On the Energy Performance of an Innovative Green Roof in the Mediterranean Climate

Luca Evangelisti,Gianluca Grazieschi,Francesco Asdrubali,Marta Roncone,Claudia Guattari

doi:10.3390/en13195163

Abstract

Green roofs have a thermal insulating effect known since ancient times. In the building sector, green roofs represent a sustainable passive solution to obtain energy savings, both during winter and summer. Moreover, they are a natural barrier against noise pollution, reducing sound reflections, and they contribute to clean air and biodiversity in urban areas. In this research, a roof-lawn system was studied through a long experimental campaign. Heat-flow meters, air and surface temperature sensors were used in two buildings characterized by different surrounding conditions, geometries and orientations. In both case studies, the thermal behaviors of the roof-lawn system were compared with the conventional roofs. In addition, a dynamic simulation model was created in order to quantify the effect of this green system on the heating and cooling energy demands. The roof-lawn showed a high thermal inertia, with no overheating during summer, and a high insulating capacity, involving energy savings during winter, and consequently better indoor thermal conditions.

Highlights

Greenhouse gas emissions (GHG), mainly produced by anthropogenic activities, can be considered to be largely responsible for the global average temperature increase, with a growth of about +1 ◦ C compared to the pre-industrial era [1]
In order to provide a clear view of the yearly behaviors of the investigated green roofs, the results are here presented in terms of average data and standard deviations (SDs)
The measurement of the green roof extrados’ temperature and the external surface temperature allowed a preliminary calculation of the roof-lawn thermal conductance, which was equal to 4.487 W/m2 K

Summary

Introduction

Greenhouse gas emissions (GHG), mainly produced by anthropogenic activities, can be considered to be largely responsible for the global average temperature increase, with a growth of about +1 ◦ C compared to the pre-industrial era [1]. It is essential to study UHIs and suggest interventions for the mitigation of these phenomena, thereby reducing their strength [7,8]. Achieving this goal is essential for reducing the growing energy consumption of buildings energy, in particular during summer [9,10,11,12]. The high temperatures in cities during the hottest months can involve significant and negative effects on daily life [13]. One of the most significant solutions for counteract UHIs is represented by green roofs. They are a passive solution characterized by multiple advantages. A green roof generates oxygen, reducing, at the same time, CO2 and Energies 2020, 13, 5163; doi:10.3390/en13195163 www.mdpi.com/journal/energies

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