Cool materials for reducing summer energy consumptions in Mediterranean climate: In-lab experiments and numerical analysis of a new coating based on acrylic paint

Highlights: • Paper investigates potentiality of 3paints of automotive sector for cool roofing application. • Laboratory measurements are performed for different substrates and configurations. • Acrylic paint has satisfying values of spectral reflectance (77–80%) and thermal emissivity (92%). • Numerical analyses are proposed for roof technologies with different insulation level. • Annual energy saving varies between 0.4% and 3.0% and roof never exceeds temperature of 40 °C. - Abstract: The urbanization has negative effects on the environment, mainly related to the generation of pollution, the modification of the properties of the atmosphere, the covering of the soil surface. The cumulative effects produce the so-called phenomenon of 'Urban Heat Island' (UHI). Cool roofs have a positive impact on the global environment, by reducing the energy required for interior cooling and related greenhouse gas emissions. Moreover these help to mitigate the UHI effect. A cool roofing material is characterized by higher solar reflectance in comparison to conventional roof coatings and high infrared emittance values. This paper is aimed to investigate the potentialities of high reflective commercial products not specialized for cool roofing. Three paints of the automotive sector have been selected. These products have very fast drying, good adhesion directly to different type of materials, good gloss and appearance, greater durability than traditional, lower cost and application time. Laboratory measurements are performed for the characterization of thermal-optical properties of different prototype samples, by considering application on different substrates (aluminum, ceramic tile, bitumen membrane, polyvinyl chloride sheet) as well as different configurations (evaluating the adoption of gripping and external gloss). Only the white acrylic paint shows good values for spectral reflectance (77–80%) and thermal emissivity (92%) that are comparable with commercial products. The artificial accelerated weather resistance tests and natural exposure effects have been also evaluated. Then, several numerical analyses are proposed for a real case study and some roof technologies also with different insulation level. The main evaluated indexes are the seasonal and annual energy savings, the reduction of polluting emissions and the cost effectiveness. Globally summer benefits are very satisfying meanwhile the annual energy saving varies between 0.3% and 3.0%.