“An Energy-Free, Low-Cost and High Cooling Performance Passive Radiative Cooling TecOur Team won the Champion Prize in the 2020/2021 Environmental Paper Award held by The Hong Kong Institution of Engineers (HKIE) Environmental Division. The awarded paper is entitled “An energy-free and low-cost daytime passive radiative cooling paint for energy saving in buildings and decarbonization”. In this paper, the working principle and fabrication method of a novel daytime passive radiative cooling paint have been illustrated, and its cooling performance and the energy-saving potential in real building applications have been demonstrated. This paper not only provides an environmentally friendly solution to environmental issues (i.e. energy shortage and global warming) caused by building cooling systems, but also facilitates the green building evolvement and sustainability development.