Analysing the potential of optically enhanced dark-coloured finishing coats for ETICS performance improvement

Nowadays, the construction of new buildings and their renovation must consider thermal requirements, safeguarding the thermal comfort conditions during summer and winter. Inevitably, building envelope systems absorb a large part of the incident solar radiation. ETICS (External Thermal Insulation Composite Systems) have emerged to support building energy efficiency in the construction sector. However, the thermal stress induced by heat accumulation in conventional ETICS results in cracks and microfractures, allowing water penetration and compromising thermal performance. This effect is more pronounced with dark-coloured coatings, which have gained popularity for aesthetic reasons. Although visually appealing, these coatings typically absorb a significant portion of solar radiation, intensifying the thermal stress on the rendering system and leading to subsequent façade degradation. As such, this work aims to address these challenges by incorporating reflective nanomaterials into dark-coloured coatings. The coatings were tailored to enhance the optical properties without compromising the visual aspect. The thermo-optical performance revealed an overall total reflectance increase for the modified dark-coloured finishing coats (15 % and 20 %), compared to just 12 % for the non-modified version, with low colour variation. Additionally, the hygric behaviour of the enhanced solutions was not compromised. Consequently, the thermal oscillation responsible for fractures will be reduced, ultimately contributing to extending the service life of ETICS while promoting sustainable building practices. • The new formulated dark-coloured coats improved the NIR reflectance. • Optical improvements were achieved maintaining aesthetic quality. • CuO/TiO 2 nanocomposite formulation met moisture transport requirements, with low biological colonisation levels.