Do green roofs really provide significant energy saving in a Mediterranean climate? Critical evaluation based on different case studies
|نوع نگارش مقاله||
scopus – master journals – JCR
۴٫۲۷۶ در سال ۲۰۲۰
۲۶ در سال ۲۰۲۱
۰٫۹۰۱ در سال ۲۰۲۰
|شاخص Quartile (چارک)||
Q1 در سال ۲۰۲۰
خرید محصول توسط کلیه کارت های شتاب امکان پذیر است و بلافاصله پس از خرید، لینک دانلود محصول در اختیار شما قرار خواهد گرفت و هر گونه فروش در سایت های دیگر قابل پیگیری خواهد بود.
فهرست مطالب مقاله:
Green roofs represent a growing technology that is spreading increasingly and rapidly throughout the building sector. The latest national and international regulations are promoting their application for refurbishments and new buildings to increase the energy effi- ciency of the building stock. In recent years, vegetative coverings have been studied to demon- strate their multiple benefits, such as the reduction of the urban heat island phenomenon and the increase in the albedo of cities. On the contrary, this study aims to verify the actual benefit of applying a green roof on a sloped cover compared with installing a highly insulated tiled roof. The EnergyPlus tool has been used to perform dynamic analyses, which has allowed to understand the behavior of two different stratigraphies in accordance with weather condi- tions, rain, and irrigation profiles. Results have shown that the installation of a green roof cannot always be considered the best solution for reducing building energy consumption, espe- cially if compared with a classic highly insulated clay tile roof. In terms of summer air condi-
tioning, the maximum saving is 0.72 kWh/m2. The presence of water in the soil has also been
proven a crucial factor.
|بخشی از متن مقاله:|
In recent years, new construction techniques have been designed and implemented due to the urgent need to improve the international building stock and reduce the production of CO2 in the atmosphere. Green roofs, also known as eco-roofs, are among these techniques.
Several countries, following the guidelines issued by the
European Parliament via the EPBD (European Parliament,
2010) and its recent amendment (European Parliament,
2018), encourage the efficiency of housing to reach the ambitious levels of nearly zero-energy buildings or even net zero-energy buildings. They adopt a massive policy aimed at refurbishing existing buildings and renovating new buildings with green roofs, without making any wide and relevant implementation (Versini et al., 2020).
In Italy, the Action Plan for the environmental sustain- ability of consumption aims to reduce the environmental impact of new buildings and increase the number of green contracts. Accordingly, the Ministerial Decree (DM) 24/12/
2015 (Ministeroe della Tutela del TerritorioMare, ۲۰۱۶) defined the Minimum Environmental Criteria (CAM in Ital- ian) for the assignment of design services and works for new constructions; the last update, DM ۱۱/۱۰/۲۰۱۷ (Ministero dell’Ambiente e della Tutela del Territorio e del Mare, 2017), specified that the use of green roofs must be preferred for roofing.
Concerning environmental benefits, several studies have demonstrated the benefits that green roofs produce on the ecosystem. In large cities, one of the greatest environ- mental problems is the continuous increase in temperature due to the urban heat island (UHI) phenomenon, which places the most vulnerable groups of the population in danger and amplifies the pollution problems. The use of vegetation above building rooftops is the most useful technology to increase the albedo of cities (Santamouris, 2014; Suter et al., 2017). Bevilacqua et al. (۲۰۱۷) have shown that in a southern Mediterranean climate, a green roof can maintain the surface temperature that is between 57% and ۶۳% lower than that of a traditional roof in June owing to the phenomenon of evapotranspiration. Its func- tion as an air filter has also been demonstrated, with the resulting reduction in pollution (Baik et al., 2012). Versini et al. (۲۰۱۶) have shown that the implementation of a green roof on 100% of a building’s roof results in a decrease between 30% and 60% in water peak discharge, reducing the risk of sewage overflow; a similar result has also been confirmed by Piro et al. (۲۰۱۸), who have detected a retained volume of ۵۷٫۵%. Madre et al. (۲۰۱۴) have also demonstrated the importance of green roofs for wild urban flora, protecting the biodiversity of cities.
The wide optimism and the spread of this technology, supported by various environmental reasons, some of which were previously mentioned, have, however, overlooked the real benefit in reducing building energy demand; depending on climatic conditions, a green roof could be irrelevant or even detrimental (Susca, ۲۰۱۹). Case study results have confirmed that buildings built in accordance with new strict energy regulations, with high levels of insulation, achieve moderate benefits from the use of a green roof rather than a classic well-insulated pitched roof (Gargari et al., 2016a); investigating every parameter of the green roof and analyzing every detail are important. Therefore, every aspect, such as the materials used, stratigraphies, sedum type, and, specially, the building location and climatic conditions, must be considered.
From a life cycle approach (LCA) assessment combining the different factors, as listed previously, with the mod- erate to high maintenance requirements of green roofs, the impact of a green roof does not always differ significantly from that of a traditional roof when it is built using recycled materials (Gargari et al., 2016b).
Various approaches and many studies have been carried out on the thermal performance of green roofs in different locations, with the different aims to validate the results of simulations with physical models (A´vila-Herna´ndez et al.,
2020; Niachou et al., 2001), to apply direct measurements to study the different parameters associated with energy behavior by using scale models (Jiang and Tang, ۲۰۱۷; Collins et al., 2017; Coutts et al., 2013; Lisi et al., 2018; Tan et al., 2017) or real size mookups installed on a rooftop (Bevilacqua et al., ۲۰۲۰; Tang and Zheng, ۲۰۱۹; Porcaro et al., 2019; D’Orazio et al., 2012; Mutani and Marchetti,
2015; Korol and Shushunova, ۲۰۱۶; Tang and Qu, ۲۰۱۶; Silva et al., 2016), or to refine and understand the in- fluences of the parameters of vegetative roofs, such as leaf area index (LAI), soil height, and suitable plant species (Peri et al., 2016; He et al., 2017; Eksi et al., 2017; Zhao et al., 2013).
All building regulations share the widespread optimism about the benefits provided by using green roofs, almost forcing their application; each case should be thoroughly analyzed individually to realize at least an LCA analysis (Antonio et al., 2015; Saiz et al., 2006).
The purpose of this study is to perform hourly dynamic energy simulations during a few significant weeks over the summer and winter seasons of building use. An edifice, built with a green roof or with a classic clay tile roof, has been studied using the high-resolution building energy simulation program EnergyPlus (EP), considering all the parameters influencing the real behavior of the building. Previous studies have mainly involved the energy aspects of two technical solutions, without considering environmental as- pects, such as the reduction of the UHI phenomenon. In this
study, the edifice has been placed and analyzed in three different Italian cities, with three distinctive climatic and meteorological characteristics (solar radiation, rain profile, wind speed, humidity, etc.). Furthermore, different irri- gation profiles have been simulated.
This study may be valuable in enriching the scientific discussion on the use of this particular technology, with quantitative evaluations. The quantitative examples pro- vided in this paper can be a valid indication for those who have to make choices in the early stages of design, opting or not to use green roofs in Mediterranean locations.
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