This project aims to promote a novel energy-free and environment-friendly passive radiative cooling paint (patented in Hong Kong) for energy-saving and decarbonization. The self-developed and high-performance paint features the edge in solar reflection and thermal emission, resulting its significant sub-ambient cooling effect, without consuming electricity and ozone-depleting refrigerants. We have demonstrated its high effectiveness and wide applicability in various scenarios. Most notably, in a site-building use case (supported by the HKSAR), by applying the cooling paint, the roof surface and the indoor air temperature could be reduced by 20-30 ⁰C and 5-6⁰C, respectively, leading to the 8-10% cooling energy saving potential. Empowered by the remarkable R&D outcomes and the vibrant market environment, the related market potential can be exploited in this project and a promising business prospect is anticipated. We will collaborate with different parties and organizations in building, energy and paint industries to effectively demonstrate and promote our paint product. Continuous product and business upgrade will also be conducted to maintain our technical competence and business sustainability. Our ultimate goal is to achieve remarkable environmental and social impacts, mitigating the energy shortage and climate change, while facilitating overall sustainable development and economic growth in Hong Kong.