Green roof systems: a study of public attitudes and preferences in southern Spain

Awareness and willingness to pay for green roofs in Mediterranean areas

Green roofs have been extensively investigated in recent years, showing that their implementation in urban areas provides multiple benefits (e.g., pluvial flood mitigation, urban heat island reduction, energy saving, increase of biodiversity, CO2 sequestration) and supports sustainable urban development. Although green roof benefits have been widely recognized, the perception that the community has of these nature-based solutions and the willingness to pay for their installation in urban areas is still not clear nor quantified. Societal perception and willingness to pay for green roofs are fundamental for urban planners and decision makers, since they represent the community participation in the sustainable development of urban areas. In this work, we aim to analyze how citizens perceive green roofs and how willing they are to pay for the installation and maintenance of these nature-based solutions. We used an online survey to investigate the perception and the knowledge of green roofs as a potential solution to common environmental issues (i.e., urban flood, increase of temperature, energy consumption, air pollution and lack of green spaces), and the interest and willingness to pay for green roof installation on both public and private roofs. Based on the answers of 389 respondents living in Sardinia (Italy), our analysis revealed that most citizens are aware of what green roofs are, and they are aware that, although these nature-based solutions can not completely solve environmental issues, they can greatly contribute to the mitigation of these phenomena. Results also show a higher interest in the installation of green roofs on public buildings than on private ones, due to the high installation costs. Moreover, for private roofs, the possibility to install photovoltaic panels instead of GRs is generally preferred. Most of the respondents are willing to spend less than 100 € per year for the maintenance of green roofs on public buildings and to invest less than 5000 € for the installation on their own house.

Establishment and development of ornamental grasses on green roofs and living walls

Ornamental grasses are often used in gardens to improve biodiversity and as additional aesthetical resources. However, their use in green roofs (GR) and living walls (LW) is not so widespread and it has not been studied extensively. The aim of this work is to assess the performance of seven grass species (Imperata cylindrica ‘Red Baron’, Acorus gramineus, Stipa tenuissima ‘Pony Fails’, Carex flagellifera ‘Bronzita’, Carex oshimensis ‘Evergold’, Uncinia rubra ‘Everflame’ and Miscanthus sinensis) for their use in GR and LW. The growth of the plants was evaluated (i.e. biomass production, dimensions), as well as their visual quality and survival. C. flagellifera and C. oshimensis showed coverage levels greater than 75% and good visual quality, while A. gramineus reached 55–60%. I. cylindrica and M. sinensis showed coverages slightly below 50% in the LW, however, both performed well in the GR, though with a lower visual quality. U. rubra did not develop well, reaching the lowest coverage (below 45%) but maintaining a high visual quality. S. tenuissima also attained low coverage in the LW and presented high mortality, especially in the GR. In LW, C. oshimensis stood out in flowering, while S. tenuissima showed the highest flowering rate in GR. The species should be selected considering their characteristics and performance in order to achieve a correct appearance and development. Interspecific interactions are especially important in LW, as species with upward growth should be placed above species with fallen leaves, not below.

Public Perceptions of Green Roofs and Green Walls in Tokyo, Japan: A Call to Heighten Awareness

Many cities advocate retrofitting green roofs and green walls (GRGW) to create additional green areas, especially in cramped urban areas. Yet, worldwide, only a handful of studies have evaluated the public views towards the benefits and negative issues and promotion policies of this innovative greening option. To address this gap in the literature, we conducted a survey (N = 500) of residents' opinions towards GRGW in Tokyo, a city with mandatory installation of GRGW for almost two decades. Respondents mostly agreed with the contribution of GRGW to thermal comfort, air quality, and cityscape but weakly endorsed other potential benefits. High costs as well as mosquitoes and plant litter nuisances were the most recognized negative issues. Mandatory installation was the least preferred promotion policy. Instead, respondents expected installation on public buildings and provision of installation guidance. Respondents predominantly held a "moderate" view towards both the benefits and negative issues, showing indifferent attitudes towards GRGW. Income level and housing type shaped the overall perceptions, whereas age, sex, and current living environment influenced perceptions of individual aspects. Our findings signified a need for a bottom-up strategy to heighten public awareness for the advanced development of GRGW to complement and prime the top-down mandatory installation policy.

Planning, Designing, and Managing Green Roofs and Green Walls for Public Health – An Ecosystem Services Approach

Installing green roofs and green walls in urban areas is suggested to supply multiple ecosystem services of benefit to human health and well-being. In a three-step literature review, we examined current knowledge on the link between public health and green roofs and green walls. A systematic search identified 69 scientific articles on green roofs/walls with a public health discourse. These articles were categorized according to type of health path covered (reduction of temperature, air pollution, noise or environmental appraisal) and coverage of issues of relevance for strategies on planning, design/construction, and maintenance of green roofs and green walls. Articles identified through the structured search were complemented with reviews (with no explicit public health rationale) covering reduction of noise, temperature, or air pollution and environmental appraisal. Other relevant studies were identified through snowballing. Several of the articles provided guidelines for optimizing the effect of green roofs/walls in supporting ecosystem services and maximizing well-being benefits to support health pathways identified. These included specifications about planning issues, with recommended spatial allocation (locations where people live, sun-exposed for maximum ambient temperature reduction) and with physical access needed for environmental appraisal. Recommendations regarding design parameters covered substrate depth (deeper generally being better), plant choices (more diverse roofs providing more services), and maintenance issues (moist substrate positively correlated with heat reduction).

Valuing ecosystem services of sustainable urban drainage systems: A discrete choice experiment to elicit preferences and willingness to pay

Sustainable urban drainage systems (SUDS) address stormwater management issues and provide a variety of benefits to residents in terms of ecosystem services. Economically valuing the non-monetary ecosystem services often proves difficult, as limited markets for SUDS measures exist, rendering revealed preference methods inapplicable. We conducted a discrete choice experiment to elicit the preferences and willingness to pay of the ecosystem services of SUDS in Berlin, Germany. Results from a latent class model indicated how residents weigh the different ecosystem services and that they garner the highest utility in improved water quality from reduced fish die-offs. With these results, practitioners and policy makers can better prioritize measures and make strong economic arguments for SUDS implementation and increasing the provision of ecosystem services.

Using Structural Equation Modeling to Examine Pathways Between Environmental Characteristics and Perceived Restorativeness on Public Rooftop Gardens in China

As a kind of informal green space more closely related to the built environment, public rooftop gardens (PRGs) are novel green open space and important salutogenic resource for urban residents. It is one of the most easily accessible method for urban residents to be in contact with outdoor or natural elements from the context of high-altitude living. Given its potential health benefits to city dwellers, existing empirical studies are heavily focused on immediate recovery through visually accessing PRGs (through windows), neglecting the possibility of using PRGs physically as a place of interaction. This paper hypothesizes usage patterns will mediate the associations between the environmental characteristics of PRG and users' restoration. This is done through inputting data from 12 typical samples of PRG in Chengdu, China into structural equation model (SEM). Combining the concept of Perceived Sensory Dimensions (PSD) and Perceived Restorativeness Scales (PRS) with the usage patterns of the above samples, this study aims to examine the correlation of environmental characteristics, usage pattern and restoration, in which identify their relative importance in the context of PRGs. Through serials of numerical tests on the model, the study shows that out of the 20 theoretical pathways constructed by the environmental characteristics (x)–usage patterns (m)–restorative effect (y), only 14 forms a significant correlation. In addition, out of all PSDs, social, serene, refuge, space and nature dimensions are induced into restorative effects through four patterns of use: retreat, nature touch, interpersonal interaction and family-bonding activities. The findings also show that social and family-bonding are the most influential independent and mediating variables respectively in achieving restorative effects in the PRG. This study reveals important findings about how usage patterns mediate the association between the PSD and PRS of users. And it also has generated practical implications on how we can design public rooftop gardens from the perspective of restoration, which could potentially be the key to the future survival and development of PRGs in urban environments.

Urban Integration of Green Roofs: Current Challenges and Perspectives

Green roofs (GRs) are a sustainable alternative to conventional roofs that provide multiple ecosystem services. Integrating GRs into urban areas is highly relevant considering the rapidly increasing built-up in cities. Therefore, this paper systematically and comprehensively reviews the recent literature from 2011 to 2019 on GRs to identify the challenges and perspectives related to the urban integration of GRs. The review suggests that the effectiveness of GRs in delivering ecosystem services is largely dependent on context-specific parameters such as weather conditions and existing construction or design-related parameters. Integrating GRs into urban areas can be challenging given the diversity of actors, functions, and conditions characterizing these areas. Although significant research has already been conducted on GRs, research covering more geographical locations and contexts is needed. The review points out the need to include future urbanization scenarios, such as tall buildings while analyzing the impact of GRs on ecological networks. Additionally, the review emphasizes the inclusion of urban morphological parameters alongside an analysis of the impact of GRs on microclimate regulation and air quality. In terms of social acceptance, this review points out the need to consider the temporal cycles of vegetation for noting users’ perspectives. Additionally, further research is required on the social impact of GRs, considering their influence on property prices. Lastly, the review stresses the need for more city-scale studies on the impact of GRs on ecosystem services.

Growth and Carotenoid Contents of Intercropped Vegetables in Building-Integrated Urban Agriculture

Sustainable food security due to climate and social change is more important than ever. This study was conducted to increase plant growth and bioactive contents using intercropping technology in urban agriculture. Tomatoes (Solanum lycopersicum L.) and sunflowers (Helianthus annuus L.) were intercropped in different ratios in outdoor rooftop, and lettuce (Lactuca savita L.) was grown with chicory (Cichorium intybus. L.) in the indoor LED plant growth chambers. Carotenoids in plant foods were analyzed using an ultraperformance liquid chromatography with photodiode array detection. Chlorophyll contents were determined by the soil analysis development chlorophyll meter. Tomatoes planted with sunflowers (3 : 1) had a significantly larger stem diameter ( $p<0.05$ ), a large number of leaves ( $p<0.05$ ), and significantly higher lycopene at d88 ( $p<0.05$ ), d102 ( $p<0.001$ ), and d115 ( $p<0.01$ ), and β-carotene contents at d102 ( $p<0.05$ ) as compared to those of monocultured tomatoes. Lettuce planted in a ratio of 1 : 3 with lettuce and chicory had significantly higher contents of chlorophyll ( $p<0.05$ ), β-carotene ( $p<0.05$ ), and lutein ( $p<0.01$ ), than lettuce planted alone. On the other hand, intercropping of chicory and lettuce did not have a beneficial effect on the growth and carotenoid content of chicory. The current study indicates that plant growth and carotenoid content can be substantially modified by cocultivation, and the effects may vary depending on the type of plant and the crop ratio.

Sustainable Urban Drainage Systems in Spain: Analysis of the Research on SUDS Based on Climatology

Sustainable urban drainage systems (SUDS), or urban green infrastructure for stormwater control, emerged for more sustainable management of runoff in cities and provide other benefits such as urban mitigation and adaptation to climate change. Research in Spain began a little over twenty years ago, which was later than in other European countries, and it began in a heterogeneous way, both in the SUDS typology and spatially within the peninsular geography. The main objective of this work has been to know through bibliographic review the state of the art of scientific research of these systems and their relationship with the different types of climates in the country. These structures have a complex and sensitive dependence on the climate, which in the Iberian Peninsula is mostly type B and C (according to the Köppen classification). This means little water availability for the vegetation of some SUDS, which can affect the performance of the technique. To date, for this work, research has focused mainly on green roofs, their capabilities as a sustainable construction tool, and the performance of different plant species used in these systems in arid climates. The next technique with the most real cases analyzed is permeable pavements in temperate climates, proving to be effective in reducing flows and runoff volumes. Other specific investigations have focused on the economic feasibility of installing rainwater harvesting systems for the laundry and the hydraulic performance of retention systems located specifically in the northeast of the Iberian Peninsula. On the contrary, few scientific articles have appeared that describe other SUDS with vegetation such as bioretention systems or green ditches, which are characteristic of sustainable cities, on which the weather can be a very limiting factor for their development.

Analyzing the Impact of Green Roof Functions on the Citizens' Mental Health in Metropolitan Cities

Background:

The fast-growing trend of urbanizations and the dwellers’ stressful lifestyle in megacities has led to several drawbacks from the mental health perspective. Provided that there is a significant association between the green environment and mental health, we investigated different functions of a green roof from two perspectives of well-being and environment.

Methods:

After investigating on different functions of the green roof and classifying them into two sections, a self questionnaire survey was conducted in May 2020 on 100 citizens of the Seoul metropolitan area after, South Korea visiting the green roof. They were asked to clarify their perception of the different functions of green roof gardens. The statistical analysis was performed to show the differences in perception and how each variable can contribute to such differences.

Results:

The results illustrated a high satisfaction rate among the visitors of green roofs. The perception of the well-being functions was higher than those of environmental functions. However, age group can alter the perception significantly, as the senior citizens significantly perceived the well-being functions. In contrast, the awareness of the environmental functions was higher among the younger participants.

Conclusion:

Providing practical information about the ideal functions of green roofs, this study offered helpful insight for the planners who focus on society’s general health and work in two different sections: developing the city landscape and mental health improvement.

Users’ Perceptions of Green Roofs and Green Walls: An Analysis of Youth Hostels in Lisbon, Portugal

Green roofs and green walls are a potential strategy to increase green spaces in the urban environment. These solutions bring multiple benefits to the cities at the economic and socio-environmental levels. However, from the point of view of private investors, green roofs and green walls often have a negative financial evaluation. Concerning this, the quantification of the benefits according to building use and occupancy could be an important tool to assist the decision-making process and guarantee returns on investment. This study aims to support the decision-making process by managers and owners of youth hostels regarding green roofs and green walls implementation. Using a structured questionnaire, users’ perceptions were assessed through a five-point Likert scale. The survey was conducted in five youth hostels in Lisbon, Portugal. Analyses were performed in two phases. Firstly, using the original sample (n = 345), and subsequently grouping homogeneous individuals through cluster analysis. The results showed that most respondents support green infrastructure installation in the hostel and consider that these solutions could provide a greater sense of individual well-being and local aesthetic improvement. However, there is no strong evidence that green infrastructure solutions are considered a deciding factor to select local lodging, despite the fact that it can be a tiebreaker factor between two similar options. Furthermore, findings have shown that 90% of the respondents from Cluster 1 and 92% from Cluster 4 are probably not willing to pay higher daily rates for youth hostels that have green infrastructure solutions in place. On the other hand, 67% of the respondents from Cluster 2 were potentially willing to pay an additional amount. For the 345 respondents, the most preferred green infrastructure typologies are indoor living wall and the accessible green roof. Moreover, findings support the gender socialization and identity theory showing that women have a greater environmental concern compared to men.

Green-Roof: The Role of Community in the Substitution of Green-Space toward Sustainable Development

The research challenge in the problem of the sustainable development goals is to find solutions for development control through the application of green roofs in residential areas, which is the feasibility of the role of the community. This research was based on the discipline of architecture by considering the role of the community in managing architectural green-space substitution. The purpose of this study was to identify patterns of the role of the community for green roofs feasibility based on housing, conducted in some parts of Sumatra, Java, and East Nusa Tenggara, Indonesia. Data were collected using a survey questionnaire. Data were calculated based on percentages and analyzed using the chi-square method. The results indicated that the optimization of the community role was needed for the sustainability of the green-roof from all economic levels, both urban and rural. The aspect of public awareness and knowledge of the benefits of the green-roof is very high, but the object of the green-roof in Indonesia is still very limited because participation is still not optimal. Therefore, it is necessary to promote the green-roof application to the community by adapting local culture in sustainable green-roof technology innovation.

Green roof perceptions: Newcastle, UK CBD owners/occupiers

Purpose

The purpose of this paper is to explore perceptions of the advantages and disadvantages of green roofs for commercial real estate building owners/occupiers in a UK city and consider how these might affect the chances of their adoption.

Design/methodology/approach

Two sets of semi-structured interviews were conducted with purposively selected respondents, 10 with and 25 without green roofs, to compare and contrast differing perspectives. A grounded theory approach was taken to data analysis, allowing themes to emerge directly from the data.

Findings

Low awareness and understanding were observed amongst those without green roofs, which positively affected perceived costs whilst negatively affecting perceived benefits. Green roof owners gave weight to wider societal and ecosystem services benefits, whilst those without focussed much more upon building-level benefits and costs.

Research limitations/implications

Because of the restricted sample size, the findings in themselves are not generalizable; rather, themes are drawn from the research for reflection.

Practical implications

Findings point to steps that might be required of regional and national government to increase green roof uptake. This could involve initiating conversations to raise awareness, shift discourse and perceived norms and best practice; offering incentives, education and training; and presenting high-profile exemplar projects of green roofing to begin to mainstream the technology and get it onto the radar of building owners.

Originality/value

Bringing together social research around cohorts with and without green roofs, the paper throws into sharp relief discussions around costs and benefits and points towards potentially more productive directions for action to encourage consideration and take-up of green roofs by building owners.

Perception and Barriers to Implementation of Intensive and Extensive Green Roofs in Dhaka, Bangladesh

Buildings are one of the biggest consumers of fossil fuels, and thus, contribute largely to greenhouse gas emissions. As a result, a large number of studies have been conducted and innovative ideas or green solutions have been invented, adopted, and implemented across the globe. These solutions are often contextual and heavily dependent on local environmental and socio-economic factors. Green roofs are such an example. Green roofs (both intensive and extensive) for buildings have been successfully adopted in many countries around the world. Bangladesh, a developing country that can benefit from green roofs, seems to remain in complete darkness regarding its potential. The objective of this study is to identify the reasons why green roofs have not been widely implemented in Bangladesh, especially in the capital Dhaka, even though, theoretically, the climatic conditions of this country favor this technology. This study focuses on the perception of the construction industry to comprehend the possible obstacles they are facing towards using green roofs in their designs. A questionnaire study was conducted among architects, engineers, construction managers, contractors, and owners who are at different levels of experience in their respective fields. The results indicate a gap in knowledge and misconceptions, which are major hindrances to the implementation of green roofs.

Greywater recycling in buildings using living walls and green roofs: A review of the applicability and challenges

Living walls and green roofs offer numerous benefits to densely populated urban areas such as cooling, air filtering and improved aesthetics. However, plants in these two systems are high water consumers making such systems particularly unsuitable for water-scarce arid environments most at need of passive cooling and urban greening. Integrated greywater treatment in these structures provides a possible solution, providing plants not only with water but other required nutrients and organics. However, greywater treatment by living wall and green roof systems is still lacking. This review summarizes the few studies exploring this new integrated technology and provides an in-depth analysis of existing literature on vegetated building structures and greywater treatment to reveal benefits and potential pitfalls of this technology. Appropriate selection of plants and media are essential to successful system design and must meet competing demands compared to those used in existing vegetated building structures for cooling/greening and constructed wetlands for greywater treatment. A variety of operational and user-interaction issues are also explored and will be key areas of future research to enable full-scale implementation. Integrated greywater treatment using green building vegetated structures appears a promising method for dual purpose water recycling and urban cooling, and various future research needs are emphasized to realize this.

Spontaneous dynamics and wild design in green roofs

Green roofs and other constructed environments represent novel ecosystems, yet have potential to contribute to biodiversity conservation goals. Constructed ecosystems are intentionally managed to produce specific services, and thus could be viewed as highly artificial or controlled. Yet all constructed ecosystems exhibit spontaneous dynamics, as community structure changes due to internal or external ecological processes. While all green roofs have some element of design and human control over ecological trajectories, the level of ongoing management can vary greatly. I discuss “wildness” as a characteristic of green roofs in response to their spontaneous dynamics after initial setup, and their potential to provide ecosystem services related to human psychological well-being, aesthetics and habitat for biodiversity. This approach suggests new design possibilities in interaction with spontaneous ecosystem dynamics and highlights a need for greater ecological understanding of green roof systems.

Developing resilient green roofs in a dry climate

Living roofs are an emerging green infrastructure technology that can potentially be used to ameliorate both climate change and urban heat island effects. There is not much information regarding the design of green roofs for dry climates and so the aim of this study was to develop low maintenance and unfertilized green roofs for a dry climate. This paper describes the effects of four important elements of green roofs namely slope, depth, growing media and plant species and their possible interactions in terms of plant growth responses in a dry climate. Sixteen medium-scale green roofs were set up and monitored during a one year period. This experiment consisted of twelve vegetated platforms and four non-vegetated platforms as controls. The design for the experiment was a split-split-plot design in which the factors Slope (1° and 25°) and Depth (100mm, 300 mm) were randomized to the platforms (main plots). Root depth and volume, average height of plants, final dry biomass and ground cover, relative growth rate, final dry shoot-root ratio, water use efficiency and leaf succulence were studied during a twelve month period. The results showed little growth of the plants in media type A, whilst the growth was significant in both media types B and C. On average, a 90% survival rate of plants was observed. Also the growth indices indicated that some plants can grow efficiently in the harsh environment created by green roofs in a dry climate. The root growth pattern showed that retained water in the drainage layer is an alternative source of water for plants. It was also shown that stormwater can be used as a source of irrigation water for green roofs during six months of the year at the study site. In summary, mild sloping intensive systems containing media type C and planted with either Chrysocephalum apiculatum or Disphyma crassifolium showed the best performance.