Cool Facades and Pavements: Mitigating Heat Stress and Improving Urban Thermal Conditions in Affordable Housing Project – a Case Study in Thailand

Abstract

An increase in urban air temperature raises heat stress and mortality risk for city dwellers. This study assessed the potential reductions in air temperature and heat stress through the combined effect of cool façades and floor pavements, in two street canyons in an affordable housing project in Thailand. The air temperature and mean radiant temperatures were simulated for 81 design scenarios where materials with low, medium, and high albedos were used for the walls of buildings, parking areas, and road using ENVI-met v5.0. The risk of exposure to heat stress under extreme conditions was estimated using a heat index equation. The results showed that the avenue canyon (height-to-width ratio, H/W = 0.6) with a low-albedo road surface was hotter than the regular one (H/W = 1.2), due to the larger areas of road pavement and smaller shaded areas. A medium to high albedo for the pavements could reduce the street-level air temperature by up to 2.3°C, but the average mean radiant temperature was raised by 9.3°C. The regular canyon (H/W = 1.2) provided better thermal conditions, and had fewer 'hot spot' areas exposed to heat stress than the avenue canyon. This study explored the benefits of using cool pavements to improve the thermal conditions in areas with limited shade. In addition, this study identified safe outdoor areas not being directly exposed to solar radiation during the hot summer months. These findings could be important for planning safe outdoor activity spaces under extreme heat conditions.