Implementation Of Green Roofs Research Articles

Evaluating the impacts of greening scenarios on thermal comfort and energy and water consumptions for adapting Paris city to climate change

Recent climate projections predict an amplification of global warming and more frequent extreme events such as heat waves. Therefore, the adaptation of cities to counterbalance these adverse changes is urgent. Among available adaptation strategies, urban greening is a measure that is frequently encouraged to improve thermal comfort or energy demand, but whose impacts are not well known at the scale of cities. In this study we evaluate the effects of various urban greening scenarios based on urban climate simulations across the Paris area. The modelling relies on the Town Energy Balance model. The scenarios tested consist of an increase in ground-based vegetation or an implementation of green roofs on compatible buildings, or the two combined. Results show that increasing the ground cover has a stronger cooling impact than implementing green roofs on street temperatures, and even more so when the greening rate and the proportion of trees are important. Green roofs are however the most effective way to reduce energy consumption, not only in summer but also on an annual basis. The effects the various greening measures may have over different seasons is finally addressed in order to draw up a comprehensive inventory of the climatic impacts of such strategies.

Towards Providing Solutions to the Air Quality Crisis in the Mexico City Metropolitan Area: Carbon Sequestration by Succulent Species in Green Roofs

INTRODUCTION:In the first months of 2016, the Mexico City Metropolitan Area experienced the worst air pollution crisis in the last decade, prompting drastic short-term solutions by the Mexico City Government and neighboring States. In order to help further the search for long-term sustainable solutions, we felt obliged to immediately release the results of our research regarding the monitoring of carbon sequestration by green roofs. Large-scale naturation, such as the implementation of green roofs, provides a way to partially mitigate the increased carbon dioxide output in urban areas.METHODS:Here, we quantified the carbon sequestration capabilities of two ornamental succulent plant species, Sedum dendroideum and Sedum rubrotinctum, which require low maintenance, and little or no irrigation. To obtain a detailed picture of these plants’ carbon sequestration capabilities, we measured carbon uptake on the Sedum plants by quantifying carbon dioxide exchange and fixation as organic acids, during the day and across the year, on a green roof located in Southern Mexico City.RESULTS:The species displayed their typical CAM photosynthetic metabolism. Moreover, our quantification allowed us to conservatively estimate that a newly planted green roof of Sedum sequesters approximately 180,000,000 ppm of carbon dioxide per year in a green roof of 100 square meters in the short term.DISCUSSION:The patterns of CAM and carbon dioxide sequestration were highly robust to the fluctuations of temperature and precipitation between seasons, and therefore we speculate that carbon sequestration would be comparable in any given year of a newly planted green roof. Older green roof would require regular trimming to mantain their carbon sink properties, but their carbon sequestration capabilities remain to be quantified. Nevertheless, we propose that Sedum green roofs can be part of the long-term solutions to mitigate the air pollution crisis in the Mexico City Metropolitan area, and other “megacities” with marked seasonal drought.

A new cooling technique for stingless bees hive

Stingless bees are a type of insect that are very sensitive to the changes of their surroundings, especially to severe heat wave. A report stated that at temperature as high as 38 °C can cause death of bees especially to the pupae. Therefore, the objective of this research is to evaluate a new method in regulating the temperature in the hive. Greenroof, a type of roof which contains green vegetation and soil, was used as the cooling method in this study. Two units of MUSTAFA-hives were exposed under sunlight, one is without temperature control and another one was fitted greenroof. The temperatures inside each hive was measured at two points and was compared with the hive without temperature control. It was found that, for the hive integrated with greenroof, the average hive temperature was about 3°C and 6°C lower in the honey cassette and brood-cells compartment, respectively. Therefore, it can be concluded that the implementation of greenroof could solve the problem of stingless bee hive overheating, and the greenroof has an impressive cooling performance besides being an economic and simple solution.

Integrating ecology into green roof research

Green roofs can provide environmental benefits that include increased building insulation, mitigating urban heat islands, providing aesthetic value, reducing runoff and storm water flooding in urban environments, improving air quality by sequestering pollutants, cooling photovoltaic panels to improve their function, and providing habitat for fauna and flora. Until very recently, improvements of green-roof environmental services had been achieved largely by horticulturalists, engineers, and architects. In recent years, ecologists have increased their participation, implementing ecological theory for enhancing biodiversity, and selecting specific plant assemblages for other environmental services such as carbon sequestration and for providing cooler roofs. Moreover, ecologists can use green roofs as relatively novel habitats for testing and developing ecological theory. This special issue is devoted to fostering input from ecologists for advancing the environmental and ecosystem services of green roofs. A wide range of ecologists can explore the topic of the ecological aspects of green roof design and implementation including island biogeography theory, niche theory and null models, the role of environmental heterogeneity, invasion ecology, and plant selection. They can contribute ecological methodology and study design for strong inference.

Green roof benefits for reducing flood risk at the catchment scale

Among the European countries, Italy is one of the most susceptible to hydrogeological instability events related to the risk of flooding in intensely populated basins, especially inside the Po Valley. A clear example is the Seveso river basin, whose territories are regularly stressed several times per year by flooding events, which in recent years have increased in frequency and intensity. However, it is now impossible to intervene with structural projects aimed at the lamination of flood events, even in modest return periods because of excessive urbanization and continuous residential and industrial expansion. Using extensive and detailed green roof parameters, this study modelled the hydrologic effect of three hypothetical roof greening scenarios at the catchment scale (conversion of 5, 30, and 100 % impervious to green roofs). The modelling of the green roof performances was performed using the Environmental Protection Agency (EPA) Storm Water Management Model (SWMM) and was calibrated over five years of hourly discharge measurements at the closure section of the basin. Hydrologic modelling demonstrated that widespread green roof implementation significantly reduces peak runoff rates and runoff volumes by up to 30 and 35 %, respectively, in the case of 100 % conversion.

Effect of Catchment-Scale Green Roof Deployment on Stormwater Generation and Reuse in a Tropical City

Low-impact development (LID) comprises a broad spectrum of stormwater management technologies for mitigating the impacts of urbanization on hydrological processes. Among these technologies, green roofs are one of the most adopted solutions, especially in densely populated metropolitan areas, where roofs take up a significant portion of the impervious surfaces and land areas are scarce. While the in situ hydrological performance of green roofs—i.e., reduction of runoff volume and peak discharge—is well addressed in literature, less is known about their impact on stormwater management and reuse activities at a catchment or city scale. This study developed an integrated urban water cycle model (IUWCM) to quantitatively assess the effect of uniform green roof deployment (i.e., 25, 50, and 100% conversion of traditional roofs) over the period 2009–2011 in the Marina Reservoir catchment, a 100-km2, highly urbanized area located in the heart of Singapore. The IUWCM consists of two components: (1) a physically based model for extensive green roofs integrated within a one-dimensional numerical hydrological-hydraulic catchment model linked with (2) an optimization-based model describing the operation of the downstream, stormwater-fed reservoir. The event-based hydrological performance of green roofs varied significantly throughout the simulation period with a median of about 5% and 12% for the catchment scale reduction of runoff volume and peak discharge (100% conversion of traditional roofs). The high variability and lower performance (with respect to temperate climates) are strongly related to the tropical weather and climatic conditions—e.g., antecedent dry weather period and maximum rainfall intensity. Average annual volume reductions were 0.6, 1.2, and 2.4% for the 25, 50, and 100% green roof scenarios, respectively. The reduction of the stormwater generated at the catchment level through green roof implementation had a positive impact on flood protection along Marina Reservoir shores and the energy costs encountered when operating the reservoir. Vice versa, the drinking water supply, which depends on the amount of available stormwater, decreased due to the evapotranspiration losses from green roofs. Better performance in terms of stormwater reuse could only be obtained by increasing the time of concentration of the catchment. This may be achieved through the combination of green roofs with other LID structures.

A Review on the Development and Challenges of Green Roof Systems in Malaysia

Green roof system is considered a relatively new concept in Malaysia even though it has been implemented widely in the developed countries. Generally, green roofs provide many benefits such as enhancing aesthetical quality of the built environment, reduce urban heat island effect, reduce energy consumption, improve stormwater attenuation, and reduce noise pollution. A better understanding on the implementation of green roof system in Malaysia is crucial, as Malaysia’s climate is different if compared with the climate in temperate countries where most of the green roof studies have been conducted. This study has concentrated on the technical aspect of green roof system which focuses on i) types of plants and method of planting; ii) engineering design for green roof system; iii) its hydrological performance on reducing stormwater runoff; and iv) benefits of green roofs with respect to energy. Literature review has been conducted to identify the development and obstacles associated with green roofs systems in Malaysia. The study had identified the challenges and potentials of green roofs development in Malaysia. This study also provided the recommendations on standard design and strategies on the implementation of green roofs in Malaysia in the near future. Keywords—Engineering design, green roof, sustainable development, tropical countries.

Green living roof implementation and influences of the soil layer on its properties

Affected by undeniable climatic change, the temperature of the urban areas rises continually, increasing rapidly the energy problem of cities and amplifying the pollution problems. The thermal stress is increased, thus both the indoor and the outdoor thermal comfort levels are decreased, enhancing the health problems. Green roof implementation in the building envelope is strategy that provides heat island amelioration, thermal comfort for occupants and reduces energy consumption of buildings. Green living roofs are a passive cooling technique, which can stop the incoming solar radiation from reaching the building structure below. In this paper, we assessed the importance of the green roofs in providing environmental and building energy benefits, and brief investigation on the different configuration of the soil layer in the green roof assembly influences to the temperature of the roof surface was presented. Investigation was conducted for first phase of the living roof growth. Four cells were designed in SolidWorks software where the transient thermal study was performed in order to determine differences between the behavior of the conventional roof and three green roof types.

Green Roof Cost-Benefit Analysis: Special Emphasis on Scenic Benefits

This article presents a green roof cost-benefit analysis (CBA). Green roofs are roofs which are partially or completely covered by vegetation. We discuss the benefits and costs of light self-sustaining vegetated roofs. The benefits of the ecosystem services (ES) provided by green roofs can be classified into private and public benefits. We apply the selected valuation methods first in Helsinki, Finland and subsequently explain how results can be transferred to other urban locations. Past research and this study show that private benefits are usually not high enough to justify the expensive investment for a private decision maker. However, when the public benefits are added to the private benefits, social benefits are higher than the costs of green roofs in most cases.Past research quantified most types of the benefits, excluding scenic and biodiversity benefits. Scenic benefits denote the intangible benefits that people derive from the presence of green space, including at least aesthetic and psychological ones. In this article, special emphasis is placed on the valuation of the scenic benefits; these are among the most challenging benefits to valuate in monetary terms. We employ hedonic pricing theory, implemented via spatial regression models, and green roof implementation scenarios in order to estimate the aggregate willingness to pay for a “unit” of green roof. The results show that the scenic benefits can be a significant attribute in cost-benefit calculations. Yet, the amount of benefits strongly depends on the green roof design.

Plant establishment on a green roof under extreme hot and dry conditions: The importance of leaf succulence in plant selection

Plant selection for extensive green roofs has largely been based on cool, temperate climate research. However, as green roof implementation in hotter and drier climates increases, there is a need to evaluate plant performance under these climatic conditions. Succulents have been shown to be successful in hot and dry green roofs, although survival differs between species and the role of leaf succulence in survival has not been fully explored. For non-succulent plants, habitats with conditions similar to green roofs (‘habitat templates’) have been used to select plants, although few studies have discussed the performance of these selections under green roof conditions. Therefore, we evaluated establishment of 32 plant species on an unirrigated extensive (125mm deep) green roof in Melbourne, Australia over a 42 week period (from winter through summer into autumn). Plants were selected on the basis of life-form, succulence, appropriate habitat templates and/or successful use on green roofs internationally. Climatic conditions during the experiment were often extreme, with evaporation regularly exceeding rainfall and a hot and dry summer (mean maximum air temperature 35°C and 80.6mm total rainfall), leading to roof temperatures of 65°C. After 42 weeks, only succulent plants remained alive and only three of the succulent species had 100% survival. Survival was positively related to the degree of leaf succulence (gH2Oleaf areacm−1) making this a useful trait for plant selection for unirrigated green roofs in hot, dry climates. The failure of most species, despite being chosen from appropriate habitats, demonstrates the need to evaluate potential plants on green roofs under extreme climatic conditions. Supplementary irrigation may be essential to sustain non-succulent species during extreme weather in hot and dry climates.

Green roofs: A possible best management practice for enhancing the environmental quality of Ghanaian cities

City expansion typically erodes the natural ability of the locale to perform its ecosystem services. This paper discusses green roofs and their potential benefits for Ghanaian cities in terms of improving environmental quality. Limited analysis shows that daily minimum temperatures of cities like Accra are rising faster than the daily maximum thereby decreasing the comfort index of city dwellers. Electricity consumption is increasing amid challenges in supply while the frequency of flooding after rainstorms is also on the rise. Green roofs have demonstrated reduction of these issues in several parts of the world and could help minimize the magnitudes of these issues in Ghanaian cities if adopted as an urban best management practice. Since this technology is new to Ghana with no local research, this paper also discusses the potential economic gains and associated research opportunities as well as some strategies to consider if the green roof technology is to be pursued. Successful introduction and implementation of green roofs in Ghana will depend on awareness creation, research and development of growing substrate, plant species and other structural components, formulation of guidelines for the industry, government support through legislation and provision of incentives to promote its adoption. We hope this paper will initiate discussion between various stakeholders in sustainable city development in Ghana in this era of climate change and variability. Key words: Green roof, urban, environmental quality, best management practice, ecosystem services.

INVESTIGATING THE ENVIRONMENTAL IMPACTS OF GREEN ROOF INSTALLATION

Green roof installation has been used as a sustainable approach for many years in order to reduce the adverse impacts of environmental issues all around the world. These environmental issues include: global warming, air pollution, flood, carbon footprint and so on. Green roofs are practical as a sustainable approach, especially in developed countries; however, there is an increasing trend of implementing green roofs in developing countries. This paper is reviewing the benefits of green roof installation and how green roof might contribute to reduce the negative environmental issues. The environmental problems that can be solved or reduced by these benefits are discussed separately in this paper. It is concluded that due to the environmental benefits of green roof installation, it leads to many economic benefits. Moreover, green roof implementation is beneficial in both urban areas and rural places.

Tool to address green roof widespread implementation effect in flood characteristics for water management planning

Abstract. In the last decades, new approaches were adopted to manage stormwater as close to its source as possible through technologies and devices that preserve and recreate natural landscape features. Green Roofs (GR) are examples of these devices that are also incentivized by city's stormwater management plans. Several studies show that GR decreases on-site runoff from impervious surfaces, however, the analysis of the effect of widespread implementation of GR in the flood characteristics at the urban basin scale in subtropical areas are little discussed, mainly because of the absence of data. Thereby, this paper shows results related to the monitoring of an extensive modular GR under subtropical weather conditions, the development of a rainfall–runoff model based on the modified Curve Number (CN) and SCS Triangular Unit Hydrograph (TUH) methods and the analysis of large-scale impact of GR by modelling different basins. The model was calibrated against observed data and showed that GR absorbed almost all the smaller storms and reduced runoff even during the most intense rainfall. The overall CN was estimated in 83 (consistent with available literature) with the shape of hydrographs well reproduced. Large-scale modelling (in basins ranging from 0.03 ha to several square kilometers) showed that the widespread use of GRs reduced peak flows (volumes) around 57% (48%) at source and 38% (32%) at the basin scale. Thus, this research validated a tool for the assessment of structural management measures (specifically GR) to address changes in flood characteristics in the city's water management planning. From the application of this model it was concluded that even if the efficiency of GR decreases as the basin scale increase they still provide a good option to cope with urbanization impact.

Establishment and performance of an experimental green roof under extreme climatic conditions

Green roofs alter the surface energy balance and can help in mitigating urban heat islands. However, the cooling of green roofs due to evapotranspiration strongly depends on the climatic conditions, and vegetation type and density. In the Southern Central Plains of the United States, extreme weather events, such as high winds, heat waves and drought conditions pose challenges for successful implementation of green roofs, and likely alter their standard performance. The National Weather Center Experimental Green Roof, an interdisciplinary research site established in 2010 in Norman, OK, aimed to investigate the ecological performance and surface energy balance of green roof systems.Starting in May 2010, 26months of vegetation studies were conducted and the radiation balance, air temperature, relative humidity, and buoyancy fluxes were monitored at two meteorological stations during April–October 2011. The establishment of a vegetative community trended towards prairie plant dominance. High mortality of succulents and low germination of grasses and herbaceous plants contributed to low vegetative coverage. In this condition succulent diversity declined. Bouteloua gracilis and Delosperma cooperi showed typological dominance in harsh climatic conditions, while Sedum species experienced high mortality. The plant community diversified through volunteers such as Euphorbia maculate and Portulaca maculate. Net radiation measured at a green-roof meteorological station was higher than at a control station over the original, light-colored roofing material. These findings indicate that the albedo of the green roof was lower than the albedo of the original roofing material. The low vegetative coverage during the heat and drought conditions in 2011, which resulted in the dark substrate used in the green roof containers being exposed, likely contributed to the low albedo values. Nevertheless, air temperatures and buoyancy fluxes were often lower over the green roof indicating that higher evapotranspiration rates compensated for the higher net radiation at the green roof.

Environmental Benefits of Retrofitting Green Roofs to a City Block

Although they are widely in use and in many cases are mandated in Europe and North America, the installation of green roofs has been relatively limited in Melbourne and Australia as a whole. A case study is presented that investigates the implementation of green roofs across the Melbourne central business district (CBD) in Australia. The study aims to give an immediately possible and best-case scenario for the benefits achievable depending on the proportion of Melbourne’s roof area covered with green roofs. The following environmental benefits (EBs) of the retrofit are assessed for both scenarios for a city block: (EB No. 1) reduction in urban heat island (UHI) effect (EBUHI), (EB No. 2) reduction in runoff volume (EBR), (EB No. 3) improved water quality (EBL), (EB No. 4) reduction in storm water runoff peak flow (EBPF), and (EB No. 5) greenhouse gas (GHG) emission reduction (EBGHG). These benefits are then scaled up, assuming that the retrofit of green roofs is expanded to cover the entire CBD roof area in the same proportions. This demonstrates the range and scale of benefits that could be achieved under widespread implementation, such as temperature reductions, significantly reducing the UHI effect, and estimated reductions of storm water runoff peak flow, which may mitigate or reduce the frequency and severity of flash flooding.

‘There's a meadow outside my workplace’: A phenomenological exploration of aesthetics and green roofs in Chicago and Toronto

Green roofs are an increasingly popular urban greening strategy in North American cities. Most green roofs have been sedum-based, but there has been a recent trend to mimic the native habitat of a region in prairie-style green roofs. While this supports ecological restoration goals, it also conflicts with ambiguous responses by urbanites to the aesthetics of ‘wild’ and ‘messy’ nature in the city. Though green roofs are transforming downtown central business districts, there has been little research on office workers’ perceptions of green roofs, or on how they may influence their health, well-being, and experience of central business districts. Furthermore, while recent research has looked at aesthetic perceptions of green roofs, there is scant qualitative work that explains why urbanites may have these preferences, or cultural and contextual factors influencing these perceptions. While not uncontroversial, green roofs make an excellent lens through which to explore the human relationship to nature in cities due to their lack of existing symbolism, challenge of the nature/city divide, and mimicking of native habitat. This paper explores office workers’ perceptions of green roofs in Toronto and Chicago, two cities known for their leadership in green roof implementation. Using a phenomenological analysis of fifty-five semi-structured interviews, this paper examines (a) office workers’ perceptions of green roofs; (b) how their lived experience influences their perceptions of aesthetics and urban nature, and (c) design implications for a more sustainable city. Results show that while ‘wilder’ prairie-style green roofs are not always well-liked, they are more likely to be associated with fascination, creative thinking, and calm well-being than sedum green roofs. Green roofs were also linked to an ethic of care and restoration, and may provide ‘loose fit’ places for respite and better health for office workers.

The Perception of Malaysian Architects towards the Implementation of Green Roofs: A Review of Practices, Methodologies and Future Research

The implementation of green roofs or vegetated roof as a sustainable tool to mitigate the Urban Heat Island effect is relatively new in Malaysia. Although it has not been tested on an urban scale, many research findings have indicated that green roofs can contribute towards enhancing the environmental and aesthetical quality of the built environment. It was hypothesized that the low application of green roofs in the Malaysian construction industry is due to the lack of awareness, understanding and experience in its benefits especially among building practitioners. As a result, this research was initiated to determine the perception and understanding of Malaysian architects in green roofs implementation issues, as well as to identify their level of acceptance and readiness. This paper reviews practices and different research approaches in understanding the factors that influence architect’s perception towards the implementation of green roofs in the Malaysian construction industry. Architects were chosen as the only respondents due to their intensive involvement in the conceptualisation, planning, design and construction stage of a built environment project. Extensive literature review was conducted to explore past experiences in green roof implementation and to develop the theoretical framework for this research.

Literature Review of the Potential Energy Savings and Retention Water from Green Roofs in Comparison with Conventional Ones

Abstract The objective of this study is the comparison of green roof systems with conventional isolated and non-isolated ones in order to identify the potential energy savings of green roofs and the benefits provided in comparison with the cost of construction to the buildings. The region of interest is the Watergraafsmeer area in the city of Amsterdam. The method evaluates literature reports - mostly from 2003 to 2010 - that present the advantages of green roofs. Examples in real implementation of green roofs in USA, UK and Germany, retention of rainfall and a Life Cycle Assessment from a residential construction in Madrid will be introduced, showing the energy savings from insulation and heating/cooling that can be gained. All the reports have shown a reduction in energy costs and in runoff of water. Hence, costs and retrofitting potential completes the research. The age of buildings and the absence of insulation make green roofs an ideal alternative project for the retrofit of Watergraafsmeer.

Green Roofing in Indiana: Case Studies and Design Notes

Green roof technology and implementation are taking root in North America at an accelerating pace. Growing recognition of the benefits of green roofs and increasing interest in green infrastructure are leading to expansion of green roof technologies that have been in use for decades in Europe and elsewhere. While some regions have adopted the use of green roofs on a large scale, other areas are warming up to the concept more slowly. Large-scale implementation of green roofs has not yet occurred in Indiana, but a number of exemplary projects have been constructed, and there are signs that interest in the technology is increasing in the state. The purpose of this article is to provide an overview of green roof technology, analyze selected green roofs in Indiana, explore trends in the state, and address issues for future development of green roof technology in the region. A variety of green roofs were investigated throughout the state. Discussions were held with individuals involved in each project to obtain technical and logistical details of green roof design, installation, and performance.

Scaling of Economic Benefits from Green Roof Implementation in Washington, DC

Green roof technology is recognized for mitigating stormwater runoff and energy consumption. Methods to overcome the cost gap between green roofs and conventional roofs were recently quantified by incorporating air quality benefits. This study investigates the impact of scaling on these benefits at the city-wide scale using Washington, DC as a test bed because of the proposed targets in the 20-20-20 vision (20 million ft(2) by 2020) articulated by Casey Trees, a nonprofit organization. Building-specific stormwater benefits were analyzed assuming two proposed policy scenarios for stormwater fees ranging from 35 to 50% reduction for green roof implementation. Heat flux calculations were used to estimate building-specific energy savings for commercial buildings. To assess benefits at the city scale, stormwater infrastructure savings were based on operational savings and size reduction due to reduced stormwater volume generation. Scaled energy infrastructure benefits were calculated using two size reductions methods for air conditioners. Avoided carbon dioxide, nitrogen oxide (NO(x)), and sulfur dioxide emissions were based on reductions in electricity and natural gas consumption. Lastly, experimental and fugacity-based estimates were used to quantify the NO(x) uptake by green roofs, which was translated to health benefits using U.S. Environmental Protection Agency models. The results of the net present value (NPV) analysis showed that stormwater infrastructure benefits totaled $1.04 million (M), while fee-based stormwater benefits were $0.22-0.32 M/y. Energy savings were $0.87 M/y, while air conditioner resizing benefits were estimated at $0.02 to $0.04 M/y and avoided emissions benefits (based on current emission trading values) were $0.09 M-0.41 M/y. Over the lifetime of the green roof (40 years), the NPV is about 30-40% less than that of conventional roofs (not including green roof maintenance costs). These considerable benefits, in concert with current and emerging policy frameworks, may facilitate future adoption of this technology.