading on the other hand offers greater flexibility, with opportunities to establish, not just comfortable spaces, but also pleasant destinations that bring communities together. Research on artificial shading, however, remains limited compared to other shading means, with currently no widely agreed-upon framework available to support environmentally-aware pedestrian-focused designs.

New approaches to environmental analysis and evaluation of shading are increasingly being established in current research, utilizing the evolving capabilities of simulation tools. These methods support designers' decision-making process, especially during early design phases, but they vary widely in approaches, parameters, and applicability. There remains a need for more foundational, general, transparent, and analytical frameworks that establish a core for optimization; not only evaluating shading performance but also clarifying how different parameters influence outcomes. Establishing such frameworks is the central aim of this research.

To support this, the study focuses on two core dimensions of shading design: geometry and spatial allocation. Three optimization methods were developed using Ladybug-Tools within Grasshopper's parametric platform. The first method establishes a base approach that identifies critical shading periods across the year to support designs targeting varying seasonal needs. The second and third methods are comparative, geometry-based, analytical frameworks, addressing open and continuous shading configurations, respectively.

The first method was tested in urban canyon contexts with varying orientations and height-to-width ratios, and in two distinct climates, using weather files for Cairo and London. The method relied on UTCI for thermal comfort evaluation. Results revealed substantial differences in shading requirements between the two climates and across morphological variations. In Cairo (H/W=1.3), results showed that 8.5% (N-S) and 18.7% (E-W) of annual hours can highly benefit from shading, compared to only 1.4% in London, highlighting the strong influence of climatic context. Also, the highly beneficial shading hours in Cairo (E-W) extend for 10 or more hours per day for 103 days of the year, highlighting the significance of addressing outdoor shading in hot-climate urban environments. The method was further adapted to identify severely critical periods, demonstrating flexibility for refinement and outcome variation.

The second and third methods were applied to the Greater Cairo context, using a representative study area (The Mohandessin), and urban canyon morphology. Results highlighted the significant influence of minor variations in design or spatial allocation on shading performance, respectively, even when maintaining equivalent shade material. Beam layout and rotation variations resulted in substantial differences in direct solar exposure (DSE), with beam rotation angles alone producing variations of up to 59.5% and 40% during the severely hot weather period (SHWP) in N-S and E-W orientations, respectively. The third method further demonstrated that different spatial allocations play a critical role in performance outcomes, with certain configurations consistently outperforming others regardless of orientation change, Moreover, variations in shade height showed limited impact in some cases but noticeable effects on others depending on orientation. The method also introduced a novel heat-retention potential (HRP) parameter to capture the combined effect of ground heat absorption and sky view factor, while highlighting the influence of different ground materials and functions on performance outcomes. These findings emphasize the importance of optimization for improved shading efficiency and effectiveness.

The proposed methods provide a flexible and structured framework for comparative evaluation and performance-driven design. They present detailed comparative evaluations, showing the impact of shading variations on each criterion separately, while also proposing an overall scoring method to highlight optimal solutions, which encourages designers' and researchers' involvement, offering flexibility for further advancement and potential integration of additional parameters. Together, the three methods provide general, flexible, foundational, transparent, and complementary frameworks for artificial shading optimization.