Is greening the building envelope economically sustainable? An analysis to evaluate the advantages of economy of scope of vertical greening systems and green roofs

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.     

Public views on green roofs and green walls in two major Asian cities and implications for promotion policy

Public views on green roofs and green walls (GRGW) have received little attention; hence, related policies could be detached from community needs and expectations. A comprehensive questionnaire was developed to compare perceptions of GRGW benefits and negative impacts and attitudes towards government GRGW promotion in Beijing and Hong Kong. Beijing residents reported stronger positive perceptions of benefits, weaker perceptions of negative impacts, and greater support to promotion measures. Beijing’s more proactive and effective promotion efforts brought a better-informed citizenry with positive outlooks. Both cities appreciated promotion policies and strongly preferred advocating for GRGW quality. Public views were subsumed under three underlying factors: socio-demographic, living-environment, and greening-attitude. Principal component analysis and multiple linear regression detected city-dependent relationships between factors and perceptions. Senior and less-educated respondents in Beijing were less able to perceive the negative impacts. Younger and well-educated respondents in Hong Kong held a strong greening attitude and better recognition of benefits. GRGW perceptions were robust predictors of attitudes towards promotion policies in both cities. The implications for GRGW development vis-a-vis a city’s socio-cultural context were discussed. The findings could help governments hone the publicity and policy aspects of GRGW promotion and development and fine-tune greening programmes to citizen preferences.     

The impact of urban green infrastructure as a sustainable approach towards tropical micro-climatic changes and human thermal comfort

Green infrastructures such as living walls are technological solutions to replace the declined greenery at urbanized environment and also reliable applications for thermal regulation in buildings through insulation effect and escalates the energy use efficiency. Thermal comfort and local climate are spatiotemporally variable. The existing research gap should be addressed by evaluating the performance of vertical green walls in tropical condition. In this study, thermal performance, relative humidity (RH) and CO₂ concentration were quantified for basic three types of green infrastructures; such as (T₁) living walls, (T₂) indirect green façades and (T₃) direct green façades located in Colombo metropolitan in Sri Lanka. An in-situ experimental study was conducted considering temperatures at 1 m and 0.1 m distance in front of the green walls, inside the foliage, air gap and external wall surface comparatively to adjacent bare wall control. Three case studies per green infrastructure within Colombo metropolitan area were purposively selected. Simultaneously, RH and CO₂ concentration at 0.1 m in front of the green and bare walls were measured for the performance quantification. The internal thermal comfort simulation and occupants’ satisfaction questionnaire survey was executed to assess the green infrastructure performances. The study revealed that vertical greenery systems were highly effective on external wall surface temperature reductions at 1100 h–1500 h time zones. T₁ and T₂ accounted for superior temperature reduction in the range of 1.61 °C–1.72 °C through the façade relative to the distance than T₃. Maximum temperature reduction compared to the bare wall control was obtained for the T₁ (0.28 °C–8.0 °C) followed by T₂ (1.34 °C–7.86 °C) and T₃ (1.34 °C–6.64 °C). Averaged RH increment (1.6%–1.81%) and CO₂ reduction (0.63%) occurred near green walls at day time compared to control. An average 28 °C simulated indoor temperature circumstantiate the indoor thermal comfort. 58% and 89.5% occupants’ were satisfied with thermal and visual comfort respectively, thus emphasizing façade greening as a sustainable approach on micro climatic changes and human thermal comfort.     

周口市立体绿化方式研究

立体绿化是丰富城市景观、改善城市环境的好方法.通过对周口市主要立体绿化形式的调查,发现墙体绿化和棚架廊柱绿化较为常见,而屋顶绿化和河道边坡绿化仍有很大发展空间.     

Bioreceptivity of living walls: Interactions between building materials and substrates,and effect on plant growth

Bringing nature into urban areas is largely recognized as one of the multiple benefits of green walls. Among the existing types of living walls, those made from durable building materials have a longer lifespan and require less maintenance than many typical green wall systems. In that context, there is a need to study the bioreceptivity of materials, i.e., their ability to host living organisms. This paper presents a novel method to study the bioreceptivity of materials, by enhancing the biological and physicochemical exchanges in different mixtures of crushed materials and substrates, and by measuring their effect on plant growth. For this experiment, we crushed and sieved four different building materials (3 types of concretes and 1 brick) to increase their contact surface. We then mixed them with substrate with or without compost additions. The mixtures were used as growing media for the cultivation of two wild mural plant species in a glasshouse. Plant growth and the physicochemical evolution of the mixtures were monitored for one year. The study shows the physical and chemical differences between the building materials, their interactions with substrate composition, and their effect on plant growth. Two main results appeared: (i) high pH (>8) was the major constraint against plant growth (ii) compost additions significantly compensated for adverse characteristics of the materials. Assuming that higher plant growth is associated with better bioreceptivity, this experiment introduces a quantitative method that could contribute to the evaluation of the agronomic properties of building materials. The results allow us to make recommendations for Living wall and Technosol design.     

Biological potential in cities: An estimate from Melbourne

Despite the many benefits of vegetation in urban settings, inner-city areas often are sparsely vegetated or devoid of plants. This suggests substantial opportunity for improving provision of ecosystem services in densely populated areas, through retrofitting of urban environments with plants. This paper introduces the concept of ‘biological potential’ – the pragmatic potential for urban areas to be retrofitted with suitable green infrastructure.This paper demonstrates a method for making a quantitative, spatially explicit estimate of the biological potential of walls in the CBD of Melbourne, Australia. The results of this study represent an estimate of how much wall space could be home to green façade plants (i.e. creepers and climbers). The methodology is also spatially explicit – it estimates where the best locations in the city are for this kind of greening, recognising that not all walls have suitable physical characteristics or local microclimates. Employing a combination of GIS and microclimatic modelling techniques, this study estimates that over 16 ha of wall space has potential for greening in Melbourne's CBD, with 1.8 ha showing optimal characteristics.     

Vegetation establishment on ‘Green Walls’: Integrating shotcrete walls from road construction into the landscape

The establishment of a sustainable vegetation layer on shotcrete walls subjected to road environment represents enormous challenges. High inclination of almost 90°, the exposed position of the walls near streets as well as lack of soil and water supply pose major limiting conditions. The objective of this study was to evaluate the performance of an innovative greening technology for vertical structures in terms of vegetation development on varying plant substrates and geotextiles.The field experiment included testing three plant substrates on basis of nearby rocky excavation material (‘Innsbrucker Quarzphyllit’, ‘Bündnerschiefer’ and ‘Zentralgneis’) combined with compost. Additionally, five geotextiles (geogrid (3x4 mm), geogrid (9x10 mm), coir net, coir mat, geo mat) were applied for assessment. All test combinations were evaluated regarding vegetation cover, species composition, and biomass production from 2015 to 2016. Analyses of chemical properties were conducted for all plant substrates.Results showed highest vegetation cover ratio on ‘Bündnerschiefer’ and ‘Innsbrucker Quarzphyllit’, which can be explained by the favorable mineral composition (nutrient storage capacity) and chemical properties of compost (lower values of electrical conductivity and C/N ratio).In conclusion, the use of ‘Green Walls’ filled with ‘Bündnerschiefer’ or ‘Innsbrucker Quarzphyllit’ plant substrate in combination with netlike geotextiles like geogrid or coir net proved best. They are promising in terms of establishing an optimal vegetation cover on vertical structures and are well suited for integrating shotcrete walls into the landscape. The use of local excavation material for greening purposes thus can be confirmed. Though, the use of high-quality compost is crucial.     

Artificial lawns: Environmental and societal considerations of an ecological simulacrum

The replacement of living lawns with synthetic (plastic) grass seems to be on the increase in cities. This paper presents some environmental and societal considerations relating to the installation of artificial lawns to encourage research of the phenomenon at this early stage of emergence. After first discussing the development of ‘third generation’ synthetic grasses that have made artificial lawns more appealing, it then considers how the replacement of living lawns with plastic grass represents a potentially concerning step towards ecological simulation, or the replacement of real ecosystems with simulacra that address cultural desires but remove nature altogether. The paper then examines some of the possible environmental and societal impacts that may result from the replacement of living lawns with their artificial counterparts, and concludes with the presentation of a research framework for investigation of the emerging artificial urban lawnscape.     

How climate change perception is reshaping attitudes towards the functional benefits of urban trees and green space: Lessons from Hong Kong

Urban greening has rapidly emerged as a key urban climate change adaptation strategy. Urban greening is thought to confer manifold socio-ecological benefits upon residents in towns and cities. Yet proponents of urban greening have seldom considered how people’s support for greening policies may be shaped by weather and climate. This paper reports the results of exploratory research examining public expectations of adverse weather changes and people’s attitudes toward the functional benefits of urban trees and green space. Results of a questionnaire survey of 800 residents of Hong Kong indicate a positive relationship. Respondents tended to rate functional benefits as more important if they anticipated adverse weather changes in the near future, namely, rising temperatures, more tropical cyclones and prolonged rain. This subjective weather effect is more salient when these weather changes are perceived as a threat to one’s daily life. We found urban greenery is assigned a higher value by individuals concerned about exposure and vulnerability to climatic stressors. Affinity for greening appears to be related to how weather and climatic variability is perceived. This observation is informed by a broader geographic perspective, which construes weather and climate as part of the spatial environment in which urban nature is apprehended and comprehended. An explanation for our findings is that increasingly volatile weather can potentially reshape urban residents’ interactions with nature, based on perceived relief and/or protection from climate-related threats.     

Against the wall—Root growth and competition in four perennial winter hardy plant species grown in living walls

Plants in living walls face challenges from intraspecific and interspecific competition from plants around them, as well as water and nutrient availability in the growing media. This paper explores these challenges using four different species of hardy perennials.Campanula poscharskyana ‘Stella’, Geranium sanguineum ‘Max Frei’, Sesleria heufleriana and Veronica officinalis ‘Allgrün’ were grown in two types of vertical growing media, made of either coir or stone wool, in transparent boxes under greenhouse conditions. In the media, plants were placed above each other, two plants of same species, two plants of different species, or a plant grown alone. Root frequency was registered over 56 days and the activity of individual root systems was studied through uptake of ¹⁵N. In addition, plant dry weight and N content as well as water content in the growing media were measured at cessation of the experiment.Shoot and root growth as well as nutrient content in plants were higher in coir than in stone wool and plants placed at the top position had significantly higher biomass than at the bottom position. The stone wool media had significantly higher water content in the lower part of the media while the coir media had water more evenly distributed. Species differences in root frequency were found. Campanula and Geranium showed strong root growth and had root frequencies of up to 0.9, whereas Sesleria and Veronica had less root growth, in some cases only root frequencies around 0.3. The species reacted differently to root competition and planting position and there were differences in the competitive ability between the species. Campanula and Geranium were not affected by competition, whereas both Veronica and Sesleria showed altered root growth due to competition depending on the growing medium. When Geranium was grown above Veronica in stone wool, plant biomass and ¹⁵N uptake increased in Veronica indicating environmental modification, with one species improving the growing conditions for another.The results revealed that growing plants vertically in a living wall is complex, and that choice of growing medium and species composition is important for a successful living wall. Planting combinations should therefore be tested before being used in commercial applications.     

Exploring the use of edible and evergreen perennials in living wall systems in the Scandinavian climate

We have performed a field experiment to investigate the survival and vitality of perennial plants in a living wall installed in an industrial area in Malmö, southern Sweden. The main aim of the study was to investigate the possibility of growing edible and evergreen perennial plants in living wall systems in the Scandinavian climate. We conclude that the edible perennial plants Allium schoenoprasum, Calamintha nepeta, and Fragaria vesca are feasible in living wall systems in the Scandinavian climate. Thymus vulgaris is sensitive to the Scandinavian climate, and performed equally poorly in Rockwool panels and in soil-filled containers (controls). We also conclude that the evergreen perennial plant species Chamaecyparis pisifera, Euonymus fortuneii, Euphorbia polychroma, Vinca minor, and Waldsteinia ternata can be grown in green walls, and that the edible evergreen plant Vaccinium vitis-idea is highly suitable for living walls in this climatic region. A. schoenoprasum, C. pisifera, E. fortuneii, I. crenata, L. sylvatica, V. minor, and V. vitis-idea showed 100% survival rates, however, the visual quality of e.g. I. crenata and L. sylvatica was not acceptable for ornamental purposes.     

蓄热水管对日光温室温度环境的影响

以内保温日光温室为研究对象,在日光温室后墙(37墙)加装间距0.4 m的水管(直径0.1 m、长3 m)共28根,蓄热水管总体积0.66 m~3,研究蓄热水管对日光温室热环境的影响。结果表明:日光温室加装蓄热水管后,晴天时温室内最低气温可提高2.3℃,阴天时提高0.6℃,后墙距墙体内表面0、10、20 cm处最低温度均高于对照,墙体的保温性能明显增强。1月试验区最高气温、最低气温及平均气温分别提高了5.22、0.71、1.36℃。连续不良天气(3 d)条件下,加装蓄热水管能将日光温室土壤(20 cm)日最低温提高2.6~3.1℃;连续晴天(3 d)条件下能提高2.0~3.7℃。可见,加装蓄热水管明显地改善了温室内的热环境,提高了日光温室的太阳能热利用率。     

The economic benefits and costs of trees in urban forest stewardship: A systematic review

Understanding the benefits provided by urban trees is important to justify investment and improve stewardship. Many studies have attempted to quantify the benefits of trees in monetary terms, though fewer have quantified the associated costs of planting and maintaining them. This systematic review examines the methods used to jointly analyse the costs and benefits of trees in the urban landscape, assesses the relative balance of benefits and costs, and attempts to understand the wide variation in economic values assigned in different studies. The benefits most frequently studied are those related to environmental regulation and property values, and the available data show that these usually outweigh the costs. Aesthetic, amenity, and shading benefits have also been shown to provide significant economic benefits, while benefits in terms of water regulation, carbon reduction and air quality are usually more modest. Variation in benefits and costs among studies is attributed largely to differences in the species composition and age structure of urban tree populations, though methodological differences also play a role. Comparison between studies is made difficult owing to differences in spatiotemporal scope, and in the way urban forest composition and demographic structure were reported. The overwhelming majority of studies concern deciduous trees in Northern America, and much less is known about urban forests in other regions, especially in the tropics. Future work should thus seek to fill these knowledge gaps, and standardise research protocols across cities. In light of ambitious goals in many cities to increase tree cover, ongoing advances in valuation methods need to provide a more comprehensive accounting of benefits and costs, and to better integrate economic assessment into the decision-making process.     

Can we integrate ecological approaches to improve plant selection for green infrastructure?

Modern cities are dominated by impervious surfaces that absorb, store and release heat in summer, create large volumes of runoff and provide limited biodiversity habitat and poor air quality can also be a health issue. Future climate change, including more frequent and extreme weather events will likely exacerbate these issues. Green infrastructure such as parks, gardens, street trees and engineered technologies such as green roofs and walls, facades and raingardens can help mitigate these problems. This relies on selecting plants that can persist in urban environments and improve stormwater retention, cooling, biodiversity and air pollution. However, plant selection for green infrastructure is challenging where there is limited information on species tolerance to heat and water variability or how these species can deliver multiple benefits. Therefore, we draw on research to illustrate how plant performance for green infrastructure can be inferred from plant attributes (i.e., traits) or from analysis of their natural distribution. We present a new framework for plant selection for green infrastructure and use a case study to demonstrate how this approach has been used to select trees and shrubs for Australian cities. We have shown through the case study and examples, how plant traits and species’ natural distribution can be used to overcome the lack of information on tolerance to both individual and multiple stressors; and how species contribute to the provision of benefits such as stormwater retention, cooling, biodiversity and air pollution mitigation. We also discuss how planting design and species diversity can contribute to achieving multiple benefits to make the most of contested space in dense cities, and to also reduce the risk of failure in urban greening.     

Greening urban road verges highlights diverse views of multiple stakeholders on ecosystem service provision,challenges and preferred form

Globally, there is growing recognition of the potential of road verges to contribute to urban greening and ecosystem service provision, beyond their original functions of utility provision and public access. Numerous, diverse stakeholders are involved in their management, yet their shared and diverging perspectives on verge greening are poorly understood. This research examined the perspectives on road verge greening by 30 respondents from eight stakeholder groups from the Perth Metropolitan Area, Australia. Stakeholders spanned local and state governments, developers, peak bodies, utility providers, environmental consultants, verge treatment providers and urban greening advocates. Semi-directed interviews and Likert scales were used to assess respondents' perspectives and perceived importance of urban verge functions and ecosystem services, risks and challenges associated with verge greening, and preferred verge vegetation composition. The most important ecosystem services for all stakeholders were temperature regulation (through the provision of street trees), those associated with water management and aesthetically interesting streetscapes. Perceived challenges included limited knowledge for the management of native species verges and streetscapes, organisational costs for verge managers and utility providers, and the need to engage with multiple local government authorities with widely varying management and financial valuation of verge vegetation. Stakeholders’ preferred verge reflected diverse uses, local characteristics, and was climate and water resilient (particularly ‘waterwise’). A majority of stakeholder groups felt greater attention to the ‘understorey’ of the ‘urban forest’ was warranted. An emerging perspective across four stakeholder groups identified the potential for verges to grow a local ‘sense of place’, through plantings emphasising local native species and highlighting local Whadjuk Noongar seasons. These findings support policies and programmes associated with urban greening, and assist in navigating the contestation often associated with new or transformative uses of land at the public-private interface.     

“A living street and not just green”: Exploring public preferences and concerns regarding nature-based solution implementation in urban streetscapes

Leveraging the benefits offered by nature-based solutions (NBS) will be vital in addressing present and future environmental and social challenges as urban densification continues to exert pressure on cities. The greening of urban streets, in particular, provides many benefits in terms of livability, health, and biodiversity. While many studies have explored the suitability of NBS in a particular context considering the benefits they provide in relation to local environmental challenges (e.g. filtering the air in areas with high pollution, absorbing water in areas prone to flooding), this study focuses on residents’ perspectives on and their demand for NBS. This is particularly relevant given the importance of public acceptance of NBS measures for their success. The research presented in this paper is based on a mixed-methods study, combining an online survey and eight focus group interviews, which aimed to better understand which types of NBS people prefer, how much and what types of street space they are willing to exchange for street greening, and the opportunities and concerns they have regarding varying degrees of street greening. Findings suggest that respondents are overwhelmingly in favor of greening their street with NBS, yet preferred NBS and opinions on where to implement them vary among participants. Further, street greening was thought to come up against other understandings of how streets should be used and for what purpose. These considerations should be taken up by planners to improve the uptake of NBS.     

垂直绿化在城市绿化中的应用与管护

随着经济的发展和社会的进步,城市人口增多、建筑密度变大、用地紧张,垂直绿化成为城市绿化发展的一个重要方向.文章介绍现代城市建设中垂直绿化的应用,总结城市垂直绿化中常用的植物种类、应用形式和管护技术.     

The Nature Smart Cities business model: A rapid decision-support and scenario analysis tool to reveal the multi-benefits of green infrastructure investments

Incorporating natural spaces within urban areas has been shown to have multiple benefits. However, despite greening and adaptation strategies at different levels of government, progress remains slow with a lack of easy to use and comprehensive tools identified as key to overcoming this. This paper presents a co-designed tool with academic and local authority partners to demonstrate the ecosystem service benefits of small-scale urban green infrastructure projects. Through the tool, users can readily assess the impact of green infrastructure investments on the delivery of a selection of ecosystem services in the early stages of a project. Furthermore, the tool provides a standardised assessment of cultural ecosystem services’ contributions, as well as offering a method to score spatial designs on the impact on habitat for biodiversity. Use of the tool is demonstrated using a pilot study in Kapelle, the Netherlands. The results set out an overview of the impacts of the spatial design on estimated ecosystem service delivery. They also show the tool’s potential to add value in early project stages and as a planning and design tool, helping to maximise the benefits that can be achieved through green infrastructure design. Complementing these arguments with ball-park estimations on green infrastructure costs, the Nature Smart Cities Business Model aims to offer public sector officers the means to create a business case for green infrastructure measures, facilitating the translation from strategies to actual plans, thus benefitting green infrastructure implementation in the public realm.     

滨海城市盐碱地园林绿化技术探讨

随着国民经济和社会的迅速发展,人口增长与耕地减少的矛盾日益突出,各类盐土资源,特别是我国海岸带盐土作为一种重要的土地后备资源,亟待去开发、利用和保护.现针对滨海盐碱地区土壤条件苛刻,土地生产力低,难于建立植被,严重制约这些地区园林绿化的质量和数量等问题,在原有滨海城市盐碱地园林绿化技术的基础上,通过物理措施、工程措施、化学措施、生物措施等改良盐碱地土壤环境并结合选择耐盐植物,为这一地区盐碱地改良及城市绿化提供适宜的树种和技术标准,丰富沿海地区园林树种,增加树种多样性,改善沿海发达地区的生态环境和投资环境,为我国东部沿海地区园林绿化成活率提供重要保障.     

Alterations in use of space,air quality,temperature and humidity by the presence of vertical greenery system in a building corridor

Urban greenery is valued not only for its aesthetic value but also for environmental services and the overall health benefits that follows. A large portion of the world population now resides in built environments, and there is growing need to provide a conducive and healthy environment for the dwellers. Vertical greenery systems (VGS) provide greenery opportunities in cities even when there is limited land space especially as recent technology enables people to grow plants outdoors as well as indoors. Indoor vertical greenery (iVGS) was installed to monitor any alteration in the temperature, humidity, particulate matter and use of space. The present study used an actual environment, included paralled corridors in the same building. The movement in both corridors were significantly (p < 0.05) correlated and post green wall establishment data showed the relationship changed significantly (r² = 0.8748, P < 0.0001, RMSE = 23.4521) with relatively more people using the corridor after the iVGS installed. Significant difference was seen in the humidity levels but not in the temperature after the installation. Particulate matter levels dropped 48.5%, 82.6%, 5.5% (PM2.5, PM10,>PM10 respectively) in the corridor with iVGS by the end of the data collection. These findings suggest larger green coverage would have a greater positive impact on the environmental conditions of an indoor environment.