Optothermal properties of façade coatings: Effects of environmental exposure over solar reflective index

Abstract

The materials that compose the urban envelope are determinant for the reduction of heat gains and overheating of a city. Increasing the solar reflection of vertical materials is an efficient strategy to reduce urban temperatures. In this context, this work evaluates the aging effect on the optothermal performance of 96 commonly used textured claddings and façade paints in the local building park over a three-year period. The goal is to establish the influence of morphological characteristics such as color, composition, finishing and texture on the thermal behavior and aging response of the façade paints and textured claddings previously mentioned, to establish a relationship between the features of façade materials and their capacity to mitigate urban warming. The impact of aging, which was quantified by the modification of the Solar Reflectance Index (SRI), showed that color and finish are the main morphological characteristics that affect the materials’ thermal behavior. Although textured coatings have higher initial SRI values, they registered a stronger degradation over time in opposition to façade paints which remained more stable to aging. In other words, façade paints are a more efficient cooling strategy than textured coatings. After three years, the surface temperature increases up to 30 °C in coatings and up to 16.5 °C in paints.