Experimental Analysis of Natural Gravel Covering as Cool Roofing and Cool Pavement

Abstract

Abstract: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.

An Insight into the Commercial Viability of Green Roofs in Australia

“…Therefore, it is interpreted that filling the knowledge gap in the area of green roofs enhances the competitive advantage of the technology in the construction market and eventually contributes to extended application. The result of studies on competing technologies, such as cool roofing [60], is a proper benchmarking tool to evaluate the competitiveness of the green roof against other advanced building technologies, particularly in regards to thermal insulation and energy performance. Pisello et al [61] suggest that a combination of the two aforementioned technologies, the cool-green roof, is a promising solution where other invasive mitigation strategies are not practical to address the urban heat island phenomenon.…”

Evaluation of Different Urban Microclimate Mitigation Strategies through a PMV Analysis

“…This is why urban areas must be planned by implementing, where necessary, proper mitigation strategies. Some of these strategies, partially affecting each other, are: the use of high albedo surfaces [26][27][28][29][30], evaporation from porous surfaces [31,32], evaporation from ground-level water surfaces [33] and roof ponds [34], vegetated surfaces [35], rooftop gardens [36][37][38][39][40], and trees [27,41]. This paper, through the examination of a case study concerning the Cloister of San Pietro in Vincoli (placed right inside the Faculty of Engineering of the Sapienza University of Rome), evaluates how some of the mitigation strategies previously mentioned affect the microclimate and the outdoor thermal comfort.…”

Highly Reflective Roofing Sheets Installed on a School Building to Mitigate the Urban Heat Island Effect in Osaka

“…Pisello et al [10] carried out an experimental characterization and optimization of a new membrane for building roofs with the aim of contributing to the reduction of the peak ambient temperatures and improvement of the intense UHI phenomenon during summer. Additionally, the in-field and in-lab measurements of several low-cost natural gravel coverings have also been implemented to counter the UHI phenomenon by Pisello et al [11]. Gobakis et al [12] developed a number of inorganic coatings both for buildings and urban environments, and the materials were characterized using X-ray diffraction (XRD) and differential thermal analysis (DTA) to verify their composition, and the optical properties of these materials were analyzed by measuring the surface temperature while exposed to the outdoor environment.…”

“…Among the strategies of UHI mitigation and building energy conservation, HR materials used for roof or pavement have been developed and researched widely [10][11][12]. Pisello et al [10] carried out an experimental characterization and optimization of a new membrane for building roofs with the aim of contributing to the reduction of the peak ambient temperatures and improvement of the intense UHI phenomenon during summer.…”