Road cooling in tropical environments: microclimate modelling of pavement cooling scenarios using ENVI-met

Abstract Urban Heat Islands (UHIs) have exacerbated temperature differences between cities and their surrounding areas, leading to heightened heat-related challenges such as reduced thermal comfort, health issues, increased building energy consumption, and environmental degradation. Considering that road and parking pavement typically occupy 30% of urban areas, exploring cooling technologies for this infrastructure is imperative. This study uses ENVI-met microclimate modelling software to evaluate the impact of pavement surface albedo on temperatures and thermal comfort in a tropical urban area. The model, validated against microclimate data, explored cooling scenarios using cool pavement technologies such as light-coloured aggregate, white-topping, super heat reflective coating, and passive radiative cooling coating, compared with uncoated black asphalt. Higher albedo values were found to reduce surface and air temperatures but increase Physiological Equivalent Temperature (PET), indicating reduced thermal comfort. An albedo increases from 0.06 to 0.8 can reduce surface temperature by up to 25.3°C and air temperature by up to 3°C. The increase in PET is likely due to reflected radiation being absorbed by road users and nearby buildings. This highlights the need for retro-reflective coatings to mitigate local heating effects. In this study, strategies to mitigate UHIs were proposed. While super-reflective coatings are effective in reducing temperatures, they may decrease thermal comfort due to higher PET values. However, this negative impact can potentially be mitigated using retro-reflective technologies.