In recent years, especially, the climate change (CC) and urban heat island (UHI) effects are becoming serious problems, affecting people’s life and health, especially in hot summer. For large cities such as Tokyo or Osaka in Japan, the UHI effect is particularly intense. It is known that about 40% of urban anthropogenic heat comes from buildings in large cities. To reduce the anthropogenic heat from buildings is an important countermeasure to this problem.
Strategies for UHI mitigation include urban ventilation, urban greening, green roof, highly reflective (HR) roads, and HR building envelopes, etc. In order to mitigate the urban heat island phenomenon and reduce the building cooling heat load, it has been common to apply the building envelopes because it is easy to apply and free of maintenance.
However, the effect of HR coating materials on urban outdoor thermal environment have not been thoroughly studied. In addition to the HR coatings, it is considered that the outdoor airflow and building coverage ratio possibly affect the outdoor thermal environment. This study aims to use Computational Fluid Dynamics (CFD) analysis method to predict the outdoor thermal environment, including three thermal sensation index: 1) outdoor temperature, 2) wet bulb globe temperature (WBGT), and 3) new standard effective temperature with consideration of outdoor solar radiation (hereinafter abbreviated as OUT_SET*) by varying the parameters of solar reflectivity, wind speed and building coverage ratio, and the results are reported in this study.