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Chi Yung Jim - One of the best experts on this subject based on the ideXlab platform.
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economic evaluation of Green Roof environmental benefits in the context of climate change the case of hong kong
Urban Forestry & Urban Greening, 2015Co-Authors: Lilliana L H Peng, Chi Yung JimAbstract:a b s t r a c t Green Roof offers multiple environmental benefits to urban ecosystems. Some of these benefits can aid cities in addressing global and local climate-change challenges. Many studies have attempted to convert a wide variety of Green-Roof benefits into economic values but few of them focused on climate-change aspects. This study assessed and valued six climate-related benefits in the compact city of Hong Kong based on localized experimental and modeling studies. The six benefits are thermal insulation, urban heat island (UHI) mitigation, avoided upstream emissions of carbon dioxide (CO2) and air pollutants, CO2 sequestration and air pollutants removal. Two Roof Greening scenarios, extensive (EGR) and inten- sive (IGR), were evaluated for their annual benefits and lifecycle cost-effectiveness under district-scale installation. Results suggest that large-scale Green-Roof installation can substantially reduce energy con- sumption, upstream emission and atmospheric concentration of CO2. Establishment of EGR in the study district Yau Tim Mong (YTM) has an annual total value of USD 12.98 million with unit value of USD 10.77 m −2 of Green Roof, and IGR, USD 22.02 million with unit value of USD 18.33 m −2 . EGR is more economically attractive than IGR in terms of benefit-cost ratio (BCR) and payback period. The 40-year lifecycle BCR of EGR is 3.84 with a payback period of 6.8 years, while the equivalent values for IGR are 1.63 and 19.5 years, respectively. The study suggests a better integration of Green Roof into the current policy schemes in Hong Kong to combat climate change due to the notable benefits and cost-effective characteristics.
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quantitative hydrologic performance of extensive Green Roof under humid tropical rainfall regime
Ecological Engineering, 2014Co-Authors: Gwendolyn K L Wong, Chi Yung JimAbstract:Abstract Urbanization replaces permeable surfaces with relatively impervious ones to intensify mass and temporal response of stormwater runoff. Under heavy rainfalls, urban runoff could impose tremendous stress on the drainage systems, contributing to combined sewer overflow and flooding. Green Roof offers an on-site source-reduction sustainable stormwater management measure that mimics pre-development hydrologic functions. It can retain and detain stormwater as well as delay and suppress peak discharge. However, previous studies were conducted mainly outside the tropics. Since Green-Roof hydrologic performance can be notably influenced by local meteorological conditions, dedicated investigation in the tropics are necessary. Moreover, substrate depth has long been regarded as an influential factor in Green-Roof stormwater retention, but recent findings have implicated that such relationship may be more complex. This study (1) evaluates Green Roof stormwater mitigation performance and potentials in humid-subtropical Hong Kong; and (2) investigates systematically the effect of substrate depth and addition of rockwool, a high water-retention growth medium, on quantitative performance. Using multiple 1.1-m2 raised Green-Roof platforms placed on an urban Rooftop, the effect of four substrate-depth treatments on stormwater mitigation performance was examined over a 10-month study period. The results show that, while the retention under Hong Kong's frequent and heavy rainfall regime seems to be less effective, remarkable peak reduction and peak delay were evidently expressed even when the Green-Roof systems have reached full moisture-storage capacity. No statistical significance was found between treatments, despite the slightly higher mean performance of the 80-mm soil substrate. Satisfactory peak performance of the 40-mm soil substrate implies that a thin substrate can provide effective peak mitigation, especially if building loads are of concern. Extensive Green Roof remains as a promising alternative mitigation strategy to urban stormwater management in Hong Kong with potential application to other tropical areas.
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Green Roof effects on neighborhood microclimate and human thermal sensation
Energies, 2013Co-Authors: Lilliana L H Peng, Chi Yung JimAbstract:Green Roofs have been recognized as an effective sustainable design tool to mitigate urban heat island (UHI) effects. Previous studies have identified Green-Roof benefits in cooling and energy-conservation at the building scale, with limited exploration of the wider influence on neighborhood microclimate and human thermal comfort (HTC). This paper investigated the impacts of community-scale Green-Roof installation on air temperature and HTC in five typical residential neighborhoods of subtropical Hong Kong. The microclimate models ENVI-met and RayMan permitted studies of two main Green-Roof scenarios, namely extensive (EGR) and intensive (IGR). Microclimatic monitoring data from a local experimental Green-Roof site validated the modeling methods. The results verified that Green-Roof cooling effects were not restricted to Rooftops, but extended to the ground to improve neighborhood microclimate. EGR reduced pedestrian-level air temperature by 0.4-0.7 °C, and IGR by 0.5-1.7 °C, with maximum effect in open-set low rise sites. Coverage by building footprints and building height dampened lateral and vertical advection of cool air generated by Green Roofs. Roof Greening also improved notably the Rooftop-podium level HTC. Diurnal duration of high heat stress was reduced by 6-9 h for EGR scenarios, and 9-11 h for IGR. The findings indicated that large-scale Green-Roof installation could bring neighborhood-wide cooling, mitigate urban heat island effect, and furnish more comfortable thermal environment for urban residents.
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weather effect on thermal and energy performance of an extensive tropical Green Roof
Urban Forestry & Urban Greening, 2012Co-Authors: Chi Yung Jim, Lilliana L H PengAbstract:Abstract This study investigated the weather effect on thermal performance of a retrofitted extensive Green Roof on a railway station in humid-subtropical Hong Kong. Absolute and relative (reduction magnitude) ambient and surface temperatures recorded for two years were compared amongst antecedent bare Roof, Green Roof, and control bare Roof. The impacts of solar radiation, relative humidity, soil moisture and wind speed were explored. The holistic Green-Roof effect reduced daily maximum tile surface temperature by 5.2 °C and air temperature at 10 cm height by 0.7 °C, with no significant effect at 160 cm. Green-Roof passive cooling was enhanced by high solar radiation and low relative humidity typical of sunny summer days. High soil moisture supplemented by irrigation lowered air and vegetation surface temperature, and dampened diurnal temperature fluctuations. High wind speed increased evapotranspiration cooling of Green Roof, but concurrently cooled bare Roof. Heat flux through Green Roof was also weather-dependent, with less heat gain and more heat loss on sunny days, but notable decline in both attributes on cloudy days. On rainy days, Green Roof assumed the energy conservation role with slight increase instead of reduction in cooling load. Daily cooling load was 0.9 kWh m−2 and 0.57 kWh m−2, respectively for sunny and cloudy summer days, with negligible effect on rainy days. The 484 m2 Green Roof brought potential air-conditioning energy saving of 2.80 × 104 kWh each summer, equivalent to electricity tariff saving of HK$2.56 × 104 and upstream avoidance of CO2 emission of 27.02 t at the power plant. The long-term environmental and energy benefits could justify the cost of Green Roof installation on public buildings.
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biophysical properties and thermal performance of an intensive Green Roof
Building and Environment, 2011Co-Authors: Chi Yung Jim, S W TsangAbstract:Abstract Green Roofs have been increasingly enlisted to alleviate urban environmental problems associated with urban heat island effect and stormwater quantity and quality. Most studies focus on extensive Green Roofs, with inadequate assessment of the complex intensive type, subtropical region, and thermal insulation effect. This study examines the physical properties, biological processes, and thermal insulation performance of an intensive Green Roof through four seasons. An experimental woodland installed on a Hong Kong building Rooftop was equipped with environmental sensors to monitor microclimatic and soil parameters. The excellent thermal performance of the intensive Green Roof is verified. Even though our site has a 100 cm thick soil to support tree growth, we found that a thin soil layer of 10 cm is sufficient to reduce heat penetration into building. Seasonal weather variations notably control transpiration and associated cooling effect. The tree canopy reduces solar radiation reaching the soil surface, but the trapped air increases air temperature near the soil surface. The substrate operates an effective heat sink to dampen temperature fluctuations. In winter, the subtropical Green Roof triggers notable heat loss from the substrate into the ambient air, and draws heat upwards from warmer indoor air to increase energy consumption to warm indoor air. This finding deviates from temperate latitude studies. The results offer hints to optimize the design and thermal performance of intensive Green Roofs.
David J Sailor - One of the best experts on this subject based on the ideXlab platform.
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experimental and numerical investigation of urban street canyons to evaluate the impact of Green Roof inside and outside buildings
Applied Energy, 2014Co-Authors: Salah-eddine Ouldboukhitine, Rafik Belarbi, David J SailorAbstract:Abstract In the present work, an experimental urban canyon (scale 1:10) with 4 cm concrete wall thickness and full scale Green Roof was used to evaluate the impact of Green Roof inside and outside the buildings. The platform was equally used to validate a coupled heat and mass transfer model for Green Roof behavior. The albedo of the Green Roof was measured and implemented in the numerical model. The developed model has been coupled to a building thermal code (TRNSYS). Then, simulations were conducted for the experimental urban canyon studied where a comparison was undertaken between Green and conventional Roofing. A reduction of the maximum Roof surface temperature by 20 °C was found in summer due to the Green Roof. Green Roof protects the Roof membrane from high temperature fluctuations increasing the Roof longevity and delay the timing of the peak membrane surface temperature by several hours. Also, the presence of vegetation permits to reduce the outside air temperature of the street canyon by 0.8 °C. Hence, Green Roofing is an effective solution to reduce the total energy demand and to improve the urban microclimate in the street canyon for an oceanic temperate climate.
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development and application of a building energy performance metric for Green Roof systems
Energy and Buildings, 2013Co-Authors: Seth Sinclair Moody, David J SailorAbstract:Abstract This study develops a thermal performance metric for vegetated Roof systems. The Dynamic Benefit of Green Roofs (DBGR) is the ratio of Heating, Ventilation and Air-Conditioning (HVAC) energy use for a building with a conventional Roof to that of a building with a Green Roof. If the Green Roof results in lower energy use than a conventional Roof with the same level of thermal resistance the value of DBGR is greater than unity. Data from a field study in Portland Oregon were used to validate the Green Roof model incorporated within a whole-building energy simulation program. This model was then used to estimate the DBGR for a new construction office building in four climates: Portland, Oregon; Chicago, Illinois; Atlanta, Georgia; and Houston, Texas. Results suggest that a Green Roof in Atlanta and Houston would provide net annual HVAC energy savings compared with a traditional Roof. The Chicago case, with severe winter and mild spring/summer/fall, resulted in a smaller energy savings. The DBGR for Portland was less than unity, suggesting a net energy consumption penalty associated with the Green Roof. This was due, in part, to the undesirable evaporative cooling in the shoulder seasons which led to increased building heating loads.
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an updated and expanded set of thermal property data for Green Roof growing media
Energy and Buildings, 2011Co-Authors: David J Sailor, M HagosAbstract:Abstract Vegetated (Green) Roofs alter the Roof surface energy balance and hence affect both building energy consumption and the transport of heat into the environment. Quantitative evaluation of the energetics of Green Roof systems requires accurate knowledge of the moisture-dependent thermal properties of the growing media. To support this need for data and to supplement previously published data we conducted a laboratory study to measure thermal conductivity, volumetric heat capacity, and thermal diffusivity of 12 Green Roof soil samples of varying composition. The results indicate that thermal properties vary significantly as a function of growing media design. Growing media incorporating expanded slate as their aggregate had thermal conductivities that were two to three times those of media that used a porous silica-based aggregate. Media incorporating expanded clay as the aggregate had thermal conductivities roughly in the middle of these extremes. In general the thermal conductivity nearly tripled as the growing media moisture levels were increased from relatively dry to saturated. Also, it was found that compaction typical of Green Roof systems that have been installed for multiple seasons can increase thermal conductivity of moist soils by 30–40% over their uncompressed values.
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a Green Roof model for building energy simulation programs
Energy and Buildings, 2008Co-Authors: David J SailorAbstract:Abstract A physically based model of the energy balance of a vegetated Rooftop has been developed and integrated into the EnergyPlus building energy simulation program. This Green Roof module allows the energy modeler to explore Green Roof design options including growing media thermal properties and depth, and vegetation characteristics such as plant type, height and leaf area index. The model has been tested successfully using observations from a monitored Green Roof in Florida. A preliminary set of parametric tests has been conducted on prototypical 4000 m2 office buildings in Chicago IL and Houston TX. These tests focus on evaluating the role of growing media depth, irrigation, and vegetation density (leaf area index) on both natural gas and electricity consumption. Building energy consumption was found to vary significantly in response to variations in these parameters. Further, this response depended significantly on building location (climate). Hence, it is evident that the Green Roof simulation tool presented here can serve a valuable role in informing Green Roof design decisions.
Jeffrey A Andresen - One of the best experts on this subject based on the ideXlab platform.
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seasonal heat flux properties of an extensive Green Roof in a midwestern u s climate
Energy and Buildings, 2011Co-Authors: Kristin L Getter, Bradley D Rowe, Jeffrey A Andresen, Indrek S WichmanAbstract:Abstract Green Roofs, or vegetated Roofs, can reduce heat flux magnitude through a building envelope as a result of insulation provided by the growing medium, shading from the plant canopy, and transpirational cooling provided by the plants. This study quantifies the thermal properties of an inverted 325 m2 retro-fitted extensive Green Roof versus a traditional gravel ballasted inverted Roof in a Midwestern U.S. climate characterized by hot, humid summers and cold, snowy winters. In autumn, Green Roof temperatures were consistently 5 °C lower than corresponding gravel Roof temperatures. Even during chilly and moist conditions, the heat flux leaving the building was lower for the Green Roof than the gravel Roof. Temperatures at the top of the insulation layer were more variable for both Green Roof and gravel Roof on winter days with no snow cover than on days with snow cover. Variation in temperatures between Roof types in spring was similar to those in autumn. Peak temperature differences between gravel and Green Roof were larger in summer than other seasons (sometimes by as much as 20 °C). Over the course of a year (September 2005–August 2006), maximum and minimum average monthly temperatures and heat fluxes were consistently more extreme for the gravel Roof than the Green Roof.
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quantifying the effect of slope on extensive Green Roof stormwater retention
Ecological Engineering, 2007Co-Authors: Kristin L Getter, Bradley D Rowe, Jeffrey A AndresenAbstract:Abstract Impervious surfaces, such as Rooftops, parking lots, and roads, increase runoff and the potential for flooding. Green Roof technologies, which entail growing plants on Rooftops, are increasingly being used to alleviate stormwater runoff problems. To quantify the effect that Roof slope has on Green Roof stormwater retention, runoff was analyzed from 12 extensive Green Roof platforms constructed at four slopes (2%, 7%, 15%, and 25%). Rain events were categorized as light ( 10.0 mm) (>0.39 in.). Data demonstrated an average retention value of 80.8%. Mean retention was least at the 25% slope (76.4%) and greatest at the 2% slope (85.6%). In addition, runoff that did occur was delayed and distributed over a long period of time for all slopes. Curve numbers, a common method used by engineers to estimate stormwater runoff for an area, ranged from 84 to 90, and are all lower than a conventional Roof curve number of 98, indicating that these Greened slopes reduced runoff compared to traditional Roofs.
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watering regime and Green Roof substrate design affect sedum plant growth
Hortscience, 2005Co-Authors: Nicholaus D Vanwoert, Bradley D Rowe, Jeffrey A Andresen, Clayton L Rugh, Lan XiaoAbstract:Green Roofs are an increasingly common, environmentally responsible building practice in the United States and abroad. They represent a new and growing market for the horticulture field, but require vegetation tolerant of harsh environmental conditions. Historically, Sedum species have been the most commonly used plants because, with proper species selection, they are tolerant of extreme temperatures, high winds, low fer- tility, and a limited water supply. A Greenhouse study was conducted to determine how water availability influences growth and survival of a mixture of Sedum spp. on a Green Roof drainage system. Results indicate that substrate volumetric moisture content can be reduced to 0 m 3 ·m -3 within 1 day after watering depending on substrate depth and composition. Deeper substrates provided additional growth with sufficient water, but also required additional irrigation because of the higher evapotranspiration rates resulting from the greater biomass. Over the 88 day study, water was required at least once every 14 days to support growth in Green Roof substrates with a 2-cm media depth. However, substrates with a 6-cm media depth could do so with a watering only once every 28 days. Although vegetation was still viable after 88 days of drought, water should be applied at least once every 28 days for typical Green Roof substrates and more frequently for shal- lower substrates to sustain growth. The ability of Sedum to withstand extended drought conditions makes it ideal for shallow Green Roof systems.
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Green Roof stormwater retention effects of Roof surface slope and media depth
Journal of Environmental Quality, 2005Co-Authors: Nicholaus D Vanwoert, Bradley D Rowe, Jeffrey A Andresen, Clayton L Rugh, Thomas R Fernandez, Lan XiaoAbstract:: Urban areas generate considerably more stormwater runoff than natural areas of the same size due to a greater percentage of impervious surfaces that impede water infiltration. Roof surfaces account for a large portion of this impervious cover. Establishing vegetation on Rooftops, known as Green Roofs, is one method of recovering lost Green space that can aid in mitigating stormwater runoff. Two studies were performed using several Roof platforms to quantify the effects of various treatments on stormwater retention. The first study used three different Roof surface treatments to quantify differences in stormwater retention of a standard commercial Roof with gravel ballast, an extensive Green Roof system without vegetation, and a typical extensive Green Roof with vegetation. Overall, mean percent rainfall retention ranged from 48.7% (gravel) to 82.8% (vegetated). The second study tested the influence of Roof slope (2 and 6.5%) and Green Roof media depth (2.5, 4.0, and 6.0 cm) on stormwater retention. For all combined rain events, platforms at 2% slope with a 4-cm media depth had the greatest mean retention, 87%, although the difference from the other treatments was minimal. The combination of reduced slope and deeper media clearly reduced the total quantity of runoff. For both studies, vegetated Green Roof systems not only reduced the amount of stormwater runoff, they also extended its duration over a period of time beyond the actual rain event.
Jeremy T Lundholm - One of the best experts on this subject based on the ideXlab platform.
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Green Roof plant species diversity improves ecosystem multifunctionality
Journal of Applied Ecology, 2015Co-Authors: Jeremy T LundholmAbstract:Summary Constructed ecosystems such as Green Roofs often contain monocultures or low-diversity plant communities, but adding more plant species to these systems can increase ecosystem service provisioning. Mixture advantage, when species-rich treatments outperform the best monocultures, is desirable in constructed ecosystems due to the cost of increasing diversity. However, there have not been any studies in constructed ecosystems that have quantitatively compared mixtures with the best monocultures for multifunctionality, and there have been few studies that have examined how provision of ecosystem services changes over time as plant communities develop. In a Green Roof system, I predicted (i) that the mixture advantage would be stronger for ecosystem multifunctionality than for single ecosystem functions and (ii) that ecosystem service provisioning and complementarity in above-ground biomass would increase over time. Fifteen monocultures of plant species from five life-form groups (succulents, tall forbs, dwarf shrubs, creeping forbs, grasses) were compared with three-species mixtures of the same life-form and mixtures of species from three and five different life-forms in a modular Green Roof system. Indicators of ecosystem services including above-ground production, thermal regulation, stormwater retention, nutrient uptake and carbon sequestration and two indices of ecosystem multifunctionality were compared. Canopy density increased over time while substrate temperature decreased, suggesting higher provisioning of valuable ecosystem services. For single services, the positive relationship between planted species richness and ecosystem service grew stronger over time, but was consistently strong over time for multifunctionality. Quantile regression indicated a weak mixture advantage for several services including both multifunctionality indices. While the effects were small, different species optimized different functions, thus multifunctioning is enhanced in more diverse mixtures by combining species that maximize different functions. Tripartite partitioning of canopy density showed that overyielding and trait-independent complementarity fluctuated between years in response to shifts in species abundances, but dominance and trait-dependent complementarity increased over time. Synthesis and applications. This study provides the first evidence in a constructed ecosystem that mixtures can outperform the best monocultures for multiple ecosystem services. Mixtures of plant life-forms can improve Green Roof performance. The biodiversity–ecosystem function relationships observed in natural ecosystems can also occur in novel and highly simplified engineered ecosystems.
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performance evaluation of native plants suited to extensive Green Roof conditions in a maritime climate
Ecological Engineering, 2011Co-Authors: Scott J Macivor, Jeremy T LundholmAbstract:Abstract Assessing plant species performance on extensive Green Roofs can inform about and improve Green Roof functioning, aesthetics, longevity and the diversity of plant palettes available for the Green Roof industry. In this study, we evaluate survival, cover, Roof cooling and stormwater retention properties of 15 plant species native to coastal regions of Atlantic Canada in extensive Green Roof monocultures. After a complete growing season (May–October 2009), all but one species had greater than 80% survival, and 10 species reached greater than 90% groundcover. Over the growing season, the top performing species reduced Roof surface temperature by an average of 3.44 °C and increased solar reflectivity by 22.2% over the growing-medium only controls. Moreover, the best species retained 75.3% of experimentally added stormwater. Our results demonstrate that several species (mainly graminoids) performed better than creeping shrubs and forbs for most functions, although significant variation existed within life-form groups.
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plant species and functional group combinations affect Green Roof ecosystem functions
PLOS ONE, 2010Co-Authors: Jeremy T Lundholm, Scott J Macivor, Zachary Macdougall, Melissa RanalliAbstract:Background Green Roofs perform ecosystem services such as summer Roof temperature reduction and stormwater capture that directly contribute to lower building energy use and potential economic savings. These services are in turn related to ecosystem functions performed by the vegetation layer such as radiation reflection and transpiration, but little work has examined the role of plant species composition and diversity in improving these functions. Methodology/Principal Findings We used a replicated modular extensive (shallow growing- medium) Green Roof system planted with monocultures or mixtures containing one, three or five life-forms, to quantify two ecosystem services: summer Roof cooling and water capture. We also measured the related ecosystem properties/processes of albedo, evapotranspiration, and the mean and temporal variability of aboveground biomass over four months. Mixtures containing three or five life-form groups, simultaneously optimized several Green Roof ecosystem functions, outperforming monocultures and single life-form groups, but there was much variation in performance depending on which life-forms were present in the three life-form mixtures. Some mixtures outperformed the best monocultures for water capture, evapotranspiration, and an index combining both water capture and temperature reductions. Combinations of tall forbs, grasses and succulents simultaneously optimized a range of ecosystem performance measures, thus the main benefit of including all three groups was not to maximize any single process but to perform a variety of functions well. Conclusions/Significance Ecosystem services from Green Roofs can be improved by planting certain life-form groups in combination, directly contributing to climate change mitigation and adaptation strategies. The strong performance by certain mixtures of life-forms, especially tall forbs, grasses and succulents, warrants further investigation into niche complementarity or facilitation as mechanisms governing biodiversity-ecosystem functioning relationships in Green Roof ecosystems.
Martin Hermy - One of the best experts on this subject based on the ideXlab platform.
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adapting Green Roof irrigation practices for a sustainable future a review
Sustainable Cities and Society, 2015Co-Authors: Carmen Van Mechelen, Thierry Dutoit, Martin HermyAbstract:Abstract Sustainable water management is an important global action to alleviate the growing pressure on our water resources and a way to balance both socio-economic and environmental water needs. Irrigation of Green Roofs and other urban Green infrastructures often has a negative connotation in a water management context. This is especially the case in semi-arid regions where both water scarcity during summer and other water needs compromise the public support of urban irrigation systems. However, irrigating Green Roofs is also beneficial as it improves plant survival and temperature control. Information on Green Roof irrigation is still very scarce, and this review attempts to draw attention to alternative water sources and water conservation strategies in order to make Green Roof irrigation practices more sustainable. Suggestions for more sustainable Green Roof irrigation showed that water can be conserved by adapting irrigation requirements (i.e. by targeting the vegetation or materials), by using alternative irrigation sources (e.g. gray water and rainwater harvesting) or by controlling and monitoring irrigation regimes. Based on the deficit irrigation strategy, irrigation specifications for Green Roofs in different climates were proposed. It became clear that irrigation is essential during establishment and the first growing season on all types of Green Roof and in all climates here considered. Afterwards, irrigation is necessary on Green Roofs in (semi)-arid climates, and advised in small amounts in the other climates. If public awareness of sustainable water consumption is promoted and if Green Roofs are designed carefully, then irrigation practices can be sustainable in the long term and contribute to better urban life quality.
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Plant trait analysis delivers an extensive list of potential Green Roof species for Mediterranean France
Ecological Engineering, 2014Co-Authors: Carmen Van Mechelen, Thierry Dutoit, Jens Kattge, Martin HermyAbstract:Green Roofs are increasingly popular in urban areas of NW Europe and North America. However, Green-ing Roofs still needs incentives particularly in countries with a Mediterranean climate. Although Green Roof benefits such as cooling capacity and storm water retention would be even more pronounced in this challenging climate with hot and dry summers, vegetation stress on extensive Green Roofs will be enhanced, causing low performance if the same species as in the temperate regions of NW Europe and North America are used. In order to support further development and application of Green Roofs in the Mediterranean climate, new insights on suitable native species is an essential step. Using the habitat template concept, specifically taking into account drought adaptation and self-regulation, we developed a screening procedure using both functional plant traits and utilitarian aspects. Plant traits of two species lists (one resulting from an extensive vegetation study and another one covering the successful plant species of extensive Green Roofs in NW Europe) were analyzed. The results were incorporated into a hierarchical multi-criteria screening tool. This tool can encourage further experimental trials and inspire and guide the Green Roof industry toward the most appropriate species for extensive Green Roof design. As an example, the key was illustrated on a subset of plant species from Mediterranean southern France, which identified 34 newly potential Green Roof species. Interestingly, 35% of these species were annuals, a promising life form that has until now rarely been considered for extensive Green Roofs.
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mediterranean open habitat vegetation offers great potential for extensive Green Roof design
Landscape and Urban Planning, 2014Co-Authors: Carmen Van Mechelen, Thierry Dutoit, Martin HermyAbstract:Abstract Offering a wide array of benefits, Green Roofs have become an important tool for improving urban environmental quality mainly in regions with a temperate climate. However, Green Roofs seem to perform relatively bad in the Mediterranean, as plant species commonly used are often not adapted to cope with the additional stress factors associated with this climate. The habitat template hypothesis states that potential species can be found in habitats with similar conditions as on extensive Green Roofs. In this study, natural open habitats in southern France are described and variation in species composition in relation to environmental factors is analyzed. 372 local species recorded in 20 locations were grouped in four major vegetation types. These results are compared with a list of species commonly used on Green Roofs in NW Europe. 79% of the species found in these open habitats are currently not used on Green Roofs. Ten highly relevant plant traits for extensive Green Roofs were then used to screen the species found during the field work. 28 species scored highly in this screening procedure, indicating good potential. Annual species are currently rarely regarded for Green Roof purposes but in the habitat template context, this life form is an important part of Mediterranean vegetation and should be considered in Green Roof design. This research offers the ecological fundamental knowledge necessary for further selection and testing of species and final implementation into a successful Green Roof system.
