scholarly journals Hydrological Behaviour of Extensive Green Roofs with Native Plants in the Humid Subtropical Climate Context

Water ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 44
Author(s):  
Lucia Bortolini ◽  
Francesco Bettella ◽  
Giampaolo Zanin
Keyword(s):  
Green Roof ◽  
Green Roofs ◽  
Mitigation Measures ◽  
Subtropical Climate ◽  
Native Plant ◽  
Mineral Layer ◽  
Climate Conditions ◽  
Relative Contribution ◽  
Good Ability ◽  
Valid Solution

Different mitigation measures with vegetation have been proposed to sustainably manage rainwater, among which green roofs have demonstrated to be a valid solution in urbanized areas. Green roofs have gained interest also in Italy, but their spreading is generally based on application of ready-to-use packages, poorly tested in the specific climate conditions. A study was carried out to evaluate the green roof solution most suitable in the humid, subtropical climate context of Veneto Plain (north-eastern Italy) to reduce outflow volumes from building roofs into the urban drainage systems. Twelve different microcosm combinations of extensive green roof (three plant mixtures × two substrates × two storage/drainage layers) were tested and compared with gravel (considered as a conventional flat roof with gravel ballast). The tested drainage/storage layers were a preformed layer in recycled HDPE (PL) and an expanded perlite mineral layer (ML), and the growth medium layers were recycled brick substrate (RS) and volcanic substrate (VS). Three different mixtures of native plant species were transplanted: Sedum (SE), herbaceous perennial (HE), and suffruticose (SF). Results showed that all the green roof systems have a good ability to manage rainwater, with a retention ranging on average from 46.2% (SE-RS-PL microcosms) to 62.9% (SF-RS-ML microcosms) of the precipitation in the two-year period (September 2014–August 2016), against 15.4%, retained by gravel. Over the two-year period, the retained rainfall volumes were about 100% for all the light rainy events (<10 mm) and varied within a range of 48–95% for medium rainy events (≥10 and <25 mm) and 20–88% for heavy rainy events (≥25 mm), depending on rainfall depth and the antecedent weather period. The layer that gave the highest relative contribution to the stormwater retention was the vegetation layer, followed by the drainage/storage layers and then the substrate layer. In particular, SF plants decreased the outflows by 15.2% on average compared to SE, and ML layer retained more than 10% of precipitation compared to PL layer. At last, the analysis of variance showed that, within each layer, the more effective in water retention, able to generate less outflow volumes, was similarly suffruticose and herbaceous mixtures, the crushed bricks substrate, and the mineral drainage/storage layer.

scholarly journals Performance of Three Different Native Plant Mixtures for Extensive Green Roofs in a Humid Subtropical Climate Context

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3484 ◽  
Author(s):  
Giampaolo Zanin ◽  
Lucia Bortolini
Keyword(s):  
Canopy Cover ◽  
Crop Coefficient ◽  
Green Roofs ◽  
Subtropical Climate ◽  
Native Plant ◽  
Mineral Layer ◽  
Climate Conditions ◽  
Extensive Green Roofs ◽  
Stormwater Retention ◽  
Vegetation Layer

Most of the services and benefits of green roofs are related to the substrate as well as the vegetation layer. Although plant selection should be made on the basis of green roof typology, morphology, and climate conditions, very often, Sedum species only are used worldwide. However, they do not always guarantee the best performances; hence, it is important to investigate different plant species and their performance in different climate contexts. Herein, an experiment was conducted using three plant mixes (i.e., a Sedum mix, a perennial herbaceous mix, and a suffruticose mix), grown in boxes containing two substrates (a volcanic substrate or a recycled crushed brick substrate) and two drainage/storage layers (a preformed layer or a mineral layer), in factorial combination. The Sedum mix showed a high canopy cover, comparable to or even higher than that of the other mixes, particularly when supplemental irrigation was stopped. However, the actual crop coefficient (Kcact) of the herbaceous and suffruticose mixes was often higher than that of the Sedum mix. The results also showed that both the substrate and the drainage/storage layer may improve Kcact values as a consequence of their capacity for stormwater retention.

scholarly journals Modeling Green Roof Potential to Mitigate Urban Flooding in a Chinese City

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2082 ◽  
Author(s):  
Li Liu ◽  
Liwei Sun ◽  
Jie Niu ◽  
William J. Riley
Keyword(s):  
Green Roof ◽  
Water System ◽  
Green Roofs ◽  
Subtropical Climate ◽  
Urban Flooding ◽  
Climate Conditions ◽  
Roof System ◽  
Groundwater Levels ◽  
Rain Season ◽  
Peak Runoff

The Middle and Lower Reaches of the Yangtze River (MLRYR) region, which has humid subtropical climate conditions and unique plum rain season, is characterized by a simultaneous high-frequency urban flooding and reduction in groundwater levels. Retrofitting the existing buildings into green roofs is a promising approach to combat urban flooding, especially for a densely developed city. Here, the application potential of the Green Roof System (GRS) and the Improved Green Roof System (IGRS) designed to divert overflowing water from green roofs to recharge groundwater were analyzed in a densely developed city, Nanchang, China. For the first time, the influence of GRS on the hydraulic condition of Combined Sewage System/Storm Water System (CSS/SWS) is analyzed, which is a direct reflection of the effect of GRS on alleviating urban flooding. The simulation results show that GRS can retain about 41–75% of precipitation in a 2-hour timescale and the flooding volumes in the GRS/IGRS region are 82% and 28% less than those of the Traditional Roof System (TRS) in 10- and 100-yr precipitation events, respectively. In the continuous simulations, GRS also enhances Evapotranspiration (ET), which accounts for 39% of annual precipitation, so that reduces the cumulative surface runoff. Considering the IGRS can provide more hydrological benefits than the GRS under the same climate conditions, we may conclude that the widespread implementation of both the GRS and the IGRS in Nanchang and other densely developed cities in the MLRYR region could significantly reduce surface and peak runoff rates.

scholarly journals Green Roof Design Techniques to Improve Water Use under Mediterranean Conditions

Urban Science ◽  
2019 ◽  
Vol 3 (1) ◽  
pp. 14 ◽  
Author(s):  
Teresa Paço ◽  
Ricardo Cruz de Carvalho ◽  
Pedro Arsénio ◽  
Diana Martins
Keyword(s):  
Water Use ◽  
Green Roof ◽  
Green Roofs ◽  
Climatic Conditions ◽  
Native Plant ◽  
Additional Energy ◽  
Climate Conditions ◽  
Native Plant Species ◽  
Roof Design ◽  
Mediterranean Conditions

Green roof typology can vary depending on buildings structure, climate conditions, substrate, and plants used. In regions with hot and dry summers, such as the Mediterranean region, irrigation plays an essential role, as the highest temperatures occur during the driest period of the year. Irrigation might reduce the heat island effect and improve the cooling of buildings during this period, however, the added cost of maintenance operations and additional energy consumption could outrun the benefits provided by the project. Moreover, in situations where water is scarce or primarily channelled to other uses (e.g., domestic, agriculture or industry) during drought occurrence, it is advisable to implement green roof projects with the lowest use of water possible. The objective of the present work is to investigate solutions to optimize water use in green roofs under Mediterranean conditions, such as those of southern Europe. Two case studies are presented for Portugal, and potential techniques to reduce irrigation requirements in green roofs were tested. These addressed the use of native plant species, including the extreme type of a non-irrigated green roof (Biocrust roof) and techniques for plant installation. Plant drought tolerance was found to be an advantage in green roofs under these climatic conditions and, for the species studied, aesthetic value could be maintained when irrigation decreased.

scholarly journals Growth of Native Aromatic Xerophytes in an Extensive Mediterranean Green Roof as Affected by Substrate Type and Depth and Irrigation Frequency

HortScience ◽  
2013 ◽  
Vol 48 (10) ◽  
pp. 1327-1333 ◽  
Author(s):  
Maria Papafotiou ◽  
Niki Pergialioti ◽  
Lamprini Tassoula ◽  
Ioannis Massas ◽  
Georgios Kargas
Keyword(s):  
Plant Growth ◽  
Plant Species ◽  
Green Roof ◽  
Green Roofs ◽  
Native Plant ◽  
Substrate Type ◽  
Irrigation Frequency ◽  
Artemisia Absinthium ◽  
Grape Marc ◽  
Local Character

Green roofs could be a way to increase vegetation in the center of old Mediterranean cities. The need for conservation of local character and biodiversity requires the use of native plant species, whereas the deficiency of water, particularly in semiarid regions, requires the use of species with reduced irrigation needs. Moreover, the aged buildings lead to the use of lightweight green roof constructions. Therefore, research was undertaken to investigate the possibility of using three Mediterranean aromatic xerophytes, Artemisia absinthium L., Helichrysum italicum Roth., and H. orientale L., at an extensive green roof in Athens, Greece. Simultaneously, the possibility of using locally produced grape marc compost was investigated. Substrate type and depth and irrigation frequency effects on growth of these species were studied. Rooted cuttings were planted mid-May in plastic containers with a green roof infrastructure fitted (moisture retention and protection of the insulation mat, drainage layer, and filter sheet) and placed on a fully exposed third floor flat roof at the Agricultural University of Athens. Two types of substrates were used, grape marc compost:soil:perlite (2:3:5, v/v) and peat:soil:perlite (2:3:5, v/v, as a control), as well as two substrate depths, 7.5 (shallow) and 15 cm (deep), and two irrigation frequencies, sparse (5 or 7 days in shallow and deep substrate, respectively) and normal (3 or 5 days in shallow and deep substrate, respectively). Increased contents of macroelements, total phosphorus (P) and potassium (K) in particular, were recorded in the compost-amended substrate, whereas both substrates had similar physical properties. Plant growth was recorded from May to October. The deep compost-amended substrate, independent of irrigation frequency, resulted in taller plants with bigger diameter and aboveground dry weight in all species. However, a remarkable result was that shallow compost-amended substrate with sparse irrigation resulted in similar or even bigger plant growth of all plant species compared with deep peat-amended substrate with normal irrigation. Thus, all three species were found suitable for use in Mediterranean extensive or semi-intensive green roofs, whereas the use of grape marc compost in the substrate allowed for less water consumption and the reduction of substrate depth without restriction of plant growth at the establishment phase and the first period of drought.

Simulation of Thin Green Roof for Summer in Seoul

2017 ◽  
Vol 25 (04) ◽  
pp. 1750034 ◽  
Author(s):  
K. H. Byun
Keyword(s):  
Numerical Analysis ◽  
Simple Model ◽  
Green Roof ◽  
Experimental Studies ◽  
Green Roofs ◽  
Weather Data ◽  
Climate Conditions ◽  
Four Seasons ◽  
Planning Experiment ◽  
Insulation Status

The purpose of this paper is to simulate the performance of thin green roofs during summer in Seoul, where there are four seasons. Many experimental studies are available for the green roofs, but there have not been many analytical studies. Numerical analysis is applied to a simple model developed for this study. The effects of the parameters affecting green roof performance are studied using several roof types. The weather data from Korea Meteorological Administration for the summer in Seoul have been used as an input for the simulation model. The results agree with the trends reported in previous studies. The importance of insulation status of the roof before applying green roof and the climate conditions is confirmed. Analysis such as this paper is necessary and useful before applying green roof or planning experiment on green roof.

scholarly journals Establishment and Persistence of Sedum spp. and Native Taxa for Green Roof Applications

HortScience ◽  
2005 ◽  
Vol 40 (2) ◽  
pp. 391-396 ◽  
Author(s):  
Michael A. Monterusso ◽  
D. Bradley Rowe ◽  
Clayton L. Rugh
Keyword(s):  
Native Species ◽  
Green Roof ◽  
Green Roofs ◽  
Geographic Area ◽  
Michigan State University ◽  
State University ◽  
Native Plant ◽  
Visual Appearance ◽  
Extensive Green Roofs ◽  
The U.S

Although the economic, environmental, and aesthetic benefits of green roofs have been recognized for decades, research quantifying these benefits has been limited—particularly in the U.S. Green roof usage and research is most prevalent in Germany, but can also be seen in several other European countries and Canada. If green roof installations are to be successful in Michigan and the rest of the U.S., then a better understanding of what specific taxa will survive and thrive under harsh rooftop conditions in this geographic area is required. Nine simulated rooftop platforms containing three commercially available drainage systems were installed at Michigan State University. Eighteen Michigan native plants planted as plugs and nine Sedum spp. planted as either seed or plugs were evaluated over three years for growth, survival during both establishment and overwintering, and visual appearance. All Sedum spp. tested were found to be suitable for use on Midwestern green roofs. Of the eighteen native plant taxa tested, Allium cernuum L., Coreopsis lanceolata L., Opuntia humifosa Raf., and Tradescantia ohiensis L. are suitable for use on unirrigated extensive green roofs in Michigan. If irrigation is available, then other native species are potential selections.

scholarly journals A Comparison between Conceptual and Physically Based Models in Predicting the Hydrological Behavior of Green Roofs

Proceedings ◽  
2019 ◽  
Vol 48 (1) ◽  
pp. 8
Author(s):  
Mirka Mobilia ◽  
Antonia Longobardi
Keyword(s):  
Urban Areas ◽  
Goodness Of Fit ◽  
Green Roof ◽  
Green Roofs ◽  
Storm Events ◽  
Climate Conditions ◽  
Hourly Data ◽  
Test Beds ◽  
Fit Indexes ◽  
Flooding Risk

The evolving climate conditions contribute to increase flooding risk in urban areas. Green roofs are effective tools for controlling and managing stormwater runoff. With the aim to prevent these damaging events, an accurate modelling of the response of green roofs to storm events becomes essential. The goal of this research is to compare the accuracy of two hydrological models in predicting the behavior of two green roof test beds in terms of runoff production. The test beds are located in the campus of University of Salerno, in a typical Mediterranean climate and they differ in the composition of the drainage layer. The selected models are the Storm Water management model (SWMM) model and the Nash model. They have been calibrated against hourly data of 25 rainfall-runoff events observed at the experimental site and compared using a number of goodness of fit indexes. The Nash cascade model aims to be a very simple but effective approach. No substantial differences were observed in the behavior of the two green roof plots, though they differ in their design characteristics. Finally, the existence of a relationship between the errors and the rainfall characteristics has been found.

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

2019 ◽  
Vol 11 (11) ◽  
pp. 3020 ◽  
Author(s):  
Stefano Cascone
Keyword(s):  
State Of The Art ◽  
Green Roof ◽  
Green Roofs ◽  
Future Research ◽  
Climate Conditions ◽  
Drainage Layers ◽  
Innovative Materials ◽  
Protection Filter ◽  
Roof Design ◽  
Selection Of

In order to consider green roofs as an environmentally friendly technology, the selection of efficient and sustainable components is extremely important. Previous review papers have mainly focused on the performance and advantages of green roofs. The objective of this paper is to examine the primary layers: The waterproof and anti-root membranes; the protection, filter, and drainage layers; the substrate; and the vegetation. First, the history, modern applications, benefits and classification are analyzed in order to present a well-defined state of the art of this technology. Then, the roles, requirements, characteristics, and materials are assessed for each green roof layers. This technology was compared to a conventional roof technology, Mediterranean climate conditions and their influence on green roof design were assessed, also comparing them with Tropical area and focusing on irrigation systems, examples about the commercial materials and products available in the market were provided and innovative materials coming from recycled sources were analyzed. Future research should evaluate new materials for green roof technologies, in order to enhance their performance and increase their sustainability. The information provided in this review paper will be useful to develop Mediterranean green roof guidelines for selecting suitable components and materials during the design and installation phases.

scholarly journals Mediterranean Green Roof Simulation in Caldes de Montbui (Barcelona): Thermal and Hydrological Performance Test of Frankenia laevis L., Dymondia margaretae Compton and Iris lutescens Lam

2018 ◽  
Vol 8 (12) ◽  
pp. 2497 ◽  
Author(s):  
Antonio Vestrella ◽  
Carmen Biel ◽  
Robert Savè ◽  
Flavia Bartoli
Keyword(s):  
Mediterranean Climate ◽  
Performance Test ◽  
Slow Growth ◽  
Green Roof ◽  
Green Roofs ◽  
Influential Factors ◽  
Energy Costs ◽  
Climate Conditions ◽  
Green Cover ◽  
The Relationship

Green roofs provide a number of environmental advantages like increasing urban biodiversity, reducing pollution, easing burdens on drainage systems, and lowering energy costs thanks to thermal insulation. Frankenia laevis, Dymondia margaretae and Iris lutescens were tested in a green roof installation. For all three species, we assessed two minimal irrigation treatments and one rain-fed treatment to resemble Mediterranean climate conditions analyzing the thermal and hydrological performance of all three species and their substrates through an evaluation of green cover, mortality, and biomass. The most influential factors registered for all three species are the relationship between air and water in the substrate and the interaction between green cover and substrate, respectively, for summer and winter seasons. In particular, D. margaretae preserved more water in its substrate than the other species both in summer and winter and after each rainfall event. F. laevis registered the highest level of variation in terms of substrate water content and of rainwater retention. I. lutescens achieved low hydrological performance, a limited amount of green cover, and slow growth. Our results suggest the absolute need of additional irrigation, managed in accordance with specific functional objectives, for all three species analyzed under Mediterranean conditions and different water regime.

scholarly journals A multi-year comparative analysis of green and conventional roof thermal performance under temperate climate conditions

2021 ◽  
Vol 2069 (1) ◽  
pp. 012067
Author(s):  
P Gunn ◽  
H B Gunay ◽  
P J Van Geel
Keyword(s):  
Comparative Analysis ◽  
Heat Exchange ◽  
Solar Radiation ◽  
Green Roof ◽  
Green Roofs ◽  
Temperate Climate ◽  
Comparative Performance ◽  
Climate Conditions ◽  
Thermal Transmittance ◽  
Radiation Data

Abstract Research suggests that—relative to conventional roofs—green roofs can significantly reduce rooftop heat exchange in moderate climates; however, limited research exists on the performance of green roofs in colder climates. This paper analyzes the comparative performance of two side-by-side roof assemblies: a conventional roof and a green roof located in the temperate climate of Ottawa, Canada. Using two years’ worth of temperature and solar radiation data, we analyze variations in the incremental thermal benefit of the green roof relative to the conventional roof. We discuss factors contributing to these variations, such as precipitation and ambient temperature. Our results indicate that the green roof under investigation reduced thermal transmittance by 31.5% on average across two years. Although the percent benefits were much higher during the summer months, reductions in thermal transmittance were consistently above 7.7% throughout both years, indicating green roofs may be an appropriate alternative to conventional roofs in climates with hot, humid summers and cold, snowy winters.

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