Passive solutions for building energy efficiency represent an interesting research focus nowadays. In particular, natural materials are widely investigated for their potential intrinsic high thermal energy and environmental performance. In this view, natural stones represent a promising solution as building envelope covering and urban pavement. This paper concerns the experimental characterization of several low-cost and local gravel coverings for roofs and urban paving, properly selected for their natural high albedo characteristics. To this aim, the in-field albedo of gravel samples is measured with varying grain size. These in-field measurements are compared to in-lab measurements of solar reflectance and thermal emissivity. The analysis shows a significant variation of the albedo with varying grain size. Both in-lab and in-field measurements agree that the stones with the finest grain size, i.e., fine sand, have the best optic-thermal performance in terms of solar reflectance (62%). This feature results in the reduction of the surface temperature when exposed to solar radiation. Moreover, a natural mixed stone is compared to the high reflectance stone, demonstrating that the chosen stone presents an intrinsic “cool” behavior. Therefore, this natural, low-cost, durable and sustainable material could be successfully considered as a natural cool roof or cool paving solution.

Local environmental boundaries play an important role in determining microclimate conditions affecting thermal-energy behavior of buildings. In this scenario, the purpose of the present work is to investigate how residential buildings are affected by different local microclimate conditions. To this aim, the continuous microclimate monitoring of (i) a rural area; (ii) a suburban area; and (iii) an urban area is carried out, and the comparative analysis of the different boundary conditions is performed. In particular, the effect of the presence of a large lake in the rural area on building energy demand for heating and cooling is evaluated, both in winter and summer. Coupled degree hour method and numerical analysis are performed in order to predict the energy requirement of buildings subject to local microclimate boundary conditions. The main results show higher air temperature and relative humidity values for the rural area. No significant mitigation effect due to the lake presence is found in urban and suburban areas because of the peculiar wind regime of the region. Additionally, the dynamic thermal-energy simulation shows a decrease of 14% and 25% in the heating consumption and an increase of 58% and 194% in cooling requirements of buildings situated in the rural area around the lake compared to the urban and suburban areas, respectively.

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%).

The sustainability and efficiency of buildings represents a crucial issue since the building sector is currently responsible for more than 40% of energy consumption and emissions. This concern is extended to historical buildings, as they are typically low-performance constructions usually equipped with ineffective systems. For these reasons, the upgrade of historical constructions from an energy and environmental perspective is urgent, especially in those countries where such buildings represent more than half of the building stock. This work concerns the refurbishment of a historical Italian building by integrating passive and active solutions to optimize the indoor thermal comfort and the energy performance. To this aim, the innovative GBC Historic Building^® rating system, a new tool evaluating the sustainability level of conservation-related activities on pre-industrial buildings, is applied. A combined trigeneration heat and power plant with an absorption chiller to produce cooling and powered by vegetable oil is installed in the building. A dynamic simulation of the building is also carried out to predict the post-retrofit energy performance upgrading. The final aim is to propose an integrated approach for the preservation and energy upgrading of existing constructions by improving their energy performance and environmental quality while protecting their heritage value.

The reduction of the energy use of buildings at the urban scale represents a key research and design topic with the purpose of developing specific methods for saving energy in buildings. These methods are often focused on the analysis of building thermal-energy behavior by considering the building as a stand-alone object. In this perspective, the thermal-energy behavior of two buildings in New York City is evaluated in this paper with varying urban contexts, in order to evaluate the Inter-Building Effect (IBE). The IBE analysis shows that the inaccuracy in neglecting the urban context in building modeling varies from 9.6 percent, to 71.9 percent. These results confirm that, in order to make accurate predictions about building thermal-energy performance in real urban contexts through dynamic simulation, the interaction between the building and the urban surrounding should be taken into account, in particular in dense urban areas.

Historical buildings represent one-third of the Italian stock and are often used as museums. Such buildings typically are not equipped with control systems and indoor microclimate does not guarantee a proper conservation of the building finishing and artworks. Additionally, conditions are far from visitors’ ideal indoor air quality (IAQ). This paper proposes a methodology for microclimate analysis that deals with artworks preservation and occupants' conditions optimization. The methodology consists of monitoring and data analysis using non-invasive equipment for the preservation of the building structure, artworks, and occupanst’ IAQ. To this aim, the monitoring of an Italian building was performed. The microclimate was monitored to characterize the environmental quality of the investigated area. Around 60% of the relative humidity values were higher than the target for occupants’ well-being and artworks preservation. Air temperature was stabilized by the thermal mass of the envelope, to reduce winter overcooling risks though. In winter, indeed, up to 40% of temperatures were below the limits for the artworks preservation. The CO₂ level was acceptable as it was always below 1000 ppm. The results showed how a careful control and monitoring protocol is needed when heritage buildings are used for artworks preservation and also with a requirement to meet occupants’ satisfaction targets.