Dynamics of Cool Surface Performance on Urban Microclimate: A Full-Scale Experimental Study in Singapore

Abstract

Urban Heat Island effect is one of the most important human-induced impacts to urban climate. Construction materials absorb solar radiation and as a result, higher sensible heat is released to the environment which contributes to the air temperature changes in the urban environment. Built-up surfaces such as roofs, walls and roads, when covered with cool surfaces have significant potential in reducing heat absorption by reflecting the radiation back to the atmosphere. In this paper, we presented experimental analysis of thermal exchanges between the buildings and environment, while evaluating the performance of cool coated surfaces in improving the urban microclimate. Temporal values of air temperature, surface temperature, sensible and latent heat fluxes are monitored in a fullscale street canyon located in the tropical climate of Singapore, where a side-by-side comparison between a cool and a conventional canyon has been made during a period in summer. The combined effect of a cool roof, a cool wall and a cool road are observed to have up to 30% reduction in sensible heat release from the built-up surfaces which contributes to the ambient air temperature being up to 2°C lower than a conventional setting. As a result, pedestrian thermal comfort is improved by having up to 1.5°C reduction in terms of Universal Thermal Climate Index (UTCI). The paper also presents a critical analysis of pedestrian comfort due to the cool road in the middle of the street canyon.

Keywords: Urban Heat Island, UHI Mitigation, Cool surface, Tropical climate, Urban Microclimate, Outdoor comfort