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The integration of vertical greening systems and green roofs with buildings is currently a popular urban development approach aimed at mitigating the urban heat island effect and promoting sustainable development. However, most existing studies on vertical greening systems and green roofs are based on short-term experimental results, which might not reflect their overall performance. Thus, this paper aims at evaluating the energy performance of vertical greening systems and green roofs in a hot summer and cold winter region in China over a three-year period. Although energy-saving was found in summer, occasionally increases in energy demand occurred in winter. It confirms the need for long-term experiments to avoid contingency. The energy saving rate of vertical greening systems and green roofs was approximately 27.49 %-42.48 % (monthly) or 28.89 %-34.02 % (quarterly) during the cooling period (33.84 % on average), and approximately −7.42 %-13.79 % (monthly) or −1.19 %-6.58 % (quarterly) during the heating period (3.6 % on average). The impact of climatic conditions on energy saving rate was evaluated. It was found that solar radiation intensity is the most important factor, followed by the outdoor air temperature and relative humidity. This paper provides an insight on the long-term energy-saving benefits of vertical greening systems and green roofs in hot summer and cold winter regions and the correlation between climatic conditions and energy saving rate. • Long-term energy performance of Vertical Greening System was evaluated. • Impact of climatic conditions on energy savings was analyzed. • Averaged energy savings of approximately 33.84 % during cooling period. • Approximately 3.60 % saving during heating period with intermittent negative saving. • Results from short-term energy-saving data might be bias. [ABSTRACT FROM AUTHOR]

Low-maintenance extensive green roofs hold the potential for adapting to climate change, but there is a limited understanding of their effective design in humid subtropical regions. In this study, we aimed to investigate low-maintenance green roof ecosystems capable of thriving under heat stress. Plant growth performance was evaluated in the second year of an experimental green roof in southwest China. This green roof was unirrigated and involved two plant communities (forbs and grasses) cultivated in four substrate types. Metrics of growth performance, including plant survival, green coverage, visual appearance, leaf stomatal conductance, and substrate volumetric water content were used to analyze the impact of substrate on plant growth. ESP substrate, comprising 30 %v (percent of volume) expanded shale, 25 %v perlite, 25 %v vermiculite, and 20 %v compost, featured the highest porosity and optimal growth of forbs, achieving an average green coverage of 66.76 % and average visual appearance value of 3.56 throughout the monitoring period. The high total porosity of this substrate could be critical in facilitating root development and drainage. Moreover, during the summer's heat and drought, while substrate water content is not a limiting factor for the survival of some established forbs, it remains crucial for the growth of grasses. Additionally, the same substrate impacts different plant communities variably. Four particularly well-performing forb species, namely Lycoris chinensis , Tradescantia pallida , Liriope muscari , and Salvia farinacea , demonstrated survival rates closed to 100 % and an average visual appearance value exceeding 3 was noted, and thus, they are recommended as plant candidates for unirrigated green roofs. The distinguished performance of these species is attributable to their adaptation to heat and drought through specific physiological traits. Our findings provide insights into vegetation selection and substrate optimization for the successful establishment of extensive green roofs that could be feasibly developed without irrigation in the humid subtropical regions. [Display omitted] [ABSTRACT FROM AUTHOR]

Green roofs (GR) are nature-based solutions for climate change adaptation and mitigation in buildings and cities. However, few GR maintenance, installation, and challenge-solving guidelines are available for semiarid climates. We present how three case-study types of GR (urban gardens (UGR), native gardens (NGR), and wetland roofs (WR)) varied in installation costs, irrigation volumes, maintenance times, vegetation cover, survival, biomass and yield, in Ensenada, México, from 2022 to 2023. In UGR, nine edible species were cultivated to yield produce; in NGR, six native plants were planted, and four were grown in WR. UGR installation costs were 31 % and 21 % lower, but maintenance costs were four and 1.5 times higher than NGR and WR, respectively. UGR consumed 17 % more water annually than NGR and 42 % less than WR. Likewise, UGR demanded 94 and 92 % more annual maintenance time than NGR and WR. WR presented the highest survival, height, cover, and biomass values, followed by NGR (except for biomass) and UGR. Our results point to different GR solutions for distinct types of applications and users, demonstrating their versatility in design. All GR categories are suitable to reduce the ecological footprint of buildings; however, we emphasize that each GR design involves different economic, time, and challenge-solving commitments that should be considered before installation and operation. • We studied the economic, labor, and irrigation costs of three extensive green roofs. • We provide maintenance guidelines from a Mediterranean climate case study. • Urban Garden roofs demand more maintenance but can be very productive. • Wetlands and Native Gardens have high installation costs and low maintenance. • Green roofs are highly adaptable for distinct types of applications and users. [ABSTRACT FROM AUTHOR]

Green roofs (GRs) are vital for shaping the material cycles of urban ecosystems as a form of distributed green infrastructure. However, current studies have predominantly focused on the material exchange between GRs and the urban environment, neglecting the internal distribution and equilibrium of constituent elements. By monitoring carbon (C), nitrogen (N), and phosphorus (P) in Sedum lineare Thunb and four substrates throughout the seasons, this study analyzes the ecological stoichiometric characteristics of an extensive GR in Nanjing, China. Intra-annual ratios of C:N (46.02, 13.38, 15.40), C:P (252.41, 57.85, 47.22), and N:P (5.75, 4.23, 3.84) were identified in the plant, substrate, and substrate microbial biomass, respectively. The intra-annual ratios of plant to substrate C, N, and P were roughly 9:1, 7:3, and 6:4, respectively. The use of different substrates resulted in significant variations in plant C, N, and P levels and their quantitative ratios, leading to distribution differences of these elements. Furthermore, substrate C, N, and P levels exhibit a generalized threshold effect on microbial biomass and plant C, N, and P concentrations. Notably, the substrate demonstrates an organic C sink potential of 7.11 g/kg/season, surpassing that of plants in unit mass. These findings contribute to understanding the distribution and dynamics of C, N, and P elements within extensive GRs. [ABSTRACT FROM AUTHOR]

Incentive policies to promote new technologies is a strategy often employed by policymakers and governments. In some cities worldwide, mechanisms to encourage the adoption of Green Roofs (GR) have been implemented over the years. Although GR is not a new technology, the use of incentives, such as subsidies and tax abatements and/or exemptions, is still a recent strategy in many countries. The study covered in this paper proposes to explore the potential of combined incentive mechanisms for green roofs, using direct incentives (financial subsidies) and indirect incentives (tax/fee rebates). The granting incentives were verified by the feasibility assessment from both private (saved money) and public perspectives (reduction in municipal revenue) using scenarios of abatement percentages for fees and taxes and combining direct and indirect incentives. In addition, priority intervention areas for the installation of green roofs were defined based on three parameters: (i) the proportion of existing green spaces, (ii) urban heat islands and (iii) the potential of the building stock for green roof retrofit. The results show that granting a combined solution can be an effective option for facilitating the implementation of green roof projects. Moreover, the study serves as a decision support guide for politicians, urban planners, and public managers to formulate incentive proposals and make well-informed decisions regarding the incentive policies for GR. • Incentive policies are needed to promote green roofs (GR) on a large scale. • Tax exemptions or reductions reduce the time needed to make a GR project economically viable. • Urban heterogeneity must be considered when formulating GR incentive policies. • Combining different incentive mechanisms drives GR adoption. [ABSTRACT FROM AUTHOR]

Green roofs are a sustainable strategy for improving the eco-environment in urban areas. However, plants on green roofs are increasingly threatened by extreme heat and drought due to climate change. There is a lack of comprehensive understanding of the physiological water demand of green roof vegetation under extreme heat. Therefore, this exploratory study investigated two commonly used Sedum species for urban green roofs (Sedum spectabile Boreau and Sedum alfredii Hance) under extreme heat, considering two treatments: irrigation and non-irrigation. The results indicated that under extreme heat, if without irrigation, the two Sedum species' mean daily water consumption by transpiration was approximately 4.68 g per Sedum plant. However, under irrigation, the diurnal variation of stomatal conductance of the two Sedum species allowed the stomata to remain open throughout the day, resulting in an over-twentyfold increase in mean daily water consumption through transpiration (120.34 g per Sedum plant) and twofold increase in leaf area index. A random forest model showed that multi-environmental factors explained 67.53 % of the variability in stomatal behavior. Photosynthetically active radiation and soil moisture are the primary environmental factors that directly affect stomatal conductance. The irrigation induces stomatal opening throughout the diurnal cycle, ensuring the continuation of vegetation growth and the maintenance of physiological functions under extreme heat, which then contributes to keeping its eco-environmental functions and providing sustainable services, such as cooling and carbon sequestration. The findings of this study can guide planning and managing green roofs in urban areas that face extreme heat events. [ABSTRACT FROM AUTHOR]

Urban greenhouse and green roof cultivation propose a nature-based solution to current socio-ecological challenges in urban ecosystems, as it offers several socio-ecological solutions and benefits. The interdisciplinary techniques for scientific explorations of cognition and perception towards urban green structures could not get the attention of the researchers across varying scientific disciplines, especially in the developing world. Addressing the personal factors involved in human cognition and its subsequent impact on perceptions will lay the foundation for the studies of the field. The study included questions about socio-demographic characteristics and socio-environmental motivations, as well as a set of images depicting potential future of green structures. The study was accomplished in Tabriz city of Iran with 375 participants. The findings showed that individuals prioritize certain types of rooftop green structures based on their personal characteristics and motivations. Additionally, cognitive differences were observed among individuals based on age, gender, and marital status, leading to perceptual differences towards green structures. Socio-environmental motivations activate perceptual responses within individuals, influencing their preferences for specific types of rooftop greenhouses. Understanding the response of individuals towards green structure types is crucial for effective planning and design. This knowledge can enhance the overall success and satisfaction of rooftop green structures projects, leading to greater wellness and a positive impact on the environment. [ABSTRACT FROM AUTHOR]

Planning clean, livable, and resilient cities is challenging. This becomes even more complex when considering the rapid population growth and urban development. The development of nature-based solutions (NbS) is acknowledged as a viable strategy to address this issue. It has multiple human and environmental health benefits under both normal and extreme climatic scenarios. This study aimed to examine how different conditions and factors are linked to the development of NbS for urban climate change adaptation, with a specific focus on stormwater and flooding management. Through a systematic literature review, this study proposes a taxonomy of NbS to better understand the processes and hierarchies involved in developing NbS. The analysis covered multiple factors related to geographical focus and scale, sector, climatic conditions, adaptation and mitigation measures, ecosystem services, and co-benefits. These factors were linked to ten classified NbS approaches and 29 specific NbS interventions. An analysis of 582 empirical studies showed that Sustainable Urban Drainage Systems (SUDS) are the most dominant approaches of NbS for adaptation, followed by Low-Impact Development (LID), Green Infrastructure (GI), Sponge City (SC), and Blue-Green Infrastructure (BGI). Among the different interventions, green roofs play a significant role in providing multifunctional ecosystem services and adaptation benefits such as stormwater and climate regulation. Policymakers and developers aiming to expand the implementation of NbS can consider the taxonomy proposed in this study to choose the right types of NbS and obtain maximum co-benefits. [Display omitted] • A taxonomy for urban NbS is presented. • The global distribution of different NbS concepts and interventions is mapped. • City, urban, and watershed scales provide a clearer perspective in studying NbS. • Sustainable Urban Drainage Systems are the most dominant approaches for adaptation. • Stormwater management utilizing green roofs offers multiple other co-benefits. [ABSTRACT FROM AUTHOR]

The rapid growth of many Mediterranean cities in the past 50 years has led to a deficit of urban green space where water availability is the main limiting factor. The aim of this experiment was to evaluate the establishment performance of six Mediterranean species for use in extensive green roofs in Mediterranean and semi-arid areas. Asteriscus maritimus , Brachypodium phoenicoides , Crithmum maritimum , Limonium virgatum , Sedum sediforme and Sporobolus pungens plants were grown under well-watered conditions and two levels of water-deficit conditions to assess the effects of water-deficit on their growth capacity, water consumption, photosynthetic capacity, water relations and aesthetic value (relative appearance). After 88 days, the results showed that the water-deficit treatments affected each species differently and revealed differences in the potential ecosystem service benefits that different species could provide. Sedum sediforme appeared to be the best adapted species to water-deficit in terms of relative appearance; however, this species had the lowest capacity to grow (between 7.55 and 4.72 g) and consume water (between 1.58 and 0.82 mm day−1) under both well-watered and water-deficit conditions, limiting its usefulness for storm water management. Brachypodium phoenicoides and Limonium virgatum showed a satisfactory aesthetical performance under water-deficit conditions and had higher water consumption (between 7.66 and 3.48 mm day−1) and biomass accumulation (between 40.11 and 18.98 g) than Sedum sediforme. By contrast, Asteriscus maritimus showed variable relative appearance results than that species. Crithmum maritimum , a succulent species, showed similar biomass accumulation and water consumption to S. sediforme but lower relative appearance than that species. Sporobolus pungens , a C 4 species, showed the highest water use efficiency at the plant level (between 5.79 and 4.81 g L−1). In summary, B. phoenicoides and L. virgatum are suggested as interesting species to complement S. sediforme in Mediterranean and semi-arid green roofs. [ABSTRACT FROM AUTHOR]

• Small green roofs may offer experiential benefits for people in dense urban areas. • The respondents scored high for perceived restorativeness on the study roof. • Also, e.g. joy, beauty, excitement, tempting nature and fresh air were often mentioned. • Practitioners can use the results in planning and design. Growing and densifying cities set challenges for preserving and enhancing sufficient and good quality green urban environment. Rooftops offer vacant room for additional urban greening that may contribute to the well-being of people and the liveability of cities, but this potential lacks empirical support. In spite of the fact that even small green spaces produce, for example restorative experiences, the literature concerning the experiential and recreational benefits of green roofs is still scarce. To identify the experiential potential of a small urban green roof we explored restorative and other experiences of 178 people visiting a sparsely vegetated green roof in the centre of Helsinki, Finland, using a questionnaire. We showed that the studied green roof provided restorative and other positive experiences to the visitors. The level of perceived restorativeness was relatively high. In addition, the results revealed multiple perceived qualities that reflected visual as well as other sensory experiences, beauty, suitability of the place for oneself and the urban context, nature, desire to explore the place and interestedness, positive excitement, and safety. Furthermore, answers to the open questions revealed a wide range of other observations and feelings, such as peace, joy, excitement and hope. Our study indicates that even a small and rather ascetic accessible green roof has potential to offer a moment of respite in the middle of urban everyday hassle, thus implying that these kinds of solutions may allow for a pinch of beneficial green in places where more diverse and lusher solutions are not possible due to, e.g. the load capacity of a roof. [ABSTRACT FROM AUTHOR]

Green space is fundamental to the quality of life of residents, and as such, urban planning or improvement projects often include strategies directly or indirectly related to greening. Although green space is well established to generate positive effects such as cooling, runoff reducing, and ecological corridor, a few studies have examined the comprehensive process of greening in the urban planning context. To fill this gap in the literature, this study seeks to identify a planning model that determines the location and type of greens based on its multiple effects (e.g., cooling and enhancement of connectivity) and calculates the implementation cost using meta-heuristic optimization algorithms. We obtained 30 Pareto-optimal plans by applying our model to the hypothetical landscape at a neighborhood scale. The results showed a synergistic relationship between cooling and enhancement of connectivity, as well as a trade-off relationship between greenery effects and implementation cost. We also defined critical lots for urban greening that are commonly selected in various plans. We expect our model to contribute to the improvement of existing planning processes by repeating the positive feedback loop: from plan modification to quantitative evaluation and selection of better plans. These optimal plans can also be considered as options for "co-design" by related stakeholders. [ABSTRACT FROM AUTHOR]

• Beijing has a rich resources of the potential green roofs (PGRs), accounting for 19.6% of the study area. • More than 10% of the runoff can be reduced by fully implementing of the PGRs in the north central downtown. • 13 of the 20 flooding underpasses would not have happened in the 7.21 Rainstorm, if only 20% of the PGRs had been greened. Although the study of hydrological performance of green roofs is of great significance to urban water security and sustainable development, large-scale roofs greening within a city range has not received sufficient attention. In this study, a typical urban area of 675 km2 within the fifth ring road of Beijing was chosen as a case study. The potential green roofs were defined before being identified from high resolution images. Under three retrofitting scenarios (100%, 50% and 20%) of extensive green roofs, the hydrological behaviour of potential green roofs was investigated at catchment units by employing the Soil Conservation Service Curve Number model. The behaviour was evaluated finally through two aspects of the runoff reduction effect and the flooding mitigation effect. According to this study, a 19.6% of the potential green roofs within the study area indicates a strong potential for the future greening. In the city scale, the average runoff reduction rates decrease from 9.38% to 6.13% with the increasing return period of rainfall events. Catchments in the core of northern city play key roles in reducing runoff, by more than 10% with the 100% implementation scenario. This study also showed that flooding in 13 of the 20 underpasses would have been avoided in the 7.21 Rainstorm if only 20% of the potential green roofs had been implemented. This study demonstrated a potentially positive hydrological behaviour contributed by roof greening in the future Beijing at a city scale, and effective runoff reduction can be achieved if only with a 50% greening of the potential green roofs. However, urban planners should take notice of the predicament that the deposit of high potential green roofs do not match spatially well to the severe flooding sites. [ABSTRACT FROM AUTHOR]

Abstract Green roofs are often used to cool and insulate the buildings below them, but there is a lack of information about optimum design of green roofs to achieve this function in Mediterranean climates. In such climates, the cooling effect of green roofs can also be important on warm days during the winter. In this study, we compared temperatures of non-green roofs, green roofs planted with Sedum sediforme (Jacq.) Pau, and green roofs planted with the same density of Sedum together with annual plants. These plants were chosen because annual plant communities are an important part of semi-arid environments, which are analogous to green roofs. Temperatures were measured below green roof plots and in the substrate. We found that temperatures below green roofs were around 7 °C cooler than below non-green roofs, and that temperatures below Sedum roofs were, in general, 1.5 °C cooler than below annuals + Sedum roofs. The difference in temperatures between green roofs types was seen in summer in the substrate and in winter below the roof. Substrate moisture was higher in Sedum roofs in the summer. Vegetation cover was higher in annuals + Sedum roofs in winter and in Sedum roofs in summer, as Sedum grown alone grew more than Sedum grown with annuals. Overall, Sedum roofs appear to be more effective in providing cooling benefits in this climate, due to higher substrate moisture and vegetation cover in the summer. Thus, to achieve the cooling benefits of an extensive green roof in a Mediterranean climate, it may be prudent to use succulent species alone, without annuals that would compete with Sedum in winter, while not providing a cooling effect in summer. [ABSTRACT FROM AUTHOR]

Green roof (GR) ecosystems function as a result of a series of complex interactions between plants and substrates, which are poorly understood. This ambiguity hinders the scientific application of GRs to tackle urban eco-environmental problems. The goal of this study was to clarify the response of plants to various abiotic and biotic characteristics of GR substrates, including physical properties, nutrients, and microbes. We systematically analyzed the statistical association between 43 indicators of plant and substrate characteristics using four GR substrates and one common plant type (Sedum lineare Thunb) in a subtropical monsoon climate. Height, coverage, root-shoot ratio, total carbon, total nitrogen, total phosphorus, total potassium, root vitality, and malondialdehyde levels were considered sensitive indicators of the plant's response to the substrate. Substrate nutrients and microbial biomass were most closely associated with the plant response, whereas the material properties of the substrate could indirectly affect plant growth by influencing substrate microbes and plant nutrients. Our results suggest that when optimizing GR substrates for plant responses, it is necessary to respect the plants and account for the abiotic and biotic relationships. It may be possible to manage GR performance in a more scientific and effective manner through the control of substrate microorganisms. [ABSTRACT FROM AUTHOR]

The cooling potential of vegetated roofs depends on the stomatal resistance (r s), leaf area index, and other factors. Sailor (2008) and Tabares-Velasco and Srebric (2012) are among the most cited heat and mass transfer vegetative roof models. They include different equations to estimate r s , which show large differences, and significantly overestimate r s under certain conditions. Therefore, their models offer particular opportunities for improvement to reflect the actual vegetation cooling potential. This is necessary to predict the impact of vegetative roofs more accurately on the building energy performance and the urban heat island effect. The r s of both vegetative roof heat and mass transfer models have been developed based on studies with species that are not commonly planted on vegetative roofs. It was found that both models overestimate the r s under certain conditions that could turn into the underestimation of the transpiration rates and the cooling potential. Consequently, this paper aims to develop a novel equation for r s based on field measurements in a semiarid climate. The species tested were Glandularia berterii (C3), Selliera radicans (C3), Phyla reptans (C3), Aptenia cordifolia (CAM), Sedum palmeri (CAM), and Sedum spurium (CAM). A New Linear Model (NLM) was formulated to estimate r s. The regressors of NLM are minimum stomatal resistance (r s , min), incident solar radiation (R sh), leaf area index (LAI), substrate volumetric water content (VWC), and vapor pressure difference (VPD). The results show that r s , min and R sh reflect 64 % of r s ; the species with higher cooling potential were Selliera radicans , Sedum palmeri, and Sedum spurium due to higher LAI and lower/moderate r s , min ; and, the NLM showed a better agreement with the measured r s , correcting points where Sailor (2008) and Tabares-Velasco and Srebric (2012) equations significantly overestimated r s. Finally, it was demonstrated that the developed NLM better represents the stomatal behavior and distinguishes the responses between C3 and CAM species. [Display omitted] • A novel stomatal resistance equation through a new linear model (NLM) is shown. • The NLM is based on field measurements carried out in a greenhouse. • The NLM can be integrated into heat and mass transfer models of vegetative roofs. • The NLM includes the following variables: r s , min , R sh , LAI , VWC , and VPD. [ABSTRACT FROM AUTHOR]

Green roofs are building-integrated greenery systems that provide many ecological and economic benefits to urban environments. Green roofs are an important component of sustainable drainage systems that can potentially improve the quality of urban runoff. Previous research on the environmental impact of leachate from green roofs on receiving waters have generated unfavourable views on the use of these systems. The sink effect of P, N and heavy metals is ambiguous. The benchmarks used to study source-sink effect are particularly disparate, with leachate from green roofs being compared by some authors to leachate from conventional soils and by others to rainwater. Finally, the use or not of fertilizers during the studies varies the result. This dispersion leads to misinterpretations of the results and conclusions, compromising the future use of green roofs. The articles reviewed and detailed has been ordered according to the possible impacts, comparing results and conclusions. The review confirms the source effect for P from 0.03 to 3.86 mg/l and the source effect for N from 0.4 to 8.3 mg/l. A mixed source-sink effect for P and N can be concluded when fertilizers are not applied and using additional materials, with reductions from 17,4 to 8,4 mg/L in P concentrations and reductions from 14% to 87% in N concentrations. Nutrient leaching can be controlled by appropriate mitigation measures, better system design and management. The source-sink effect for heavy metals, is determined with compared with the rainwater and runoff conventional roofs. The proportions of heavy metals from the green roofs runoff mostly depend on the substrate type. The heavy metals most referenced from the green roof runoff are Pb, Cd, Zn, Fe, Cu and Cr. Finally, a clear consensus is observed on the fact that green roofs mitigate the damage caused by acid rain by increasing pH usually around 8.0. [Display omitted] • Source or sink effect of green roofs is still unclear. • Nutrients and metals are main parameters influencing source-sink effect. • Benchmarks for source-sink effect assessment must be rethought. • Regulatory limits from water quality standards must be considered. • Fertilizers are a source of P and N from green roofs. [ABSTRACT FROM AUTHOR]

Green infrastructure alternatives such as green roofs and walls (GRGW) are part of nature-based solutions for managing complex urban environmental, health, and well-being challenges. The burgeoning acceptance of GRGW, particularly in the Global North, is primarily ascribed to the wide recognition of multiple social, economic, and environmental benefits. To promote more GRGW adoption in the Global South, it is essential to understand its driving forces. However, such studies remain limited. This study aims to identify the GRGW adoption drivers in Ghana. Fourteen key benefits of GRGW were identified from a literature review and a questionnaire survey (N = 505) of stakeholders from 14 groups across five strata in the Greater Accra Metropolitan Area of Ghana. The findings reveal that Ghana's top five GRGW adoption drivers are promoting health and well-being, improving air quality and carbon sequestration, contributing recreational and leisure functions, raising property value, and augmenting aesthetics. Stakeholders prioritized socio-cultural and amenity drivers. Stormwater and flood abatement was weakly endorsed as a significant driver despite Accra's history of flooding. The t -test analysis confirmed that 12 out of the 14 drivers were statistically significant, while Kendall's W test showed fair consensus within the 14 diverse stakeholder groups in their rankings of the driving forces. This study improves GRGW research and development in understudied regions. It may act as a catalyst for the GRGW movement in Ghana and other developing economies. • Stakeholders' perceptions are crucial to GRGW adoption. • Examined stakeholders' view of GRGW adoption drivers in Accra, Ghana. • Tangible socio-cultural drivers garnered positive perceptions and ratings. • Unfamiliarity with the benefits of GRGW was evident in stakeholders' views. • City managers can use the results to promote GRGW adoption. [ABSTRACT FROM AUTHOR]

Highlights • Green roofs have the potential to mitigate urban climate based on species-specific ecophysiological and morphological leaf traits. • Plants with high CO 2 assimilation are more apt to mitigate CO 2. • The ozone forming potential is negligible as the species studied are overall low BVOC emitters. • Species with high stomata density and with hairy, waxy and rough leaves have high potentiality to retain particulate. • The evergreen shrubs contribute to the improvement of air quality also during winter. Abstract Urban greening helps to improve environment quality and human health thanks to the ability of plants to absorb greenhouse gases and remove significant amounts of air pollutants. Green roofs, providing vegetated surfaces in dense cities, can help to mitigate the negative effects of urban pollution. The present study aimed to evaluate the potential ability of fifteen green roof species (Lonicera pileata , Satureja repandens , Hypericum moserianum, Erigeron karvinskianus , Solidago praecox , Rudbeckia sullivantii 'Goldsturm' , Filipendula purpurea , Filipendula vulgaris 'Kahome' , Gaura lindheimeri , Campanula persicifolia , Veronica longifolia , Sedum spectabile , Origanum vulgare , Salvia nemorosa , and Achillea millefolium) to mitigate carbon dioxide (CO 2) and urban pollutant concentration analysing the leaf physiological traits (gas exchange) and morphological structures (stomata, trichomes, epicuticular waxes and cuticular ornamentation) involved in pollutant removal. Furthermore, considering the important role of biogenic volatile organic compounds (BVOC) on the photochemical reactivity of the atmosphere, their species-specific emission was also assessed together with the derived ozone forming potential (OFP). Our results suggested that the potential mitigation capacity based on the investigated traits of the shrubs and herbaceous species was species-specific. The very low potential of all the tested species to form ozone indicated their suitability for urban planning programs. [ABSTRACT FROM AUTHOR]

As the impact of green space shrinkage in urban centers becomes obvious, local and regional authorities must adopt environmental planning policies that can help create new green areas to ensure a good quality of life for citizens, along with the rehabilitation of the natural environment. One approach is the promotion of green infrastructure on buildings, including multi-dwelling apartment buildings. In order to effectively promote green infrastructure on buildings, it is essential to comprehend public attitudes toward green infrastructure, so that suitable and effective strategies can be implemented by policy makers. In this study, eight hundred respondents were asked to provide their views on green infrastructure on buildings, on construction that should take place on blocks of apartments in order to accommodate green infrastructure and on the related benefits that may arise from creating green spaces on buildings. A structured questionnaire and stratified sampling were used for the interviews, which were conducted with apartment owners in two regional units of Athens. The results showed that most citizens are willing to proceed with the installation of a green roof, trellis or vertical garden, in order to improve the aesthetics and functionality of the building they live in. Most of the respondents are not familiar with the energy savings that may occur from the installation of a green roof, vertical trellis or garden and wish for a subsidy from the state in order to implement green building solutions. To conclude, the participants in our study are not environmentally aware, since they are not interested in energy conservation but only about the aesthetics of their building; furthermore, they expect to receive financial support from the state in order to make any changes to their home. [ABSTRACT FROM AUTHOR]

Evidence of heat mitigation through green infrastructure has been extensively documented and quantified in the literature; however, the effectiveness of implementing these strategies regarding thermal comfort at the pedestrian level has not received the same attention. Thus, this paper aims to investigate the role of UGI strategies on pedestrian the thermal comfort in different climatic contexts. Seventy-six peer-reviewed studies were included, analysed and synthesised for their (i) methodological approaches, (ii) pedestrian-level heat mitigation effects. It is seen that there is a positive association of UGI with pedestrian thermal comfort in temperate, continental, arid and tropical climates. Concerning to heat mitigation effects, street trees, green spaces and green walls have great cooling potential. However, green roofs have a negligible effect at the pedestrian level. The evolution of the role of the UGI for pedestrian thermal comfort in different climatic zones reveals the need to develop urban projects based on choosing the "right tree in the right place". Furthermore, the challenges of evaluating the heat mitigation performance of the UGI require procedures to compensate for psychological influences on thermal perception and standardized monitoring protocols to increase the reliability of the results and allow comparisons between different studies. [ABSTRACT FROM AUTHOR]

Urbanization is one of the multiple factors leading to global insect declines. As urbanization grows, green roofs represent a nature-based solution that could provide habitat for plants and animals within cities. Several characteristics of green roofs could enhance insect biodiversity. Nevertheless, little is known about the effects of plant origin on insect abundance from a multi-taxa perspective. Thus, our main goal was to evaluate the effects of plant origin, local resources, and urbanization level on green roofs' overall insect abundance, the abundance of different taxonomic orders, and community composition. Using experimental green roofs, we compared insect communities between native and exotic plants across an urbanization gradient, in Córdoba city, central Argentina. On the roofs of 30 houses, we installed two blocks of a modular extensive green roof system, with either native or exotic plant species (6 species each). In March 2019, we used yellow pan traps and pitfall traps (N = 360) to sample insects and measured flower abundance and plant cover at each plant treatment. The urbanization level of each house was estimated by the Normalized Difference Vegetation Index (NDVI), the Normalized Difference Built-up Index (NDBI), and the Land Surface Temperature (LST). A total of 35,257 insects from 12 orders were registered, with Diptera, Hymenoptera, and Hemiptera as the dominant groups. Native plants supported significantly higher total insect abundance on both types of traps, independently from the urbanization level, flower abundance, or plant cover of each roof. The abundance of most of the taxonomic orders was higher in natives as well, but particular effects of the covariables were detected for certain groups. In addition, plant origin was an important factor for insect composition. Our results highlight that green roof design should prioritize native plants to enhance insect conservation while achieving more sustainable cities. [Display omitted] ● Green roofs can provide habitat and food resources for urban insects ● We tested plant origin effects on insect abundance on experimental green roofs ● Native plants supported higher community-level insect abundance than exotics ● Urbanization level and local resources did not influence overall insect abundance ● Green roof design should prioritize native plants to enhance insect conservation [ABSTRACT FROM AUTHOR]

Green roofs are promoted as an effective nature-based urban heat island mitigation strategy. Green roof cooling and energy-saving benefits have been simulated for various climatic zones, but mainly at the building scale. Due to a lack of fact-based information on neighborhood cooling benefits, green roof construction lags and has rarely been incorporated into urban planning actions. This study investigated the thermal benefits and energy savings of green roofs for the central area of the Xianlin Campus of Nanjing University at the neighborhood scale. Three scenarios were simulated for a hot summer day using a validated ENVI-met model: a base case (S0), extensive green roofs (EGRs) (S1), and intensive green roofs (IGRs) (S2). The air temperature cooling benefit from green roofs extended downwards to the pedestrian level. The EGR scenario achieved a maximum 0.29 °C air temperature reduction at the pedestrian level and 0.37 °C at the rooftop level. The IGR scenario achieved a maximum 0.35 °C air temperature reduction at the pedestrian level and 0.45 °C at the rooftop level. EGRs and IGRs reduced energy demands for air-conditioning by 0.39 kWh·m−2·d−1 and 0.56 kWh·m−2·d−1 and CO 2 emissions by 31,997 kg·d−1 and 45,967 kg·d−1, respectively. These results confirm that green roofs yield substantial cooling and carbon mitigation benefits. Our study provides essential data to establish green roofs as mainstream cooling technology in subtropical cities. The results also imply that urban planners and policymakers may need to embrace the implementation of green roofs in long-term planning and building design practices to improve urban thermal environments, reduce building energy demand, and curb carbon emissions. • Neighborhood-scale green roof scenarios were simulated with a validated ENVI-met model. • Green roofs on low/midrise buildings cool street-/roof-level air up to 0.35 °C/ 0.45 °C. • Green roofs reduce energy demand for air-conditioning by up to 0.56 kWh·m-2 per day. • Green roofs reduce carbon emissions by up to 45,967 kg per day. [ABSTRACT FROM AUTHOR]

Incorporation of strategic green infrastructure into urban settings has a potential to mitigate climate change, urban heat island (UHI) effect, flood risk and subsequent increase in quality of human life in general. UHI induces through low surface albedo, building geometry and absence of greenery and it deteriorates the thermal comfort and well-being of city dwellers and occupants. This study examined the implication of urban green infrastructure on enhanced microclimatic condition in tropical urban perspective while evaluating the best suitable strategy by modeling a designated site with ENVI-met microclimatic software (V4). The calibration procedure of ENVI met has been undertaken through a real ground monitoring process and the software modeling was done for selected urban setting. The model was firstly validated by reconciliation of observed in-situ measurements with simulated values. R -squared ( R 2 ) values for three different surface types such as asphalt, cement and grass were 0.91, 0.96, 0.88 for near ground (0m) and 0.78, 0.81, 0.92 for 1.5 m, respectively. The parametric studies verified that ENVI-met model can be effectively utilized to improve urban micro-scale thermal conditions in tropical Sri Lanka. The numerical simulation model of ENVI-met was used to generate micro-climatic data for the selected area of Colombo metropolitan region with six greening design scenarios such as prevailing UHI condition (T1), trees in curbsides (T2), 100% green roofing (T3), 50% green roofing (T4), 50% green walls (T5) and a combination (T6) of above mentioned green strategies (trees in curbsides+ 50% green roofs+ 50% green walls). Temperature reductions obtained from all green strategies were compared with existing UHI (T1) scenario during peak temperature in given time. The temperature reductions accomplished by T2, T3, T4, T5 and T6 green infrastructure options compared to T1 were 1.87 °C, 1.76 °C, 1.79 °C, 1.86 °C and 1.90 °C, respectively. It can be concluded that strategic design of urban greenery can effectively enhance the urban environment and outdoor thermal comfort in tropical Sri Lanka. [ABSTRACT FROM AUTHOR]

In the present work, field measurement and simulation method were employed to investigate the effects of several green roofs variables on regional thermal environment in Chongqing (29°N, 106°E), China. Field experiments were conducted in two typical places. The real influence of green roofs on ambient environment was analyzed and compared with the simulation results. The software ENVI-met was employed to simulate 29 cases with different factors, including green roofs types, vegetation coverage, building height, arrangement position and regional layouts. With the aim to investigate the effect of the green roofs thoroughly, different design factors of green roofs were taken in consideration. From the aspect of cooling effect, it can be found that enclosing layout has the maximum air temperature drop, which is up to 0.5 °C. From the perspective of the uniformity of regional environmental temperature distribution, the regional thermal environment of scattered layout is better than enclosing and array layout as a whole. In addition, with the same vegetation coverage, the effectiveness of air temperature dropping of the whole region differed according to the arrangement position. Centrally arranging the green roofs upwind can effectively reduce the air temperature of the whole region. These findings can be used to improve the regional thermal environment by designing the green roofs reasonably. [ABSTRACT FROM AUTHOR]

Green roofs are a promising tool to return nature to cities and mitigate biodiversity loss brought about by urbanization. Yet, we lack basic information on how green roofs contribute to biodiversity and how their placement in the urban landscape affects different taxa and community composition. We studied the effects of local and landscape variables on beetle communities on green roofs. We expected that both local roof characteristics and urban landscape composition shape communities, but that their relative importance depends on species characteristics. Using pitfall traps, we collected beetles during two consecutive years from 17 green roofs in Basel, Switzerland. We evaluated the contribution of six local and six landscape variables to beetle community structure and to the responses of individual species. Communities on the roofs consisted of mobile and open dry-habitat species, with both local and landscape variables playing a role in structuring these communities. At the individual species level, local roof variables were more important than characteristics of the surrounding urban landscape. The most influential factors affecting the abundances of beetle species were vegetation, described as forb and grass cover (mainly positive), and roof age (mainly negative). Therefore, we suggest that the careful planning of green roofs with diverse vegetation is essential to increase their value as habitat for beetles. In addition, while beetle communities on green roofs can be diverse regardless of their placement in the urban landscape, the lack of wingless species indicates the need to increase the connectivity of green roofs to ground level habitats. [ABSTRACT FROM AUTHOR]

Green roofs are often claimed to provide a range of environmental, economic and social benefits, or ‘ecosystem services’. These reported benefits, suggests that green roofs could play a significant role in sustainable urban development, and consequently green roofs are now widely used as tools in urban planning strategies. Accordingly, it is relevant to assess whether the benefits of green roofs and comparative advantages over conventional roofs rest on a robust evidence base. A considerable number of studies of the ecosystem services delivered by green roofs have appeared over the last few decades, but a rigorous assessment of the overall level of evidence is lacking. Using a systematic review approach, this study seeks to evaluate the documentation relating to three selected green roof ecosystem services: reduction of the urban heat island effect, reduction of urban air pollution, and reduction of building energy consumption. The number of studies quantifying effectiveness with original data was found to vary significantly from service to service: 17 studies reported cooling at street level ranging between 0.03–3 C°, four reported pollution removal at roof level e.g. removal of small particles, PM 10 , ranging between 0.42–9.1 g/m 2 per year, and 41 reported on building energy consumption, of which 20 were comparable and claimed changes in annual consumption ranging between an increase of 7% to a 90% decrease. The large spans in documented effectiveness are ascribed to heterogeneity in context and design parameters of the identified studies. Analysis of the identified studies suggests that some parameters are of key importance for the effectiveness but further research is needed to clarify the complex relation between ecosystem service effectiveness and the parameters influencing it. [ABSTRACT FROM AUTHOR]

In an effort to increase the accessibility and functionality of shallow green roof systems, the ability of warm-season grasses to provide acceptable growth needs to be further investigated. In the current study, which was conducted during 2011 and 2012, three warm-season grasses (hybrid bermudagrass, Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy ‘MiniVerde’; seashore paspalum, Paspalum vaginatum Swartz ‘Platinum TE’ and zoysiagrass, Zoysia japonica Steud. ‘Zenith’) were established in outdoor lysimeters. The lysimeters were equipped with all necessary green roof layers placed below a coarse-textured substrate that comprised pumice, thermally treated attapulgite clay, peat, compost and zeolite. Half of the lysimeters had a substrate depth of 15 cm, while the other half had a substrate depth of 7.5 cm. Irrigation was applied at crop evapotranspiration (ET c ). Measurements included determination of substrate moisture content, green turf cover (GTC) and leaf stomatal resistance. Significant differences were observed in the values of GTC among the three turfgrass species and the two substrate depths. Zoysiagrass exhibited the best adaptation at the lower depths of shallow green roof systems. At 15 cm substrate depth, zoysiagrass managed to sustain green coverage for the two study periods. In addition, it was the only turfgrass species that managed to perform well at the substrate depth of 7.5 cm. Seashore paspalum exhibited limited green cover at both substrate depths, while hybrid bermudagrass could provide acceptable green coverage only at 15 cm substrate depth. [ABSTRACT FROM AUTHOR]

In the last years, green roofs have become increasingly popular to improve urban life and help overcome environmental challenges. This paper presents a methodology to rank existing built areas when planning green roofs installation on existing buildings. First, the methodology identifies neighborhoods with real possibilities of receiving green roofs. A further refinement uses urban indexes to estimate the green needs of each selected area. The proposed model was successfully applied to Lisbon, Portugal. Old city areas are discharged while neighborhoods with lack of green spaces appear as priority zones to initiate green roofs urban policies. The results identify 79% of Lisbon with real possibilities of incorporating green roofs and 52% with high potential for green roofs retrofit. [ABSTRACT FROM AUTHOR]

Green roofs and green walls are gaining popularity as a means of mitigating a range of environmental impacts associated with urbanisation. Although this technology has been widely implemented in some parts of the world, uptake within Australia has been slow. This might be attributed to a range of factors, including a lack of awareness; a scarcity of urban green infrastructure policies; a lack of examples to give urban designers confidence in the technology; and perhaps also a limited number of professionals capable of installing green infrastructure systems. This paper researches the distribution of green wall and green roof projects in urban Australia, and the possible influence of local government policies and guidelines that have been designed to promote the increase of green infrastructure in Australia's cities. Differences were observed among project distributions and frequency, both within and between cities. In addition, councils that offered policy instruments and guidance tended to have more green wall and green roof projects than those which have no such policies in place. Compared to successful examples seen internationally, further policy implementation in Australia could increase the frequency of green infrastructure projects, indicating that governmental influence may play a substantial role in encouraging green infrastructure installation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Green roofs provide many ecosystem services such as regulation of building temperatures, reducing urban heat-island effects and draining rainwater. In addition, they are expected to reduce the high levels of CO 2 concentrations in big cities. Previous CO 2 fixation studies on green roofs were done by taking long-time-period samples using expensive equipment and with limited replication. To plan green roofs for optimal CO 2 reduction, a simple method to quantify CO 2 fixation rate in relation to plant species-composition is required. The method we tested is direct measurement of CO 2 concentrations with a portable air-quality meter, which allows a large number of samples. Here we focus on differences in the photosynthetic effect between plots containing the local Mediterranean succulent, Sedum sediforme and plots containing various annuals. In a factorial design (presence or absence of Sedum crossed with presence or absence of annuals), we tested the effect of sedum and annual treatments on CO 2 concentrations. To compare our results with a commonly used method, and to evaluate the role of the different species, we examined the photosynthetic activity at the single plant level under these treatments by using a portable gas-exchange measuring system. We found that our method can detect the effect of different green roof plots and can be used as a simple and reliable tool for green-roof planers. We found that annuals reduced CO 2 concentrations, but only in the absence of Sedum . Sedum alone had no effect on CO 2 concentrations. This emphasizes the importance of integrating plots with annual plants in Sedum -based green roofs. [ABSTRACT FROM AUTHOR]

Understanding of plant growth and flower performance is crucial for appropriate planting design. This study was aimed to understand characteristics of growth pattern and flower performance in green roof plants and how plant species diversity effect these characteristics. A semi-extensive green roof was installed in 2005 and 54 species plant species were planted in 10 cm and 20 cm of the substrate in Rotherham, UK. Thirty-two quadrats (50 cm × 50 cm) were set up through the combinations of plant species diversity (high and low), planting density (high and low). Percentage of coverage and height of each species were recorded at every month from February to November 2006 in these 32 quadrates. Flowering time of each species was studied every two weeks from February to November 2006. Flowering time was various from plants; some showed a very long flowering time, over five months whereas some finished flowering within two weeks. The growth characteristics of individual plant species over time were categorized into six patterns of coverage and vertical growth pattern. Spread of individual plants was larger in high diversity of plants than those in low diversity of plants. Number of flowering was higher and overall flowering term was longer in the quadrats of higher plant species diversity than those of lower plant diversity. However, these tendencies were affected strongly by the combination of species used. Therefore, it is important to be aware of individual plant growth characteristics such as plant size, growth pattern and flower performance for planting design. [ABSTRACT FROM AUTHOR]

Growing media (substrate) is a fundamental part of a green roof, providing water, nutrients and support to plants. However, little research has reviewed how it affects plant performances in different climatic regions. This study aims to analyse published research on green roof growing medium across world’s climate zones. Findings are structured according to Köppen–Geiger climate classification, aiming to investigate the prevalence of research conducted in different climate zones. Results from full-scale studies and laboratory or greenhouse experiments were reviewed. The later were included as they provide systematic knowledge on the effect of individual factors on system performances although cannot provide climate specific information. Studies discussed effects of major substrate components and depths on plant survival and establishment using standard test procedures. Results showed that most research in the subject were in temperate (group C climate classification), continental (group D) and dry climates (group B), respectively. Considerable number of investigations was conducted in controlled laboratory or greenhouse environments. Based on the results, future green roof research and guidelines should consider climate specifications of the region in designing growing medium, depths and attribute of green roof substrates in order to ensure enhanced plant performance. Especially, for more fragile but less investigated dry climate, considerations should be made to tackle heat fluctuations and drought stress by enhancing water holding capacity and thermal isolation of the substrate. To move forward, sustainable building solutions as a part of future urban forms, climate-adaptive green roof systems should be included into future research, practice and guidelines. [ABSTRACT FROM AUTHOR]

Green roofs provide a number of different urban ecosystem services (UESS), e.g. regulation of microclimate, support of air quality improvement, or stormwater retention. To estimate the spatial variation of green roof UESS across an urban area, a GIS-based mapping and spatial analysis methodology was established and applied to the city of Braunschweig, Germany. Based on the analysis of available geodata, in a first step, a quantity of 14,138 rooftops in the study area (14% of all buildings) was found to be generally suitable for greening. This resulted in a green roof area of 3 km 2 . Based on criteria such as roof slope and minimum roof size, nearly two-thirds of these buildings (8596 buildings, 8.6% of total number of buildings) were categorised ‘appropriate’ for greening and subject to green roof UESS analysis. The spatial distribution of green roof UESS was estimated based on the categories thermal urban climate, air quality, stormwater retention and biodiversity. Due to their potential benefits in the four UESS categories an overall assessment resulted in a number of 867 roofs (0.9% of total number of buildings) categorised as ‘high benefit’ from rooftop greening. Another 3550 buildings (3.5%) and 4179 buildings (4.2%) were defined as ‘moderate benefit’ and ‘low benefit’, respectively. The inner city area of Braunschweig appears as a hot-spot of green roof UESS, i.e. higher percentage of ‘high benefit’ green roofs in comparison to residential areas. The proposed method is a simple but straightforward approach to analyse urban green roof UESS and their spatial distribution across a city but it is sensitive to the quality of the available input geodata. [ABSTRACT FROM AUTHOR]

This paper aims to identify and assess the main decision factors that are relevant for the diffusion of green roof technology in cities of temperate climate in Europe. A mixed design method was applied to identify relevant factors and to structure these along a Strengths, Weaknesses, Opportunities and Threats framework. The factors were subsequently assessed by a sample of green roof experts, using an Analytical Hierarchy Process. The results indicate that prospects for green roofs are in general rather bright, and that dissemination potential is substantial. Green roofs are particularly likely to benefit from climate change and respective counter-strategies, as they are seen as an adaptation and mitigation measure. However, current barriers to adoption need to be carefully considered. Especially the dilemmatic incentive structures, in that building owners bear most of the risks and potential disadvantages, while the public collectively benefits from green roof advantages, could be a major implementation barrier. Without supportive policies, green roofs are thus unlikely to move from niche to regime level in the near future. [ABSTRACT FROM AUTHOR]

Green Infrastructure (GI) practices have shown to be promising in mitigating the air pollution in urban areas of several cities across the world. GI practices such as trees, green roofs and green walls are widely used in United States and Europe to mitigate the air pollution. However, there is yet limited knowledge available in identifying the most suitable GI strategy for an urban area in improving the air quality. Furthermore, it is evident that Australia is still lagging behind in adapting GI to mitigate air pollution, compared with US and Europe. Therefore, this study analyzed the air quality improvement through several GI scenarios consisting of trees, green roofs and green walls considering a case study area in Melbourne, Australia by using the i-Tree Eco software. The results were compared with case studies in different cities across the world. The results showed that the i-Tree Eco software can be successfully applied to an Australian case study area to quantify the air quality improvement benefits of GI. The results were further assessed with several environmental, economic and social indicators to identify the most suitable GI scenarios for the study area. These indicators were quantified using different methods, to assess the effectiveness of different GI scenarios. The results showed that, trees provided the highest air pollution removal capability among the different GI considered for the study area. Combination of different GI such as green roofs and green walls with trees did not provide a significant increment of air quality improvement however, has provided more local benefits such as building energy savings. The results obtained from this study were also beneficial in developing policies related to future GI applications in major cities of Australia for the air quality improvement. [ABSTRACT FROM AUTHOR]

Low impact development (LID) practices (e.g., green roofs, bioretention systems, and porous pavements) offer multiple benefits to urban eco-systems. They reduce the expenses associated with water treatment, grey infrastructure, and energy consumption and thus generate economic benefits. They also benefit the environment by mitigating air pollution and climate change, and they provide social benefits such as enhancing livability, urban green space, and educating and improving the health of the public. Many studies have attempted to calculate the monetary value of these benefits. However, few have considered all three types of benefits (i.e., economic, environmental, and social) or considered all of the different LID practices at a city-scale. This study develops a life cycle quantification framework to determine the monetary values of the three types of benefits and the life cycle net benefit of LID practices for a city. Applying the proposed framework to a case study of Hong Kong, the 30-year economic and environmental benefits are 5.3 billion USD and 1.2 billion USD, respectively. The mean and median social benefits are 35.1 billion USD and 49.6 billion USD, respectively. Subtracting the 30-year LID implementation cost (55.8 billion USD) produces a median positive net benefit of 2.3 billion USD with an annual unit value of 1.05 USD/m 2 yr, and a mean negative net benefit of 12.2 billion USD with an annual unit value of −5.58 USD/m 2 yr. Sensitivity analyses show that the net benefit is sensitive to the willingness to pay (WTP) of Hong Kong people, especially the WTP of the private sector, and the land cost of green roofs. Overall, this study provides a framework for quantifying and evaluating the life cycle cost, benefits, and net benefit of LID practices. The assumptions in the framework can be modified based on local information and applied to many other cities worldwide. [ABSTRACT FROM AUTHOR]

Green roofs are known as one of the environmentally-friendly applications and also as a sustainable approach in developing countries. Although many researchers have proven the environmental benefits of installing green roofs all around the world, they have not been used widely in many countries due to the lack of knowledge about cost-benefit issues. This paper places an emphasis on all the private factors affecting cost-benefit analysis. Installation, operation and maintenance costs are compared with the benefits such as energy saving, the increase in property value, and the acoustic effect in order to determine two indicators namely “net present value” and “pay-back period,” using the Monte Carlo simulation. Two scenarios are considered in the analyses: using the property, and selling the property after construction. Moreover, correlation and regression sensitivity analyses are also conducted. The capital of Malaysia, Kuala Lumpur, is selected for the case study due to the lack of cost-benefit analysis in developing countries. The results show that there is low probability of loss in the installation of both types of green roofs during their lifespans. Moreover, net present value for intensive green roofs is found to be higher than extensive ones, whereas the payback period for installing extensive green roofs is lower than intensive green roofs. It is concluded that the probability of loss for the owner is higher than that of benefit in the scenario of selling the property after construction resulting from the installation of both types of green roofs. [ABSTRACT FROM AUTHOR]

A study was conducted in a controlled environment greenhouse to examine the potential of recycled crushed porcelain and foamed glass for use as a component of green roof substrates. Porcelain and foamed glass substrates were compared to heat-expanded shale which served as the control. Each finished substrate was analyzed per German FLL guidelines to determine granulometric distribution, bulk density, total porosity, water-holding capacity, saturated hydraulic conductivity, pH, soluble salts, organic matter content, and cation exchange capacity. Both substrates met FLL Guidelines except the porcelain substrate contained a greater percentage of larger particles and its maximum water holding capacity was lower than recommended. Two plant species were used in the study, Sedum album (stonecrop) and Ocinum x citriodolum (lemon basil). Data collected included substrate volumetric moisture content (VMC), plant growth, biomass accumulation, and plant stress as measured by chlorophyll fluorescence. Substrate VMC was generally greater in shale than in foamed glass or porcelain. At the end of the study plant growth index was greatest for stonecrop growing in shale, but there was no difference among the substrates for basil. However, plants of both basil and stonecrop accumulated the most total biomass when grown in shale. It is probable that water retention could be improved for both recycled crushed porcelain and foamed glass if more attention was paid to reducing particle size during processing. If so, then they may perform equal to heat expanded shale when incorporated into green roof substrates. In the case of porcelain, its use could divert some waste from landfills and greatly reduce the embodied energy required to construct a green roof. [ABSTRACT FROM AUTHOR]

A wide replication of green envelopes can be a good opportunity to improve urban environment conditions, as demonstrated by several studies. Greening systems increase also building envelope performances; however their economic sustainability has not been fully investigated. This study evaluates the economic sustainability of two combined greening systems installed on an office building: a vertical greening system and a green roof, and it evaluates the advantages of economy of scope. The Cost-Benefit Analysis on two different combinations of vertical greening and green roofs considers personal benefits and costs over their life cycle. The results demonstrate the advantages of economy of scope, due to the additional benefits coming from the combination of two different systems. The results show that the tax incentives and the combination of green systems can make the installation and the maintenance costs economically sustainable during the life span of a greening system; this could lead to a wider diffusion of greening systems with higher environmental and aesthetic performances. [ABSTRACT FROM AUTHOR]

Urban areas face severe challenges in mitigating and adapting to climate change within limited space. One solution is to develop multifunctional rooftop systems, which use underexploited urban rooftop spaces. Two main options have been to add greenery by installing extensive green roofs (EGRs) or to generate renewable energy by installing photovoltaic panels (PVs). Recently, combining the two systems on one rooftop (EGR-PV) to harvest both benefits has gained attention. Not every rooftop is suitable for such installations, which makes it difficult to estimate the scale of space a city can expect from rooftops to add greenery, renewable energy, or both. This study presents a geographical potential model using building parameters, a building stock layer, and LiDAR data to simultaneously identify the potential for installing EGRs, PVs, and EGR-PVs on rooftops, highlighting the competition and synergy between EGRs and PVs at the building level. As an empirical illustration to support future multifunctional urban rooftop space planning, Amsterdam was used as a case study. The results show that 47 % of rooftops are suitable for EGRs, which could expand the current greenery space by 6 %, and 55 % are suitable for PVs which could sufficiently provide electricity to households by 2030. Moreover, competition exists for 3.2 %, whereas synergy exists for 42 % of the existing rooftops. • A Spatial Analysis Model that can identify the geographical potential of rooftop systems is developed. • The model can identify the potential synergy and competition between EGRs and PVs for existing urban rooftop space. • An empirical study on the geographical potential of existing Amsterdam rooftops is carried out. [ABSTRACT FROM AUTHOR]

Green roofs provide many ecosystem services, but little is known about the way they contribute to urban functional connectivity. This paper has the following four objectives: (1) to compare the potential green roofs' role to connectivity in relation to other urban green spaces, (2) to specify the green roofs contribution's type, (3) to explore the influence of building height integration method and finally (4) to assess the impact on connectivity of simulated greening new roofs. Using a landscape graph approach, we modeled ecological networks of three species groups with different dispersion capacities in the Paris region (France). Then, we computed several connectivity metrics to assess the potential contribution of green roofs to functional connectivity. At a large scale (metropole scale), our results show that green roofs can slightly improve the global connectivity largely through the connections rather than the addition of habitat area. More than a stepping stone function, green roofs would have a dispersion flux function at a local scale. Furthermore, when the difficulty of crossing movement is exponential to the height of buildings, green roofs over 20 m high are mostly disconnected from the ecological networks. In addition to the green roof's height, our analysis highlights the very strong role played by buildings' configuration. This study raises promising directions for the integration of building height into the analysis of urban connectivity. Detailed research and long-term biological data from green roofs and green spaces are needed to confirm our results. [Display omitted] [ABSTRACT FROM AUTHOR]

The urban forest provides our communities with a host of benefits through the delivery of ecosystem services. To properly quantify and sustain these benefits, we require a strong baseline understanding of forest structure and diversity. To date, fine-scale work considering urban forest diversity and ecosystem services has often been limited to trees on public land, considering only one or two green space types. However, the governance of urban green spaces means tree species composition is influenced by management decisions at various levels, including by institutions, municipalities, and individual landowners responsible for their care. Using a mixed-method approach combining a traditional field-inventory and community science project, we inventoried urban trees in the residential neighbourhood of Notre-Dame-de-Grȃce, Montreal. We assessed how tree diversity, composition and structure varies across multiple green space types in the public and private domain (parks, institutions, street rights of way and private yards) at multiple scales. We assessed how service-based traits – traits capturing aspects of plant form and functions that urban residents find beneficial – differed across green space types, with implications for the distribution of ecosystem services across the urban landscape. Green space types displayed meaningful differences in tree diversity, structure, and service-based traits. For example, the inclusion of private trees contributed an additional 52 species (>30% of total species) not found in the local public tree inventory. Trees on private land also tended to be smaller than those in the public domain. Beyond patterns of tree richness, size, and abundance we also observed differences in the composition of tree species and service-based traits at site-scales, particularly between street rights-of way and private yards. While species composition varied considerably across street blocks, blocks were very similar to one another in terms of mean service-based traits. Contrastingly, while species composition was similar from yard to yard, yards differed significantly in mean service-based trait values. Our work emphasises that public tree inventories are unlikely to be fully representative of urban forest composition, structure, and benefits, with implications for urban forest management at larger spatial scales. • Private land contributed unique species representing over 30% of total tree richness. • Per unit area, tree richness, density, and size were highest in street rights-of-way. • Only analyzing public trees may overestimate the amount of regulating services. • Community science can contribute valuable data supplementing public inventories. • Engaging urban residents is key to promoting urban forest diversity and resilience. [ABSTRACT FROM AUTHOR]

Changing an urban environment and replacing vegetated surfaces with low albedo materials is one of the reasons for increasing temperatures in an urban environment and consequently also one of the key causes of urban heat island effects. In this study, an experimental investigation at the micro-scale and also a numerical simulation at the macro-scale of a typical urban environment in Adelaide were conducted to estimate the potential for mitigating the UHI effect. The results showed that existing low albedo materials such as asphalt, metal roofs and brick pavements contribute to the heat island potential. Also, urban development and a lack of natural vegetation contribute to increased temperatures in cities. The ability of two types of extensive and intensive green roofs to reduce the surrounding micro-climate temperature were monitored. The results showed that they have significant cooling effects in summer time and could behave as an insulation layer to keep buildings warmer in the winter. Furthermore, different scenarios of adding green roofs to the Adelaide urban environment were investigated using the Envi–MET model. The scenario modelling of adding green roofs in a typical urban area in Adelaide, Australia, supported the hypothesis that this can lead to reductions in energy consumption in the Adelaide urban environment. Also an increased use of other water sensitive urban design technologies such as green walls and street trees together with the adoption of high albedo materials is recommended for achieving the optimum efficiency in terms of reducing urban temperatures and mitigating urban heat island effects. [ABSTRACT FROM AUTHOR]

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 (125 mm 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 80.6 mm 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 (g H 2 O leaf area cm −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. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) have been shown to improve the growth, health, nutrient uptake, flowering and drought tolerance of many terrestrial plant species. Green roofs are generally deficient in nutrients, organic matter and water, and therefore AMF could be extremely beneficial in improving green roof plant performance. Despite this there is a lack of empirical research into artificially introducing AMF into green roof substrates. In this study, a commercial AMF inoculum was applied to Prunella vulgaris green roof plugs grown in small modules on a flat roof in Sheffield, UK. The modules were filled with commercial green roof substrate (80% small particle sized crushed brick, 20% green waste compost) to a depth of 100 mm. AMF inoculum was applied as four treatments: (i) directly with plug, (ii) mixed evenly into surrounding substrate, (iii) split between plug and substrate, (iv) control treatment with no inoculum added. Significantly greater levels of AMF colonisation of P. vulgaris roots was detected in all AMF treatments compared to the control. Low levels of AMF colonisation of P. vulgaris roots were also observed in the control treatment, confirming that low levels of AMF inoculum were present in this commercial substrate. Shoot phosphorous (P) concentration was improved in all AMF treatments, however there was no significant effect of any AMF treatment on P. vulgaris growth rate or biomass production. The highest AMF colonisation of P. vulgaris roots was observed when AMF inoculum was directly added to just the plug. Promisingly, P. vulgaris flowering time at the end of the first growing season was also extended in the plug AMF treatment only. This study has confirmed that commercial AMF inoculum can be used to successfully colonise plants and introduce AMF networks into green roof substrate. Although AMF inoculum was naturally present in the substrate used in this study, levels were extremely low, and unlikely to have any significant effect on plants. This study indicates that care should be taken in the use of AMF inoculum on green roofs, as the growth and health benefits of AMF are not always immediately apparent for green roof plants. In addition much more research is required in order to fully assess the extent of the benefits of AMF on green roof plants and to determine if their use can be financially viable. [ABSTRACT FROM AUTHOR]

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 (CO 2 ) and air pollutants, CO 2 sequestration and air pollutants removal. Two roof greening scenarios, extensive (EGR) and intensive (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 consumption, upstream emission and atmospheric concentration of CO 2 . 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. [ABSTRACT FROM AUTHOR]

Use of rooftops to produce locally grown vegetables is increasing. However, due to weight restrictions, shallow substrate depths, and potential harsh environmental conditions, optimizing production can be a challenge. Standard industry practices for ornamental extensive green roofs planted with succulents or other herbaceous perennials and grasses dictate that organic matter should be less than 20% of the original substrate mix. In rooftop agriculture, however, maximizing growth and yields are usually a primary objective and the amount of organic matter incorporated into these substrates are a major factor in this equation. In this study we quantified the optimal percentage of compost in a green roof substrate for optimizing growth and yields for cucumbers ( Cucumis sativus ) and peppers ( Capsicum annuum ). The study was conducted on raised green roof platforms over a period of 19 weeks and compared six substrates containing increasing amounts of a commercial compost produced from municipal yard waste (0, 20, 40, 60, 80, and 100%) mixed with a heat-expanded shale and sand base. These treatments were also compared to a typical garden plot at ground level. Plant performance evaluations such as plant growth, chlorophyll fluorescence (Fv/Fm) as an indicator of plant stress, and fruit yields were used as an indicator for optimal substrate mixtures. Generally, the addition of 60 or 80% compost resulted in the greatest plant growth and fruit yields, although compost influenced growth and yield of peppers to a greater degree than cucumbers. In addition, the ground garden plots performed poorly which emphasizes the point that growing vegetables on a rooftop can be advantage because substrates can be engineered to maximize plant health, although the same could be done with raised beds in a garden plot. [ABSTRACT FROM AUTHOR]

Increasing urbanization, impervious space, and the impact of climate change are threatening the future of cities. Nature-based solutions, specifically urban green infrastructures, are seen as a sustainable strategy to increase resilience against extreme weather events, including the escalating occurrence of stormwater runoff flooding. Consequently, urban planners and decision-makers have pushed their efforts toward implementing green infrastructure solutions to reduce the impact of stormwater floods. Among others, green roofs help store water and decrease stormwater runoff impacts on a local scale. This research aims to investigate the effect of surface permeability and green roof implementation on reducing stormwater flooding and subsequently provide urban planners with evidence-based geospatial planning recommendations to improve urban resilience in Helsinki. First, we modeled the current impact of stormwater flooding using the Arc-Malstrom model in Helsinki. The model was used to identify districts under high stormwater flood risk. Then, we zoomed in to a focus area and tested a combination of scenarios representing four levels of green roof implementation, two levels of green roof infiltration rates under 40-, 60-, 80-, 100 mm precipitation events on the available rooftops. We utilized open geographic data and geospatial data science principles implemented in the GIS environment to conduct this study. Our results showed that low-level implementation of green roofs with low retention rates reduces the average flood depth by only 1 %. In contrast, the maximum green roof scenario decreased most of the average flood depth (13 %) and reduced the number of vulnerable sites. The proposed methodology can be used for other cities to develop evidence-based plans for green roof implementations. • Investigated the benefits of green roof implementation on stormwater flooding. • The methodology is based on geospatial data analysis and planning principles. • The methodology is applied on a case study from Helsinki. • The results reveal the maximum green roof implementation reduces vulnerabilities. • The methodology develops evidence-based plans for green roof implementations. [ABSTRACT FROM AUTHOR]