Cool coatings(solar reflective coatings)possess a high total solar reflectance and a high thermal emittance,and they have potential applications in building surfaces,pavements,and oil tanks.By decreasing the accumulation of heat,these coatings can reduce the urban heat island effect to increase thermal comfort and to decrease energy consumption in hot zones.In this work,a cool white coating based on waterborne acrylic was prepared.The reflectance and thermal emittance were measured using an ultravioletvisible-near-infrared spectrophotometer and the steadystate calorimetric technique,respectively.The cool coating possessed a total solar reflectance of 0.887 and a thermal emittance of 0.85.The linear fitting results indicated that the thickness of the dry film is an important factor that affects the reflectance and that the physical limit of total solar reflectance in practical cool coatings is 0.91.A homemade device developed according to military specification MIL-E-46096C was used to measure insulation temperature differences,and an insulation temperature difference of29°C was obtained.The above results demonstrated that the cool coating can be applied to buildings.
