Optical Characteristics of Traditional Portuguese Azulejos: Mixing Colors to Obtain “Cool” Building Façades

The need to reduce energy consumptions in buildings brings modern research to focus on the use of natural sources. In this context, the interest towards traditional architecture has been fueled, since one of the characteristics identifying it is the intuitive and intrinsic link between the building and the surrounding environment. For example, in Mediterranean traditional buildings the attention to the orientation, the limitation of openings, the use of shading systems, the great thermal inertia of the envelope, the exploitation of natural ventilation and the light colored external coatings are all technical answers to the overheating risks typical of hot climates. In this context, the Portuguese traditional habit to cover building façades in azulejos (square ceramic tiles painted in vivid colors) is undoubtfully an interesting topic. The paper describes optical and chromatic characteristics of four types of azulejos by means of spectral measurements. Obtained results have demonstrated that the chromatic composition of the tiles, despite dark colors are mixed with clear ones, is such to determine visual reflectance values higher than expected. This seems to suggest that, even if the chromatic composition in the past was mostly driven by decorative issues and visual intuitive judgments, the energetic needs were not completely neglected or at least that the traditionally preferred colors were such to obtain a positive effect in enhancing reflected component of daylight. © 2020 The Author(s). Published by solarlits.com. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/).