The evapotranspiration process in green roofs: A review

Abstract

Previous research has shown that most of the green roof benefits are related to the cooling effect. In the literature available, however, it is still not clear how and how much the evapotranspiration affects the performance of a green roof. In order to fill the gap in this research topic, this study carries out a review on the cooling effect due to the evapotranspiration process of green roofs. First of all, an overview of the evapotranspiration phenomenon in green roofs, as well as the equipment and methods used for its measurement are presented. Then, the main experimental results available in literature, the physicalmathematical models and the dynamic simulation software used for the evaluation of the latent heat flux are also analysed and discussed among the available literature. Moreover, this review proposes a classification of the results carried out by previous studies as function of the main parameters affecting the evapotranspiration process (e.g. volumetric water content, stomatal resistance, Leaf Area Index, solar radiation, wind velocity, relative humidity, soil thickness, and substrate composition). Additionally, a sensitivity analysis of the results obtained from the literature allowed underlining the correlation among the main factors affecting the evapotranspiration. Finally, a vision of the world area where green roof studies were performed is provided. From the results, it is possible to emphasize that most of the studies that evaluated the evapotranspiration used high precision load cells. Furthermore, all the heat transfer models of green roofs considered in this review took into account the latent heat flux due to evaporation of water from the substrate and plants transpiration, however, only few of them were experimentally validated.

Green Roof Design: State of the Art on Technology and Materials

“…In addition, the authors also emphasized its performance in reducing stormwater and energy costs, improving air quality, and ecological benefits. Recently, Cascone et al [18] carried out a comprehensive review of the cooling effect, due to the evapotranspiration process, as most of the benefits of green roofs are related to this phenomenon. These previous studies were mainly focused on reviewing the performance and benefits, without providing a description of their technology and materials.…”

The Impact of Green Roofs on the Parameters of the Environment in Urban Areas—Review

“…The proposed research should help to formulate a model defining the following: Reduction of gas and dust pollution, reduction of the urban heat island effect, as well as sustainable rainwater management taking into account the area of green roofs in the city and experimental coefficients determined in the course of the research. Drawing on the findings of various researchers [7,20,21,48,75,[101][102][103], the research should be carried out using geographic information systems (GIS), EnergyPlus software, computational fluid dynamic (CFD) models, and modeling with the use of a neural network.…”

Water Resilience by Centipedegrass Green Roof: A Case Study

“…Water loss on green roofs was mainly driven by plant ET [52]. The more ET water lost, the more water storage space created, which means more water can be retained in the green roof system and the less runoff will be occurred during the next rainfall event [53].…”