Nanobased coatings with improved NIR reflecting properties for building envelope materials: development and natural aging effect measurement

摘要

A significant contribution to the reduction of the Urban Heat Island effect and cooling energy demand is\udgiven today by the so called cool materials for the building envelope with enhanced reflecting and emitting\udproperties. The present study shows some preliminary results of the EU project COOL-Coverings aiming\udat developing innovative nanobased coatings with improved Near InfraRed reflecting capabilities. The\udkey idea is to work on a nanoscale by tuning the crystal size and distribution of selected nanostructured\udoxides. Cool prototypes of brown colored ceramic tiles and green acrylic paints have been developed and\udcompared to conventional ones showing an improvement in solar reflectance without any perceptual difference\udin color. The material characterization has been based on the measurement of spectral reflectance\udon a wide wavelength range (300–2200 nm) using a UV/Vis/NIR spectrophotometer. In parallel with the\uddevelopment of nanostructured cool materials, natural aging tests on ceramic and painted concrete tiles\udhave been performed with the goal of identifying and measuring the effects of the main aging factors\udaffecting reflective properties. A significant drop of solar reflectance for paints has been noticed from\udthe very beginning of the testing period while ceramic tiles have confirmed excellent resistance to weathering.\udHowever, both for paints and tiles the effect of soiling cannot be neglected and, if combined to\udweathering, it can lead to a solar reflectance reduction as high as 10%. This preliminary study will pave\udthe way to a future development of dedicated accelerated aging testing procedures for cool materials.