1,1,- 1AiEM Architecture, Energy and Environment, Universitat Politècnica de Catalunya, Barcelona, Spain
- 2Department of Architecture and Urban Studies (DAStU), Politecnico di Milano, Milan, Italy
- 3SOS urban Lab, DICEA Department, Sapienza University of Rome, Rome, Italy
Shade provision by buildings and trees is very beneficial in reducing pedestrian heat stress in hot climate regions, such as the Mediterranean. However, shade is not constant in time and space, which makes difficult to understand its actual potential to reduce pedestrian heat stress depending on the geometry and orientation of each urban space and the time of the day.
In this work we present a framework to generate district-scale heat stress frequency maps based on the spatiotemporal variability of mean radiant temperature at the street level. This allows understanding the beneficial effect of a district urban geometry and vegetation on the thermal conditions of its urban spaces, as well as to identify where and when more shade is needed to reduce pedestrian heat stress.
The approach is applied to the Gràcia district of Barcelona. First, we carried out high-resolution simulations of the radiation fluxes across the urban area using the SOLWEIG model. Then we correlated the Mean Radiant Temperature (Tmrt) to the PET values in the same points, to identify threshold values corresponding to different heat stress levels. Finally, we cross compared the spatial (maps) and frequency (histogram) distribution of Tmrt values across the whole district over different times of the day.
The results indicate that shade provision by urban geometry reduces pedestrian heat stress from extreme to moderate levels in the morning (until 12:00 local time) and afternoon (starting from 16:00). In the time window from 13:00 to 15:00, urban geometry has negligible impact due to high solar elevations, while trees shades significantly reduce heat stress from beyond extreme to moderate levels.
Based on the results, we generated a cumulative heat stress frequency map that can be used as a practical tool to plan district-scale shading interventions enabling acceptable thermal conditions across the whole urban area.
How to cite: Salvati, A., Colaninno, N., Lopez-Besora, J., and Morganti, M.: How much shade do we need to reduce pedestrian heat stress? Understanding the spatiotemporal variation of the urban thermal environment at the district-scale, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-654, https://doi.org/10.5194/icuc12-654, 2025.
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