Appraising the influence of paving materials on pedestrian thermal stress in tropics: evaluating the effects of tree shading on surface thermal performance

Abstract

Escalating trend in the formation of urban heat island (UHI) in the cities of tropical Asia contributes to warming microclimates and imposes a greater challenge on human health and well-being. Rapid urbanization and declining green plot ratio has contributed to the formation of an UHI in the city of Colombo. Consequences of UHI on urban green spaces exaggerate with the increasing use of paved surfaces. As surface heat inflation causes thermal discomfort for dwellers, it is vital to understand the thermal performance of different artificial and natural paving materials with a particular focus on tree shade variation. This study experimentally investigated parks of Independence Square and the Water’s edge in Colombo. Onsite field investigation was performed on a typical hot season identifying most users perceive settings inside the park. The Mean Paving Surface Temperature (MPST) and predicted Physiological Equivalent Temperature (PET) values were obtained in relation to Crown Volume Coverage (CVC) of trees. Results explicitly confirm PET values inside the parks correspond to high discomfort range. Exposed concrete paving is evident for high PET levels and the shaded surfaces are apparent for a reduction of 10°C of mean MPST. The Lowest PET of 30 °C was evident over the shaded grass paving with 31°C mean MPST. Reduction of the MPST significantly correlated (p=0.00) with increasing tree CVC. Thus, the findings of the study inform natural paving design implications with improved shading composition can promote less heated urban green spaces in developing cities of tropics.