On Innovative Cool-Colored Materials for Building Envelopes: Balancing the Architectural Appearance and the Thermal-Energy Performance in Historical Districts

Abstract

Architectural expression and energy performance are key decision-drivers in the selection of a particular construction element, with the purpose of Urban Heat Island mitigation, energy-consumption reductions, and cultural heritage preservation in historical centers. In historical centers, the external layer of the envelope and the visible parts of the building are built with traditional materials and technological solutions, such as single-layer walls or brickworks, depending on the country's context, while the energy performance is usually optimized by means of internal insulation layers, or other active and passive solutions. Thermal-energy efficient materials and construction elements for the temperate, warm climate of the Mediterranean area are usually light-colored to reflect the largest part of solar radiation, thus reducing energy demands for cooling and improving thermal comfort conditions for occupants. On the other hand, many historical centers in such areas are characterized by reddish or grayish colors. In this work, we considered Italian historical areas, and other countries in the Mediterranean area with present similar situations. Thus, in this study, innovative, cool-colored, cement-based materials were developed to improve the thermal-energy performance of the external envelope of historical/historic built environments, without altering their appearance. These materials were prepared directly on-site, by mixing two types of pigments to achieve the desired color saturation. Optic and thermal properties were assessed, and yearly dynamic simulations of a historic, listed, case study building were performed, by comparing traditional-colored mortar and the prototype cool mortar envelopes. The research demonstrates that such cool-colored materials can maintain lower surface temperatures (−8 • C), while reducing energy demands for cooling (−3%).

A Sustainable Approach towards the Retrofit of the Public Housing Building Stock: Energy-Architectural Experimental and Numerical Analysis

“…The investigation of the energy performance of the proposed passive strategies was carried out in a dynamic regime for an entire year of building use by considering the different solutions of the retrofitted envelope, by following the previous mentioned strategy. The modelling and simulation were carried out with the software DesignBuilder [59], which is widely employed in state-of-the-art research on energy performance [60][61][62] (Figure 4).…”

A Model for External Walls Selection in Hot and Humid Climates

“…Discussing with more detail, architectural design; building form, and openings configuration have a pivotal role in maintaining thermal comfort, benefiting from proper natural ventilation for buildings in hot and humid climate [64][65][66][67]. The lack of building provision with overhang and shading [64] as well as not using light-colored reflective materials in building envelope in order to reject the excessive solar gain in over heated periods [68] are of significant reasons to have discomfort condition within the buildings. Moreover, the HVAC system capacity and the plant function affecting the level of thermal comfort and PMV values while increasing the discomfort hours.…”

Pocket parks for human-centered urban climate change resilience: Microclimate field tests and multi-domain comfort analysis through portable sensing techniques and citizens’ science

“…In the last decade, several contributions have been produced by the scientific community about effective strategies. Among them, the most documented one consist of (i) replacing dark materials with high albedo light colored materials, increasing the albedo of the cities [19][20][21]; (ii) introducing water bodies and water elements [22][23][24]; (iii) increasing urban greenery, i.e. vegetated urban areas and green surfaces [25]; and (iv) increasing thermal energy storage capability [26,27].…”