Development of Two New Types of Retroreflective Materials as Countermeasures to Urban Heat Islands

Abstract

In this study, the side effects of high-reflective and ordinary retroreflective materials, used as countermeasures to urban heat islands, are discussed. In addition, two retroreflective materials are proposed in order to avoid these adverse effects. These materials could be applied to roads and building exteriors to reduce their heat absorption from solar radiation. The first proposed type is the directional retroreflective material, which reflects light only during summer; therefore, it reduces the cooling load in summer, reduces the heating load in winter, and prevents light pollution at night. However, its structure is complicated and fragile; thus, it is suited for small areas, such as roofs and walls. The second type is the rough-surface retroreflective material, which shows weak retroreflectivity but can withstand distortion; thus, it is suited for roads. These two types require little maintenance, because they have no moving parts. Hence, these materials would not experience any breakdown, which is a great advantage for roads and building materials. Combining high-reflective, ordinary retroreflective, directional retroreflective, and rough-surface retroreflective materials, and assigning each type to the appropriate application would form an advanced mitigation system against urban heat islands.