Application of retro-reflective materials in urban buildings: A comprehensive review

Abstract High-rise and high-density buildings are increasing with the rapid urban development, which leads to many urban thermal environment problems represented by the urban heat island. The traditional highly-reflective materials can reduce the solar radiation gain of buildings to alleviate urban heat island by the diffuse reflection, but the reflected solar radiation will be absorbed by the surrounding urban surfaces and thereby, the urban heat gain will not be reduced or even increased due the multiple absorption of thermal radiation in building groups. To overcome the inherent defect of highly-reflective materials, retro-reflective materials were proposed to reflect solar radiation along the incident radiation and had gradually attracted much attention due to their unique reflection characteristics. However, the review on retro-reflective materials has not been published to summarize the development status and potential deficiencies of retro-reflective materials. This review focused on the development, performance measurement and significant outcomes of retro-reflective materials, while the application efficiency of retro-reflective materials was described on urban thermal environment and building energy consumption comprehensively. Finally, future directions were proposed on possible studies and applications.