Résumé

Facades represent an important part of urban envelop in dense areas. They play a major role in the thermal comfort of pedestrians as well as on the city (in)-ability to stay reasonably fresh during the day or to cool at night. This study focuses on differences in thermal comportment of different kind of vertical éléments – heavy or light, pale or dark, absorbent - reflective or transparent based on measurements of different real situations. The study shows the differences between vertical surface’s temperatures but also highlights the differences of speed at which surfaces reach their highest temperature and so the time necessary to cool after solar exposure. Finally, it also underlines the ability of reflective surfaces (eg. glass facades) to worsen the comfort of pedestrians by adding up to 40% of incoming solar radiation intensity. Findings from this study show that surfaces do not only affect the apparent temperature by adding up to several degrees but also to a lesser extent the urban heat island effect. These results show the importance of material and constructive choices regarding the mitigation of exacerbation of global warming in cities.

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