Green Rooftops Research Articles

Projected performance of green infrastructure strategies for flood mitigation in the Ganges-Brahmaputra-Meghna delta

Background: The Ganges-Brahmaputra-Meghna (GBM) delta – the world’s most populous river delta – faces heightened susceptibility to the rise in flooding disasters due to climate change, impacting millions annually. Current flood management strategies are unsustainable and ineffective, and resilient flood management is needed. A promising alternative is the strategic implementation of green infrastructure (GI) applications, which have proven effective in flood management in other regions. Methods: An analysis of the region’s past and future vulnerability to flooding is conducted. Then, green infrastructure performance metrics from regions with similar climatic conditions are extrapolated for the GBM. Green roofs, permeable pavements, and rain gardens were identified as the most suitable GI types for the GBM. Finally, computer simulations were employed to analyze the performance of different implementations of GI within a model city. Results: The simulations showed that 0% green rooftop coverage, 100% permeable pavement coverage, and 40% rain garden coverage were the most feasible GI layout. This configuration resulted in the most preferable balance between cost effectiveness and reduced runoff. Green rooftops were minimized due to high installation costs relative to their retention capacity, whereas permeable pavements and rain garden coverage were maximized. Conclusions: The studies show GI’s potential for flood mitigation and resilience in the GBM region. GI initiatives align with the region's flood mitigation policies and are thus feasible to implement with aid from government incentives. Furthermore, the computer program developed for this analysis could serve as a valuable tool for assessing GI implementation limits and offering guidance to policymakers.

Technology of Forming Roof Top Flowers: Basic Principles

This scientific article rigorously investigates the formation of rooftop flowers, addressing key factors such as climate characteristics, construction requirements, rules, and drainage considerations. Employing a scientific and theoretical approach, the study delves into the technological aspects, including the filter layer and other relevant techniques. The goals encompass understanding the intricate relationship between rooftop vegetation and environmental factors. The research employs systematic methods to explore the theoretical underpinnings and practical implications of rooftop flower construction. Results highlight the significance of meticulous design, robust roof structures, efficient irrigation, suitable plant selection, and sustainable practices. The concluding remarks underscore the importance of these findings in enhancing both the aesthetic appeal and functionality of green rooftops, providing valuable insights for global researchers and practitioners in related fields. Highlights: Innovative Design: Meticulous design principles play a pivotal role in achieving visually appealing and environmentally beneficial rooftop flower formations. Climate-Responsive Construction: The study emphasizes the significance of constructing rooftop gardens resilient to diverse climatic conditions, ensuring long-term viability and adaptability. Effective Drainage Management: Successful implementation relies on optimized drainage systems, preventing water stagnation and safeguarding both the rooftop structure and the underlying environment. Keywords: Irrigation, Drainage, Rooftop Flowers, Green Roof Technology, Sustainable Urban Design

Public attitudes and preferences for green rooftop technologies in the US: a choice experiment

AbstractGreen rooftops, also known as vegetated roofs, will play a critical role in enhancing the resilience of urban areas in the face of climate change and other contemporary environmental and social challenges. To ensure the optimal design and implementation of these green technologies, it is vital to understand the public’s preferences, values, and attitudes toward the government support for green rooftops. This study employs contingent valuation methods, specifically utilizing a payment card and a choice experiment, to investigate these topics that have received inadequate exploration within the current body of literature. Our findings indicate that 45% of the public is aware of green rooftops, and the most desired features on an extensive green rooftop, ranked by importance, are: flowers, grass, trees, and walking paths. The majority (79%) of the public supports a federally proposed legislation currently under review (the Public School Green Rooftop Program) and has a mean willingness to pay of approximately $176 per household as a one-time payment. Additionally, the results show that individuals place a higher value on green rooftops that incorporate solar energy technology compared to those without. Furthermore, there is a perceived, loss of value when access to a green rooftop is limited, as opposed to having open access.

Flood modelling and proposed Blue-Green Solutions – A case study in Lisbon, Portugal

Abstract. This study assesses the potential benefit of Blue-Green Solutions (BGS), green rooftops, rain gardens, permeable pavements, and bioswales, in Lisbon, Portugal. These proposed mitigation measures are applied using TFM-DYN (Nilsson et al., 2021) to simulate potential fluvial flooding distributions from a 10- and 50-year rain event.Water depth of over 30 centimeters can cause damage to infrastructure. The model results show water depths of over 40 centimeters in some parts of the study area for the 10-year return period, raising the need for action. For the 50-year return period even more areas will be affected. These floods can occur at a relatively rapid pace. Four BGS were implemented for flood mitigation. Areas with green roofs and rain gardens showed a lowering in water depth for both return periods. This study shows that even relatively simple data allows for an estimation of urban flooding and the potential effect of BGS for specific locations can easily be determined.

Effect of different foliar treatment and profitable practice of terrace garden in urban environment, Tirupur, Tamil Nadu

Globally, home gardens have been documented as an important supplemental source contributing to food and nutritional security and livelihoods. Terrace garden is usually established on the rooftop of a building. Besides the decorative benefit, roof plantings may provide food, temperature control, hydrological benefits, architectural enhancement, habitats or corridors for wildlife, recreational opportunities, and in large scale it may even have ecological benefits. Green roof tops with living vegetation provide green spaces, mitigation urban heat island, energy conservation, improving the air quality and increases biodiversity. Terrace gardens give pleasure to city dwellers and provide an opportunity for enhancing creativity as well psychological benefits. In addition, they change the visual appearance of the building, screening from neighbors, and conceal unwanted pipeline and unappealing scenery. One such terrace garden was established in terrace portion of a house located in Tirupur, Tamil Nadu. Three different foliar treatments viz., Control (T1), Panchagavya @ 3% (T2) and 19:19:19 @ 1.5% (T3) were given to observe the growth and yield attributes of the Tomato plants. In which Panchagavya @ 3% (T2) recorded the best results in all aspects. In tomato, maximum plant height of 23.4 cm at 35DAS and 42.5 cm at 45DAS, number of leaves as 143 at 35 DAS and 218 at 45 DAS, number of lateral branches as 8 at 35 DAS and 9 at 45 DAS, stem diameter as 0.76 cm at 35 DAS and 1.2cm at 45 DAS, minimum number of days to first flowering as 42 days, minimum number of days to 50% flowering as 58 days, average fruit weight as 93.8g, total yield per plant as 0.62 kg at first picking, 0.65 kg at second picking and 0.68 kg at third picking and Benefit Cost Ratio (BCR) of 1:1.8 was recorded from Panchagavya @ 3% (T2). Besides tomato other vegetable crops such as Brinjal, Bhendi, Chilli, Radish, Lab lab, Spinach and Tropical Amaranth were also grown and calculated Benefit Cost Ratio (BCR). The fixed and variable cost for terrace garden was recorded to be Rs. 1876 and Rs. 554.3 respectively. The gross return and net return obtained from terrace garden were Rs. 1545.5 and Rs. 991.2 respectively. The Benefit Cost Ratio (BCR) obtained from entire terrace garden during the period of 5 months was 1:1.78. The practice of Terrace Gardening is an emerging and important business venture for the urban middle and upper classes families that assure health and profitable benefits.

Impact of green roof on human comfort level and carbon sequestration: A microclimatic and comparative assessment in Dhaka City, Bangladesh

The study determines the impact of rooftop greening in an urban residential area in the microclimate context in Dhaka City Corporation, where the level of carbon sequestration from a green roof of an existing building and it's ability to reach the human comfort zone is focused. The study showed the nature of temperature variation between the green-roofed and bare-roofed buildings. Ten stations were chosen from the study area, where 20 buildings were studied, taking two neighboring buildings (a green- and a bare-roofed) from each station. Air temperature, relative humidity, and air velocity were collected from all floors and rooftops of the selected buildings. The Discomfort Index and Robaa Index have been measured to detect the human comfort zone. Annual carbon sequestration by the plants of the green rooftops was assessed. Findings revealed a significant difference (1o ~ 3.5 °C) of the air temperature between the adjacent bare-roofed and green-roofed buildings. The thermal difference was significant during diurnal hours. The Discomfort Index and Robaa Index were lower in the green-roofed buildings than those of bare-roofed buildings. The annual carbon sequestration in the green roofs ranged from 20.6 tC/ha to 125.4 tC/ha, whereas the equivalent CO2 ranged from 84 to 460 t/ha.

Tendencies of the Green Construction in Russia

With the development of scientific and technological progress and the dense development of large metropolitan areas, the issue of ecology is particularly relevant. The purpose of the study is the study of new technologies that allow existing a green roof. Research methods include analysis, comparison and detailed study of the components of a green roof. We examined in detail the components of the green building on green rooftops in different countries and analyzed the main elements of the green building coverings system. In this article, using concrete examples, the solution of a whole complex of highlighted problems, with the intensive development of green innovations is shown. The result of the research is an evaluation of the effectiveness of the different tendencies of green construction, including the use of green coverings.

Feeding peoples in future: Urban farming and vertical farming

Considering worldwide patterns, for example, environmental changes and asset shortage, a significant test of future urban communities will be to diminish urban impressions. Also, urban communities need to get or stay reasonable for their occupants and offer social and financial chances. Numerous urban areas on the planet are attempting to upgrade manageability by improving urban greenery and advancing urban farming. By introducing green rooftops with urban cultivating, it is conceivable to accomplish natural, social and monetary manageability for the structures in urban communities since it can add to the increasing of natural issues, improvement of network capacities and advancement of urban food security frameworks. Accordingly, reconnecting food production and urban communities offers promising potential. The dissemination of urban cultivating mirrors a rising consciousness of how nourishment and growing can shape our urban areas. A developing number of urban cultivating ventures exist in and on urban structures, including open housetop ranches, housetop nurseries and indoor cultivating as well as vertical gardens can be used to produce foods in densely populated areas where land is insufficient for traditional food production. As vertical space is utilized huge quantity of food is produced which can be supplied fresh in the urban markets.

Green Infrastructure and the Hidden Politics of Urban Stormwater Governance in a Postindustrial City

Infrastructure tells a material story of ongoing challenges in cities, reflecting the diverse, normative desires of different communities. In this article we examine the introduction of green infrastructure technologies into urban infrastructure systems to think critically about these challenges and desires. Green infrastructure is an intentionally designed, multifunctional technology that directly uses or mimics the ecological processes of soils and plants (e.g., green rooftops, rain gardens, and bioswales). Facing budget shortfalls as well as demands to mitigate hazards and green the city, urban leaders are looking at green infrastructure as a facility that can provide diverse cobenefits along with traditional services. A focus on stormwater-based metrics, however—effectively reframing green infrastructure as green stormwater infrastructure—discursively tamps down alternative politics and desires for the city. Through a case study of Pittsburgh’s stormwater governance, we argue that the work to (re)technologize green infrastructure as green stormwater infrastructure is an act of depoliticization that hinders needed conversations about just infrastructure outcomes. We draw on themes from qualitative interviews with community members engaged in urban water governance to suggest that these moments of transition provide an opportunity to illuminate previously obscured infrastructure politics and challenge the forms of knowledge that bind us to conventional routines of urban environmental governance. We see an opportunity to reframe the conversation in a way that opens up opportunities for historically disenfranchised communities to voice their needs beyond the technocratic problem of stormwater management.

Plant survival and growth on extensive green roofs: A distributed experiment in three climate regions

Green rooftops are installed in many climates worldwide to support urban ecosystem services. Across North America, green roofs often make use of the same limited set of plant species, but the effects of regional climates on the survival and growth of a core set of plant species has seldom been investigated. To identify the impact of climate on green roof plant performance, we installed an identical green roof system in three Canadian cities that experience different climate conditions: Calgary, Alberta; London, Ontario; and Halifax, Nova Scotia. The green roofs were monitored across three growing seasons for plant survival, plant height, and canopy density of three species grown in monoculture: Aquilegia canadensis, Sporobolus heterolepis, and Sedum spurium, and a mixture planting with all three species. Green roof vegetation canopy density, plant height and growth rates differed by city, plant species, substrate depth and planting type (monoculture or mixture treatment). Between sites, plant species exhibited different growth phenologies. Mixture treatments performed slightly better than monoculture plantings at each site in canopy density measures but were not significantly greater in plant height measures. The growth rate between years two and three was greatest for the mixture treatment, indicating greater potential for long term survival and performance of mixture plantings. The London, Ontario site, with a relatively moderate climate, supported the best green roof growth and performance compared to the cooler and drier Calgary and the rainier Halifax.

Multi-objective optimization integrated with life cycle assessment for rainwater harvesting systems

The major limitation of optimization models applied previously for rainwater harvesting (RWH) systems is the systematic evaluation of environmental and human health impacts across all the lifecycle stages. This study integrated life cycle assessment (LCA) into a multi-objective optimization model to optimize the construction areas of green rooftops, porous pavements and green lands in Beijing of China, considering the trade-offs among 24 h-interval RWH volume (QR), stormwater runoff volume control ratio (R), economic cost (EC), and environmental impacts (EI). Eleven life cycle impact indicators were assessed with a functional unit of 10,000 m2 of RWH construction areas. The LCA results showed that green lands performed the smallest lifecycle impacts of all assessment indicators, in contrast, porous pavements showed the largest impact values except Abiotic Depletion Potential (ADP) elements. Based on the standardization results, ADP fossil was chosen as the representative indicator for the calculation of EI objective in multi-objective optimization model due to its largest value in all RWH systems lifecycle. The optimization results for QR, R, EC and EI were 238.80 million m3, 78.5%, 66.68 billion RMB Yuan, and 1.05E + 16 MJ, respectively. After the construction of optimal RWH system, 14.7% of annual domestic water consumption and 78.5% of maximum daily rainfall would be supplied and controlled in Beijing, respectively, which would make a great contribution to reduce the stress of water scarcity and water logging problems. Green lands have been the first choice for RWH in Beijing according to the capacity of rainwater harvesting and less environmental and human impacts. Porous pavements played a good role in water logging alleviation (R for 67.5%), however, did not show a large construction result in this study due to the huge ADP fossil across the lifecycle. Sensitivity analysis revealed the daily maximum precipitation to be key factor for the robustness of the results for three RWH systems construction in this study.

Remarkable 3-in-1 Pakis-Stem Green Roofs for Saving Thermal Flat Rooftop

The green councils in the world are often promoting green buildings in terms of energy savings by mitigating the thermal load on buildings,especially thermal rooftop, into the room. Green roofs can be the most effective to lower roof thermal in tropical regions, but complicated and costly to build a perfect green roof even for a simple extensive green rooftop. This research looks for a remarkable growing medium for constructing green roof. Pakis-stem blocks can perform a 3-in-1 function: as a light-weight growing medium for green rooftops, an easy-to-form urban farming in private buildings or residences, and an eco-friendly external roof insulation. After a deep measurement on the rooftop surface and room thermal behaviour, the pakis-stem green rooftop can reduce 16.4oC of surface dry-bulk temperature and approximately 7oC ambient room dry-bulk temperature lower compared to conventional rooftops at noon. Furthermore, the surface temperature and ambient room air temperature difference between Pakis vegetative green rooftops and miana scrub green rooftop is approximately 7oC and 3oC respectively.

Seeking urbanization security and sustainability: Multi-objective optimization of rainwater harvesting systems in China

Urban rainwater management need to achieve an optimal compromise among water resource augmentation, water loggings alleviation, economic investment and pollutants reduction. Rainwater harvesting (RWH) systems, such as green rooftops, porous pavements, and green lands, have been successfully implemented as viable approaches to alleviate water-logging disasters and water scarcity problems caused by rapid urbanization. However, there is limited guidance to determine the construction areas of RWH systems, especially for stormwater runoff control due to increasing extreme precipitation. This study firstly developed a multi-objective model to optimize the construction areas of green rooftops, porous pavements and green lands, considering the trade-offs among 24h-interval RWH volume, stormwater runoff volume control ratio (R), economic cost, and rainfall runoff pollutant reduction. Pareto fronts of RWH system areas for 31 provinces of China were obtained through nondominated sorting genetic algorithm. On the national level, the control strategies for the construction rate (the ratio between the area of single RWH system and the total areas of RWH systems) of green rooftops (ηGR), porous pavements (ηPP) and green lands (ηGL) were 12%, 26% and 62%, and the corresponding RWH volume and total suspended solids reduction was 14.84billionm3 and 228.19kilotons, respectively. Optimal ηGR, ηPP and ηGL in different regions varied from 1 to 33%, 6 to 54%, and 30 to 89%, respectively. Particularly, green lands were the most important RWH system in 25 provinces with ηGL more than 50%, ηGR mainly less than 15%, and ηPP mainly between 10 and 30%. Results also indicated whether considering the objective MaxR made a non-significant difference for RWH system areas whereas exerted a great influence on the result of stormwater runoff control. Maximum daily rainfall under control increased, exceeding 200% after the construction of the optimal RWH system compared with that before construction. Optimal RWH system areas presented a general picture for urban development policy makers in China.

Thermal mitigation of hydroponic green roof based on heat balance

The creation of green rooftops is an important method for mitigating heat build-up in urban rooftop environments because they lower the sensible heat flux over the rooftop and conductive heat flux into the building. We propose a model for assessing thermal mitigation effects through a hydroponic urban greening system based on heat balance. We conducted an experiment with two different rooftops at two study sites, which were monitored for two months in two different years. Each rooftop was divided into two areas: one bare, the other covered by the hydroponic urban greening system. Parameters measured in both areas were air temperature, surface temperature, and conductive heat flux. The data were analyzed using three thermal mitigation indices. However, it was difficult to show a uniform relationship between the latent heat flux and mitigation indices during the period of analysis. This suggests it would be necessary to include factors such as latent heat flux, conductive heat flux, and water heat storage flux to assess the thermal mitigation effect. Our research indicated that the composition of heat balance terms could estimate thermal mitigation effects in the green roof area independent of the year. The results suggest a principle for assessing the mitigation effects of urban greening on the thermal environment.

Bats in the Bronx.

The article discusses the bat population in New York City, New York green roofs through referencing a study co-authored by Kaitlyn Parkins in the journal "Urban Nationalist," including in regard to the bugs as bat food on green rooftops.

Application of sodium polyacrylate and plant growth-promoting bacterium, Micrococcaceae HW-2, on the growth of plants cultivated in the rooftop

This study aimed to evaluate the plant growth-promoting potentials of sodium polyacrylate, a superabsorbent polymer, and Micrococcaceae HW-2, a plant-growth-promoting bacteria. A polymer capable of retaining and continuously supplying moisture was selected and PGPR were isolated from the soil and applied to plants growing in dry environments, such as green rooftops. The moisture absorption and retention abilities of polymer were evaluated at 30 °C and on a rooftop, respectively; the polymer showed water retention potential of 11,110 times after 480 h and 100 times after 74 h. Strain HW-2 produced 128.95 mg/L indole-3-acetic acid on day 5 of incubation, and ACC deaminase activity was found to be 0.322% after 72 h. Synthesis of siderophores was detected by the formation of an orange halo around the colonies on CAS medium. Application of the mixture of HW-2 and sodium polyacrylate to Arundo donax, a drought-resistant plant, significantly enhanced shoot growth and biomass.

Investigation of the Thermal Performance of Green Roof on a Mild Warm Climate

Global warming has become a threat of our time. It poses challenges to the existence of all biota on this earth and has made a clear impact on the level of energy and water consumption. No doubt, increase in the ambient temperature increases indoor and outdoor temperature level of the buildings which catalyzes the use of energy and cost intensive mechanical air-conditioning systems. Green roof tops belong to such an idea for cutting down the energy consumption and enhancing the comfort level of commercial and residential buildings. This paper investigated the impact of green roof on thermal performance and cooling potential in Indian climate. It was observed experimentally that compared to the exposed roof, the room air and interior surface temperature of the green roof were reduced by a maximum of 17% and 22% respectively. Heat flux studies show that not only the peaks are lower but also the diurnal heat fluctuation through the green roof assembly is lower than that of the conventional roof in the case of heat in-leak. Further, a thermal lag of around 2 to 3 hours has been observed. The simulated model developed in this study has been closely replicated by the experimental data, thereby efficacy of the model is demonstrated unequivocally.

Rooftop Surface Temperature Analysis in an Urban Residential Environment

The urban heat island (UHI) phenomenon is a significant worldwide problem caused by rapid population growth and associated urbanization. The UHI effect exacerbates heat waves during the summer, increases energy and water consumption, and causes the high risk of heat-related morbidity and mortality. UHI mitigation efforts have increasingly relied on wisely designing the urban residential environment such as using high albedo rooftops, green rooftops, and planting trees and shrubs to provide canopy coverage and shading. Thus, strategically designed residential rooftops and their surrounding landscaping have the potential to translate into significant energy, long-term cost savings, and health benefits. Rooftop albedo, material, color, area, slope, height, aspect and nearby landscaping are factors that potentially contribute. To extract, derive, and analyze these rooftop parameters and outdoor landscaping information, high resolution optical satellite imagery, LIDAR (light detection and ranging) point clouds and thermal imagery are necessary. Using data from the City of Tempe AZ (a 2010 population of 160,000 people), we extracted residential rooftop footprints and rooftop configuration parameters from airborne LIDAR point clouds and QuickBird satellite imagery (2.4 m spatial resolution imagery). Those parameters were analyzed against surface temperature data from the MODIS/ASTER airborne simulator (MASTER). MASTER images provided fine resolution (7 m) surface temperature data for residential areas during daytime and night time. Utilizing these data, ordinary least squares (OLS) regression was used to evaluate the relationships between residential building rooftops and their surface temperature in urban environment. The results showed that daytime rooftop temperature was closely related to rooftop spectral attributes, aspect, slope, and surrounding trees. Night time temperature was only influenced by rooftop spectral attributes and slope.

Eco-Friendly Buildings: the central factor in transitioning to a Green Economy

The building sector is the largest contributor to global greenhouse gas emissions. More than 33% of global energy use is consumed in offices, homes, and other buildings. This figure is expected to double to more than 60% by 2030. It is a vital requirement, therefore, that new construction projects and renovations to existing construction, are focused on eco-friendly building designs. Such consideration is a low-cost means to battling climate change, reducing energy bills, and diminishing our reliance on fossil fuels. However, a failure to act immediately will compound and multiply the costs associated with climate change. This paper will present building designs and techniques, the goal of which will be to achieve energy neutrality. That is to say that the building’s energy demand will be offset by power generated from renewable energy sources. For instance, in a country such as the UAE, there are high numbers of sunshine hours and a considerable amount of wind potential. It would therefore be best to incorporate solar panels into new building designs. Micro wind turbines, distributed in an aesthetically pleasing way, could supplement the solar panels. Many factors need to be considered when creating an energy efficient building in such a sunny climate. These include: making the best technical use of local resources to avoid the costly (financially and ecologically) long-distance transportation of construction materials; determining the most optimum balance between harnessing the natural sunlight and insulating the inside of the structure from its accompanying heat; and creating natural ventilation and air filtering through design rather than focusing on energy draining air conditioning systems. Of these three, the last may be the most important, as the highest percentage of household energy consumption is associated with cooling/heating living spaces and with heating water. These are two aspects that greatly affect quality of life and that people will not forsake. Their ecological adaptation is therefore necessary in order for populations to adopt more sustainable lifestyles. The focus of this paper will then be about balance: balancing the planet’s and our communities’ future needs with sustainment of home comforts and quality of life. Balance of future urban development with the ecological integrity of our land and water. Balance of ecological building design with natural resource capitalisation. A balance between people and nature. This paper will explore how these goals can be realised through concepts such as incorporation of renewable energies into design; green rooftops; holistic and life cycle approaches to consumption, waste, and recycling; reduced traffic through intelligent pedestrian community design; means of renewable energy transportation; and the reduction of urban heat island effect.

Wetlands are an effective green roof system

Green roofs recently have garnered much attention as a means to reduce both the absorption of solar energy in summer and heat loss in winter, especially in urban areas with limited space for gardening. Constructed wetland roofs maintain more stable temperature profiles than terrestrial systems because of their slow heat transfer and high heat storage capacity. We found that wetland roofs were particularly efficient at decreasing the temperature of green roof systems on hot days. Wetland plants have high evaporation rates that are associated with their ability to cool buildings. Constructed wetland had excellent water holding ability, requiring less than 400 l water/m2 of irrigation over the entire growing season, which was less than 20% of the expected irrigation requirement for terrestrial systems on green rooftops. Wetland macrophyte species demonstrated high tolerance to flooding and drought and showed great potential for regeneration by rhizomes, suggesting easy maintenance. Plants grown in the constructed wetland accumulated high biomass that can serve as a carbon sink. Wetlands on rooftops would not exceed the weight-bearing capacity of rooftops if water depths are designed and kept under 30 cm. Constructed-wetland roofs offer thermal benefits, a low amount of required irrigation, high tolerance of drought and flood, and flood-control capacities. They also can act as a carbon sink, are easy to manage, and provide other ecological services. Therefore, constructed wetlands are a reasonable choice for green rooftop systems.