Experimental Evaluation and Numerical Simulation of the Thermal Performance of a Green Roof

Claudia Guattari,Francesco Asdrubali,Roberto De Lieto Vollaro,Luca Evangelisti

doi:10.3390/app10051767

Abstract

In the building sector, both passive and active systems are essential for achieving a high-energy performance. Considering passive solutions, green roofs represent a sustainable answer, allowing buildings to reach energy savings, and also reducing the collateral effect of the Urban Heat Island (UHI) phenomenon. In this study, a roof-lawn system was investigated by means of an extended measurement campaign, monitoring the heat transfer across the roof. Heat-flow meters and air- and surface-temperature probes were applied in a real building, in order to compare the performance of the roof-lawn system with a conventional roof. This experimental approach was followed to quantify the different thermal behaviors of the building components. Moreover, an equivalent thermal model of the roof-lawn system was studied, in order to obtain the equivalent thermal properties of the roof, useful for setting building models for yearly energy simulations. The roof-lawn system revealed its advantages, showing a higher thermal inertia with no overheating in summertime and a lower thermal transmittance with energy savings in wintertime, and, consequently, better indoor conditions for the occupants of the building.

Highlights

In recent years, urban areas’ growth and the consequent sources of pollution have led to an increase in terms of global warming
Urban Heat Island (UHI) is represented by the temperature rises in areas characterized by a high urban fabric, if associated to the surrounding rural areas [1]
On the one hand, the internal temperatures of the buildings can be set lower, the same cannot be done for the external environment, with the exception of countermeasures finalized for the reduction in UHI effects

Summary

Introduction

Urban areas’ growth and the consequent sources of pollution have led to an increase in terms of global warming. UHI is represented by the temperature rises in areas characterized by a high urban fabric, if associated to the surrounding rural areas [1]. It is noteworthy to suggest interventions for the mitigation of this phenomenon, lowering its intensity. Achieving this goal is fundamental to reducing the increasing building energy consumption, especially during the warmer months [2,3]. On the one hand, the internal temperatures of the buildings can be set lower, the same cannot be done for the external environment, with the exception of countermeasures finalized for the reduction in UHI effects. The high temperatures that occur in cities during the warmer months can involve substantial and damaging effects on daily life [4–7]

Objectives

Methods

Results