On the ageing of cool roofs: Measure of the optical degradation, chemical and biological analysis and assessment of the energy impact

• The ageing of two cool roofs in Greece is documented through experimental procedures.
• Chemical and biological analysis in roof samples indicates the factors that contribute to the ageing.
• The maintenance of the cool roofs properties is documented through a number of experiments.
• Estimation of the effect of the cool roofs ageing on the thermal comfort of the buildings.

The use of cool materials for heat island mitigation has gained a lot of interest during the past few years. Cool materials are characterized by high solar reflectance and infrared emittance values. To maximize cooling energy savings, high albedo roof coatings should maintain the above properties for the service life of the coating. The aim of the present paper is to analyze the weatherisation of the cool roofs in two buildings in Athens Greece. The optical properties of the aged and new cool roofs are measured and compared. The impact of ageing in the two buildings’ energy performance is estimated. A mineralogical analysis is performed in order to quantify the deposition of pollutants on the cool roofs’ surface. In addition, a series of microbiological tests are implemented to reveal the impact of ageing and weatherisation in health. In both school roofs the surface temperature has a significant decrease between the part of the existing cool coating and the application of the new part with a temperature difference reached reaching 7–12 K.