Study of Cool Roof Paints with the Comparison of Different Artificial Illuminants with Natural Exposure

The sun irradiation of building is one of the important factor which influences the urban heat island effect. Cool and reflective surfaces permit to reduce the local temperature. Infra-red reflectance measurement using a spectrophotometer is the most used method to evaluate the effectiveness of “cool coatings”. However, the necessity of the evaluation of the real behaviour is very current. The purpose of the work is twofold. Check if simple temperature measurements allow the comparison on the thermal behaviour of organic coatings and secondly to identify which is the source of artificial light that best simulates the solar radiation. The properties of NIR reflective pigmented organic coating and the references are evaluated using three different radiation sources (incandescent infrared emitting lamp, tungsten halogen one, and xenon arc one) in comparison to the natural solar exposure. The thermal performances are evaluated by a roofless box where the panel and the internal box temperatures are checked by two thermocouples and the surface temperature by a IR thermo-camera. The xenon arc lamp best simulates the behaviour of roof coverings irradiated by natural solar radiation. According to temperature and reflectance data, the studied NIR pigmented coating shows a comparable behaviour as TiO2 based coating.