Improving the optical properties of finishing coatings for façade systems

The need to improve energy efficiency of the building stock has led to a continuous increase in the implementation of exterior thermal insulation systems, such as ETICS. Progressively, these systems are being applied with darker colours, increasing the concern for hygrothermal behaviour and durability. Despite the significant developed studies, very few reports regarding their optical properties are available. The optical and catalytic capacity turns nanomaterials into excellent candidates for use in finishing coatings with high solar reflectance with dark colours without affecting the aesthetic characteristics, thus improving the durability of such coatings. Our study targeted the development of innovative envelope systems by increasing their solar reflectance through new finishing coatings formulations with the inclusion of nanoparticles. For that, it is necessary to develop and optimize nanoparticles formulations to achieve a high near-infrared reflectance. Here, we studied how the incorporation of reflective nanomaterials influence the optical behaviour of a black colourant for a finishing coating, varying the concentration in the coating from 0 to 20%. Such optical performance was experimentally evaluated through spectral reflectance calculations using a modular spectrophotometer, which allowed an understanding of the relation between these properties and the morphological and structural characteristics of the nanoparticles. The results from such studies can help formulate new finishing coatings with increased near-infrared reflectance of buildings façades, using, for instance, more than one type of nanoparticle.