Contribution of different pavements to pedestrian heat stress under heatwave conditions

In order to adapt to climate change, cities are studying various urban cooling techniques to improve pedestrian thermal comfort of users during heatwaves including urban greening and cool materials. One technique being considered by the City of Paris is cool pavements. To this aim, an experimental test site has been constructed and instrumented to study the thermal and climatic behavior of candidate sidewalk structures.

 

The experimental demonstrator is located in Bonneuil-sur-Marne near Paris, France. This experimental device consists of 16 samples of various sidewalk structures. Each sample is approximately 4x4m accros by 25cm deep and is composed of several layers following real-world conditions. The samples are instrumented with temperature and heat flow sensors at several depths, with the data recorded every 5 minutes. Additional weather measurements are also conducted onsite to monitor air temperature and humidity, global horizontal short- and longwave irradiance as well as wind speed and direction.

 

This communication focuses on data collected during a four-day heatwave during summer 2022. Measurement data from each structure is analyzed with the aim of evaluating their contribution to pedestrian heat stress urban climate in terms of convection and radiosity during the day, in the evening and late at night. This requires calculating to convective heat exchange coefficient over time in order to properly distinguish daytime, evening and nighttime. Finally, the cumulative effects of the series of hot days are also analyzed.

 

The implications of these analyses on pavement structure selection for cities aiming to adapt to heat waves is discussed.