Citywide Assessment of Urban Tree Shading on Roof and Facade Solar Radiation Using Semantic 3D City Models

Abstract. Urban trees regulate solar radiation on building surfaces, influencing urban climate and energy performance. Using a semantic 3D city model, tree shading was quantified for all roofs and façades across the city of Munich, Germany. Solar irradiation was simulated for scenarios with and without trees using a tool supporting detailed 3D shadow analysis and urban-scale assessments, computing irradiation at 43 million points per scenario. Spatially explicit, surface-resolved shading effects were derived by comparing irradiation between the scenarios, isolating the impact of trees. Tree shading reduced annual global solar irradiation on buildings by 7 809 GWh (−11%). The reduction on facades (18%) was three times larger than on roofs. On roofs, direct and diffuse decreases balanced; facades showed a stronger drop in direct irradiation. Buildings taller than 15 m received only minor roof shading, while facade shading was measurable at all heights but diminished with increasing building height. Assessment of the vertical distribution of tree shading on facades revealed height‑dependent reductions of 45–50% at ground level, 14–18% at 10 m, and ≈ 3% at 20 m; these values were consistent across different facade orientations. Nevertheless, south‑facing facades consistently received higher absolute solar irradiance. These results quantify how tree shade varies with building morphology and provide a comprehensive overview of its cumulative impact across the city of Munich. The semantic structure of the 3D city model enables flexible aggregation and analysis down to individual building-envelope surfaces, a key added value that supports morphology-dependent assessments and informs the planning of sustainable and resilient urban environments.