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.

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.

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 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 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 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 Green Roof Design with Engineered Extensive Substrates and Native Species to Evaluate Stormwater Runoff and Plant Establishment in a Neotropical Mountain Climate

2020 ◽  
Vol 12 (16) ◽  
pp. 6534
Author(s):  
Carlos Vicente Rey ◽  
Natalia Franco ◽  
Gwendolyn Peyre ◽  
Juan Pablo Rodríguez
Keyword(s):  
Native Species ◽  
Green Roof ◽  
Oxygen Demand ◽  
Green Roofs ◽  
Environmental Benefits ◽  
Plant Establishment ◽  
Climate Conditions ◽  
Mountain Climate ◽  
Roof Design ◽  
Selection Of

Green roofs are increasingly being implemented in cities for their multiple environmental benefits. Their optimal design requires an appropriate selection of components, including substrates and plant species, to ensure local sustainability in the long term. The present study seeks to assess the runoff quality and quantity of extensive green roofs located in Bogotá (Colombia). The assessment consists of testing different substrates, designed using locally available constituents and a selection of native species. The best performing substrate mixtures, in terms of runoff volume reduction and plant establishment, were jointly evaluated with three native species (i.e., Paepalanthus alpinus, Achryrocline bogotensis and Echeveria ballsii). On average, engineered substrates presented significantly lower concentrations in several water quality parameters (electric conductivity, total phosphorus, phosphates, Total Kjeldahl Nitrogen, nitrates, nitrites, color, biological oxygen demand and chemical oxygen demand) than the commercial extensive substrate used as control. The species Paepalanthus alpinus and Echeveria ballsii showed significant establishment and were considered potentially suitable species for green roofs in Bogotá. The obtained results, therefore, provide recommendations for green roof design in neotropical mountain climate conditions.

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 Experimental Investigation of Green Roof Impact on Buildings Energy in Hot Climate

2020 ◽  
Vol 13 (2) ◽  
pp. 144-152
Author(s):  
Farah Abdulkadhum Malik ◽  
Alaa Liaq Hashem
Keyword(s):  
Heat Transfer ◽  
Solar Radiation ◽  
Energy Demand ◽  
High Surface ◽  
Green Roof ◽  
Green Roofs ◽  
Ambient Air ◽  
Maximum Temperature ◽  
Flux Flow ◽  
Zone Temperature

Green roofs are a layer that effectively working on blocks of solar radiation from entering the building's structure below partially. Its work as a passive cooling technique, and have the potential to reduce the high surface temperature of conventional roofs because of the soil thermal resistance, evapotranspiration, and several effects for foliage shading. This affects the heat flux flow of the roof that in turn influences the indoor thermal conditions and the building energy demand. The research goals are to test the influence of the green roof on reducing heat transfer to the interior of heavy structural buildings. The experimental part was done to examine the effect of the green roof and compare it with a standard roof under influence of ambient air temperature, solar radiation, and wind speed and test the effect of the green roof on reducing heat transfer inside the building. The model site was at the Diwanyah city (Latitude: 31.9868 and Longitude: 44.9215), the engineering college campus, Qadisiyah University. The experimental setup includes two cubicles, with equal internal volume values (163cm * 163cm * 105cm). The experimental results showed for the period 5-8 September 2019. The maximum zone temperature was 46.4 °C for traditional roof and 37.06 °C for the green roof at 3:24 p.m. The results showed that the maximum internal temperature was 46.97 °C and 36.42 °C for the traditional roof and green roof respectively at 3 p.m. Also,  the results for period 18-21 July 2019 noted that the zone temperature decreased by 7.5 °C and the maximum temperature of the internal traditional standard roof’s surface is 45.66 °C  and 37.41 °C for the green roof.

scholarly journals Influence of environmental factors on retention of extensive green roofs with different substrate composition

2019 ◽  
Vol 86 ◽  
pp. 00026 ◽  
Author(s):  
Anna Baryła ◽  
Agnieszka Karczmarczyk ◽  
Agnieszka Bus ◽  
Edyta Hewelke
Keyword(s):  
Environmental Factors ◽  
Green Infrastructure ◽  
Urban Areas ◽  
Green Roof ◽  
Green Roofs ◽  
Statistical Regression ◽  
Climate Conditions ◽  
Factors Affecting ◽  
Organic Mineral ◽  
Local Ecosystem

Increasing recognition is being given to the adaption of green roofs in urban areas to enhance the local ecosystem. Green roofs may bring several benefits to urban areas including flood mitigation Analysis of environmental factors affecting the outflow of green roofs is the subject of many studies. The work assessed how environmental factors moisture of structural layers and antecedent dry weather period influence the retention on two types of green roof substrates. The monitoring of environmental factors and amount of runoff was carried out on two models of green roofs covered by extensive vegetation (mosssedum-herbs) with substrates of an organic-mineral and mineral composition for 8 months. A statistical regression approach identified potential antecedent meteorological factors and moisture indicators of extensive green-roof retention. Continuous field monitoring data revealed the combined effects of rainfall depth and antecedent dry weather period to explain the measured stormwater retention under a moderate climate conditions regime. It is important to incorporate site-specific planning and assessment prior to green infrastructure design.

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