Development of a retro-reflective material as building coating and evaluation on albedo of urban canyons and building heat loads

Retro-reflective materials (RRM) applied as building coatings are a possible means to help counter urban heat islands. In this research, to improve the durability and reflective performance of RRM before applying it as a building coating, we have developed a new type of RRM by adding a glass covering with high transmission and high strength, and investigated its durability and retro-reflective performance by evaluating changes in solar reflectance and retro-reflectance for a period of 485 days. There was almost no degradation on the surface of RRM, and both its solar reflectance and retro-reflectance showed no significant decrease for the period. Its solar reflectance remained around 0.81, and retro-reflectance around 0.44. Additionally, we simulated the influence of building surfaces with different reflective characteristics on the albedo of urban canyons. A building surface with RRM is the most effective, compared to other materials with diffuse or mirror reflective characteristics. Finally, the influence of RRM coating on building thermal loads was simulated. The cooling loads and the total annual thermal loads were both reduced. Thus, it is possible to apply it as a building coating to both mitigate the heat island and reduce the building thermal loads.