Cool colored cement-based construction elements for the historical centers: development and thermal-energy performance assessment

Construction elements do not only determine the energy performance of the building itself, but also its appearance. Nowadays, while Architectural expression is still a key decision-driver to select a particular construction element, equal or superior importance is placed on energy performance, towards Urban Heat Island phenomenon mitigation and to reduce energy consumptions. In historical centers both appearance and energy performance are taken into account and here the external layer of the envelope and the visible parts of the building are built with traditional materials and technological solutions. The optimization of the energy performance is achieved by means of internal insulation layers or other active and passive solutions. Efficient materials and construction elements are usually light-colored to reflect the largest part of the solar radiation, while many historical centers are characterized by reddish or grayish colors. Thus, in this study innovative cool colored cement-based mortar materials were developed to overcome this issue. These materials are prepared directly on site, by mixing two types of pigments (white infrared reflective and traditional colored pigments) to achieve the desired color saturation. Then, optic and thermal properties were assessed and yearly dynamic simulations of a historic case study building performed, by comparing traditional colored mortar and the prototype cool mortar envelopes, as well as other passive retrofit solutions. The research demonstrate that such cool colored materials can maintain lower surface temperatures (-8°C), while reducing energy demand for cooling (-3%).