Highly-reflective coatings (HR-coatings) are used to reduce the building heat gain and thereby, alleviate urban heat island, but the solar radiation reflected by HR-coatings will be absorbed by the surrounding building surfaces and solar heat gain will not be reduced or even increase. To overcome this inherent optical defect of HR-coatings, Retro-reflective coatings (RR-coatings) are proposed to reflect solar radiation along the incident direction with the potential to improve the urban thermal environment. Selecting the reasonable reflective coating is important to improve outdoor thermal environment, especially for high-density enclosed building groups. According to this aim, RR-coatings and HR-coatings were covered on two small-scale models of high-density enclosed building groups. The regional albedo, wall temperature and air temperature were taken as the evaluation parameters to compare the impact of RR-coatings and HR-coatings on the regional thermal environment of the high-density enclosed building groups. Experimental results showed compared with HR-coating model, RR-coating model had better cooling potential, and its peak regional albedo was increased by 5.0%. And air temperature in enclosed space of RR-coating model was 2.3℃ lower than that of HR-coating model, but they were higher than outdoor natural air temperature. Moreover, compared to HR-coatings, covering RR-coatings could reduce the peak and average wall temperature by 2.5℃∼15.2℃ & 0.3℃∼3.8℃ in the daytime and 1.3℃∼7.9℃ & 0.2℃∼4.4℃ in the nighttime, and its application in the roof and east wall had the higher efficiency.

Xi Meng (Innovation Institute for Sustainable Maritime Architecture Research and Technology, Qingdao University of Technology), Congbao Xu (Innovation Institute for Sustainable Maritime Architecture Research and Technology, Qingdao University of Technology), Weijun Gao (Innovation Institute for Sustainable Maritime Architecture Research and Technology, Qingdao University of Technology and Faculty of Environmental Engineering, the University of Kitakyushu)

Jing Wang, Shuhan Liu, Zefang Liu, Xi Meng, Congbao Xu, Weijun Gao, An experimental comparison on regional thermal environment of the high-density enclosed building groups with retro-reflective and high-reflective coatings, Energy and Buildings, Volume 259, 2022, 111864, ISSN 0378-7788, https://doi.org/10.1016/j.enbuild.2022.111864.