Green / living walls

Living walls: substrate-based, interior.  Source: Sydchrismom, CC BY 4.0, wikimedia commons..

Green walls (green façades or living walls) are strategies that involve the vertical greening of building surfaces using plants. These walls can be installed both indoors and outdoors in new-build or some retrofit situations, adding vegetation to urban environments or enhancing interior spaces. Green walls are often used for aesthetic enhancement, air purification (Feng, & Hewage, 2014), thermal performance enhancement of buildings (Cuce, 2017), and biodiversity support (Chen et al., 2020). See also vegetation-integrated buildings and green roofs.

Green walls

Green walls can be implemented in various locations, including urban, peri-urban, and rural settings. Urban areas often face challenges like heat islands, pollution, and limited green spaces. Green walls are highly suitable for urban areas in Te Moananui Oceania because they help mitigate the urban heat island effect, improve air quality, reduce energy consumption in buildings, and enhance biodiversity in otherwise concrete-dominated environments.

Peri-urban areas typically have a mix of urban and rural characteristics, with some agricultural or natural spaces interspersed with residential or industrial developments. Green walls can also be beneficial in peri-urban areas by maintaining ecological connectivity, providing habitat for wildlife, and contributing to local food production through vertical farming.

Rural areas in Oceania are characterised by agricultural lands, small communities, and natural landscapes. They may face challenges related to soil erosion, biodiversity loss, and climate change impacts. While green walls are less common in rural settings, they can still have some applications. For instance, they can be used in buildings or community centres to promote sustainable practices, provide insulation, and integrate with local ecosystems.

There are two main types of green walls classified based on their growing methods (Coma et al., 2017). These are Green façades and Livign walls. Each have several sub-categories.

Green façades refer to vertical surfaces of buildings covered with climbing plants or vines. The plants may be self-clinging or require additional support. Green façades typically use trellises, cables, or mesh structures to support climbing plants. They may be ground-based (plants grow directly out of the soil around the building), or container-based (plants grow out of containers placed at different levels up a façade). Green façades offer benefits such as thermal insulation, noise reduction, and habitat creation while enhancing the building’s façade with greenery. The three green façades sub-categories follow.

Green façade: direct climbing is a vertical greening system (VGS) where plants, typically vines or climbing plants, directly attach themselves to a building’s façade without the need for additional support structures.

Green façade: indirect climbing. In this VGS, climbing plants are supported by additional structures such as trellises, cables, or mesh panels attached to the building’s facade.

Green façade: hanging gardens. In this VGS, plants are suspended or hung from the building’s façade, creating a cascading effect of greenery.

Living walls

Living walls consist of a framework or support system attached to a vertical surface that holds the plants and provides the necessary structure for their growth. They can be soil-based or hydroponic and may incorporate a variety of plant species with plants grown in containers attached to a wall (Bustami et al., 2018). They may also use modular systems with pre-grown plant panels. The two living walls sub-categories follow.

Living walls: hydroponics. Hydroponic living walls are a soil-less method of growing plants where nutrient-rich water is used as the medium to provide essential nutrients. It involves growing plants directly in a nutrient solution or an inert medium such as expanded clay pellets, rockwool, or foam.

Living walls: substrate-based. In substrate-based living walls, vegetation relies on a growing medium or substrate to support plant growth. It is typically constructed using a modular frame, panel system or textile bags that holds the substrate and plants in place. These living walls can be used in exteriors or interiors and can accommodate a variety of plant species.

There are other types of green walls classified based on their function or specific benefit they provide:

Vertical farms / façade farming / produce walls: These involves the cultivation of plants on the exterior façades of buildings by employing various growing techniques, such as container gardening, vertical planters, or modular systems. See: vertical farms/facade farming.

These vertical farms can also be installed in the interior of a building. These are the indoor agricultural systems that use vertical stacking or tiered platforms to grow crops in a controlled environment. These farms often utilise hydroponic, aeroponic, or other soil-less growing methods to maximise space and optimise resource use.

Bio-shading walls. These walls utilises living vegetation to create shade and mitigate direct solar radiation reaching building interiors. They typically consist of a framework or panel system that supports plant growth.

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Name of NbS

Green / living walls

Type of NbS

Hybrid living/engineered interventions; Created or constructed living ecosystem

Location

  • Urban
  • Peri-urban
  • Rural
Exterior vertical farm. Source: Lufa farms, CC BY-SA 2.0, wikimedia commons.

Relationship to Indigenous knowledge

Many Indigenous cultures in Te Moananui Oceania, such as the Māori in Aotearoa New Zealand or various Pacific Island communities, have rich traditional knowledge about plants, ecosystems, and sustainable land management practices (Hikuroa, 2017). The design of green walls can draw inspiration from these Indigenous knowledge systems, incorporating native plant species and cultivation techniques that have been historically used to practice kaitiakitanga (environmental stewardship) (Harmsworth and Awatere, 2013). The concept of biophilic design, which seeks to connect people with nature in the built environment (Kellert, 20023), often aligns with Indigenous perspectives on the interconnectedness of humans, plants, and the natural world (Lee-Hammond, 2017).

Climate change benefits
  • Biomass cover loss
  • Increased temperatures
  • Loss of food production
  • Reduced air quality
  • Reduced water quality
  • Urban heat island effect

Green walls enhance urban resilience and adaptation capacity to climate-related challenges. Green walls create more liveable and climate-resilient cities, improving the quality of life for residents. They contribute to community well-being, safety, and long-term sustainability in the face of climate change impacts.

Urban areas experience the heat island effect, where built surfaces absorb and retain heat, leading to higher temperatures compared to surrounding natural areas. Green walls help to mitigate the heat island effect by providing natural cooling through evapotranspiration. Plants absorb sunlight, release water vapour, and create a cooler microclimate around buildings. Reduced heat island effect contributes to climate resilience by decreasing energy demand for cooling, improving outdoor comfort, and reducing heat-related health risks in urban environments (Price et al., 2015).

Increased energy consumption for air conditioning and cooling in buildings is driven by climate change related rising temperatures. Green walls act as natural insulation, reducing the need for mechanical cooling systems. They can lower indoor temperatures, decrease energy use, and contribute to energy efficiency in buildings. Reduced energy consumption leads to lower greenhouse gas (GHG) emissions associated with electricity generation, contributing to climate change mitigation efforts (Pérez et al., 2014).

Air pollution and GHG emissions from vehicles, industries, and urban activities contribute to poor air quality and health hazards. Green walls filter airborne pollutants and particulate matter, absorbing carbon dioxide and releasing oxygen through photosynthesis. This helps improve air quality, reduce pollution levels, and support respiratory health. Cleaner air reduces the environmental and health impacts of air pollution. This indirectly contributes to climate change mitigation by increasing public health and well-being (Sheweka et al., 2011).

Increasing levels of atmospheric carbon dioxide and GHGs lead to climate disruption. Green walls contribute to carbon sequestration by capturing carbon dioxide during photosynthesis and storing it in plant biomass and soil (Zaid et al., 2018). This helps offset carbon emissions and mitigate the greenhouse effect. Carbon sequestration by green walls contributes directly to climate change mitigation by reducing net carbon emissions and enhancing carbon storage in urban areas.

More intense rainfall events and stormwater runoff due to climate change, lead to flooding and water quality issues in urban areas. Green walls absorb and retain rainwater to a certain extent, reducing stormwater runoff and alleviating pressure on drainage systems (Bustami et al., 2018). They also filter pollutants from stormwater runoff, improving water quality. Improved stormwater management reduces flood risks, protects water resources, and enhances urban resilience to extreme weather events associated with climate change.

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Societal / socio-cultural benefits
  • Economic and social development
  • Energy security
  • Food security and quality
  • Human physical health and wellbeing
  • Waste management and sanitation

Green walls offer a range of societal and socio-cultural benefits, addressing various societal challenges and contributing to overall well-being.

Green walls create opportunities for green jobs in horticulture, landscaping, and maintenance. They enhance the aesthetic appeal of neighbourhoods, attract tourism, and contribute to property values and economic development addressing socio-economic disparities, unemployment, and limited access to green spaces and recreational areas in urban environments (Perini and Rosasco, 2013). Green walls support local economies, small businesses, and community pride. They promote social cohesion, civic engagement, and cultural identity by beautifying public spaces and fostering a sense of ownership and belonging.

Green walls may reduce energy demand for cooling in buildings, leading to energy savings and improved energy security (Pérez et al., 2014). They contribute to a more sustainable and resilient urban energy infrastructure. Green walls contribute to climate action, addressing concerns about energy affordability, reliability, and environmental impact. They are part of energy-efficient building practices and visually promote public awareness of sustainable living.

Green walls can include edible plants and herbs, promoting urban agriculture, food sovereignty, and local food production and addressing challenges such as limited access to fresh, healthy food and concerns about food security in urban communities (Tablada and Kosorić, 2022). They can contribute to food security, nutrition, and food system resilience. 

Green walls provide green spaces for recreation, relaxation, and exercise. They improve air quality, reduce noise pollution, and enhance psychological well-being. Green walls contribute to public health and well-being by creating healthier environments. They offer opportunities for outdoor activities, social interaction, and nature-based therapies, supporting holistic health and community resilience (Sheweka et al., 2011).

Urbanisation leads to increased waste generation, sanitation challenges, and environmental pollution. Green walls can be integrated with green infrastructure for waste management, such as composting or recycling systems. They contribute to cleaner air, water, and soil, improving overall environmental hygiene.

Climate-related stressors, such as heat waves, extreme weather, and environmental degradation, can impact mental health and well-being. Green walls promote biophilic design principles, connecting people with nature in built environments. They create visually appealing, calming spaces that reduce stress, enhance mood, and foster psychological resilience to climate-related challenges (Sheweka et al., 2011). Improved mental health and well-being contribute to community resilience and adaptive capacity in the face of climate change impacts. Living walls contribute to biophilic design principles by bringing nature into built environments, promoting well-being, and enhancing sustainability.

Green walls can serve as educational tools, supporting environmental literacy, plant science, and sustainable living. Education and knowledge dissemination through green walls raise public awareness about biodiversity conservation and ecosystem services. Green walls create opportunities for people to connect with nature in cities, fostering appreciation for biodiversity and environmental stewardship. They contribute to local ecosystem health and conservation efforts, promoting sustainable coexistence with urban wildlife.

Spiritual inspiration from green walls fosters a deeper meaningful connection to the natural world, promoting values of conservation, respect for life, and environmental stewardship (Manso and Castro-Gomes, 2015). They could be used to encourage cultural traditions, rituals, and practices that celebrate nature’s beauty and importance in human existence.

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Ecological and biodiversity benefits
  • Climate regulation
  • Fixation of solar energy
  • Food production (for humans)
  • Habitat provision
  • Medicinal resources
  • Species maintenance

Green walls support biodiversity by providing habitats for insects, birds, and plants in urban areas addressing loss of biodiversity and habitat fragmentation due to urbanisation and land use changes (Mayrand and Clergeau, 2018). They promote plant diversity, contribute to urban green spaces, and enhance ecological connectivity. Vertical greenery in walls offers nesting sites, shelter, and food sources for diverse species. Different plant species attract pollinators, birds, and beneficial insects, creating ecological niches and supporting urban biodiversity (Mayrand and Clergeau, 2018). 

Green walls support plant growth, reproduction, and survival, creating microhabitats for different species. They attract pollinators, birds, and beneficial insects, promoting ecological interactions and species diversity and therefore supporting ecosystem functioning, genetic diversity, and resilience to environmental changes (Mayrand and Clergeau, 2018). 

Solar energy fixation benefits plants by optimising photosynthesis and growth conditions. It also supports wildlife by creating cooler microhabitats and reducing thermal stress in urban landscapes.

Green walls can incorporate medicinal species known for their healing properties, such as herbs used in traditional medicine (Tablada and Kosorić, 2022). They also preserve traditional knowledge about medicinal plants and their cultural significance.

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Issues and Barriers

Several issues and barriers exist in relation to green walls that can impact the implementation, effectiveness, and widespread adoption of green walls.

Te Moananui Oceania experiences tropical cyclones, strong winds, heavy rainfall, and saltwater exposure in coastal areas. These environmental factors can affect the stability, maintenance, and longevity of green walls.

Green walls require robust structural support systems to hold the weight of plants, soil, and irrigation components. Ensuring structural integrity and safety is crucial, especially for tall or extensive green wall installations in urban environments.

Effective irrigation systems are essential for green wall health, but water distribution can be challenging, particularly in areas with limited access to freshwater or reliable water infrastructure (Bustami et al., 2018). Smart irrigation technologies, water recycling, and efficient water use practices are needed to address water management issues.

The availability of native plant species suitable for green walls may vary across Te Moananui Oceania, depending on local ecosystems, climate zones, and horticultural resources. Access to diverse plant species and knowledge about their suitability for vertical gardening is important for ecological integrity and biodiversity support.

Green walls require regular maintenance, including watering, pruning, possibly fertilising, pest control, and plant replacement. Adequate resources, skilled personnel, and sustainable maintenance practices are necessary to ensure the long-term viability and performance of green wall installations.

The upfront cost of designing, installing, and maintaining green walls can be significant, especially for large-scale or complex projects (Perini and Rosasco, 2013). Cost-effective solutions, innovative financing mechanisms, and incentives for green infrastructure development are needed to overcome financial barriers.

Finally, green wall installations may be subject to zoning regulations, building codes, and environmental permits, which could vary across jurisdictions in Te Moananui Oceania. Government policies, incentives, grants, and technical assistance can promote green infrastructure adoption and overcome financial barriers.

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Opportunities

Green walls offer opportunities to cool buildings, manage stormwater, and create green spaces. They also offer opportunities for carbon offsetting, green building certification, and climate-resilient infrastructure development, aligning with climate action goals and sustainability targets.

Green walls contribute to sustainable land use in Oceania by optimising vertical space, reducing land footprint, and promoting green infrastructure in urban areas. They offer opportunities for green building design, urban agriculture, and community gardens, supporting sustainable development goals and creating liveable, green cities. This may be a particular opportunity for nations where land is at a premium and is being impacted by sea level rise.

Green walls improve health and well-being by improving air quality, reducing stress, and enhancing urban environments. They offer opportunities for outdoor recreation, nature-based therapies, and mental health benefits, contributing to public health initiatives and quality of life improvements.

Green walls could enhance cultural identity, aesthetics, and artistic expressions by integrating Indigenous plants, cultural motifs, and traditional knowledge into green infrastructure projects. They offer opportunities for cultural tourism, educational programs, and community engagement, celebrating local heritage and promoting environmental stewardship.

Green walls create economic opportunities and green jobs by supporting horticulture, landscaping, maintenance services, and green technology industries (Pérez et al., 2014). They offer opportunities for innovation, entrepreneurship, and green economy development, contributing to economic resilience and sustainable growth.

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Financial case

The cost and benefits of green walls can vary widely depending on factors such as the size of the installation, complexity of the design, choice of plant species, irrigation systems, structural requirements, and maintenance needs. However, the return on investment of green walls depends on factors such as energy savings, property value appreciation, health benefits, and other environmental impact. Green walls can reduce energy consumption for cooling buildings by providing natural insulation, shading, and evapotranspiration. This can lead to lower electricity bills and energy cost savings (Pérez et al., 2014). Well-designed green walls can enhance property aesthetics, curb appeal, and market value. They may attract tenants, customers, and investors, leading to increased property demand and higher rental or resale prices (Perini and Rosasco, 2013). Green walls contribute to improved air quality, reduced stress, and enhanced mental health in indoor and outdoor spaces. These health benefits can result in productivity gains, reduced healthcare costs, and increased occupant satisfaction.

References
  • Akinwolemiwa, O. (2018). Developing affordable vertical greening systems and its impact on indoor comfort for low income groups in Lagos, Nigeria Cardiff University. 
  • Bustami, R. A., Belusko, M., Ward, J., & Beecham, S. (2018). Vertical greenery systems: A systematic review of research trends. Building and Environment, 146, 226-237.
  • Chen, C., Mao, L., Qiu, Y., Cui, J., & Wang, Y. (2020). Walls offer potential to improve urban biodiversity. Scientific Reports, 10(1), 9905.
  • Coma, J., Pérez, G., de Gracia, A., Burés, S., Urrestarazu, M., & Cabeza, L. F. (2017). Vertical greenery systems for energy savings in buildings: A comparative study between green walls and green facades. Building and Environment, 111, 228-237.
  • Cuce, E. (2017). Thermal regulation impact of green walls: An experimental and numerical investigation. Applied Energy, 194, 247-254.
  • Feng, H., & Hewage, K. (2014). Lifecycle assessment of living walls: air purification and energy performance. Journal of Cleaner Production, 69, 91-99.
  • Harmsworth, G.R., & Awatere, S. (2013). Indigenous Māori knowledge and perspectives of ecosystems. Ecosystem services in New Zealand—conditions and trends. Manaaki Whenua Press, Lincoln, New Zealand, 274-286.
  • Hikuroa, D. (2017). Mātauranga Māori—the ūkaipō of knowledge in New Zealand. Journal of the Royal Society of New Zealand, 47(1), 5-10. 
  • Kellert, S.R. (2003). Kinship to mastery: Biophilia in human evolution and development. Island Press.
  • Lee-Hammond, L. (2017). Belonging in nature: Spirituality, indigenous cultures and biophilia. The SAGE handbook of outdoor play and learning. London, UK: SAGE.
  • Manso, M., & Castro-Gomes, J. (2015). Green wall systems: A review of their characteristics. Renewable and sustainable energy reviews41, 863-871.
  • Mayrand, F., & Clergeau, P. (2018). Green roofs and green walls for biodiversity conservation: a contribution to urban connectivity? Sustainability10(4), 985.
  • Pérez, G., Coma, J., Martorell, I., & Cabeza, L. F. (2014). Vertical Greenery Systems (VGS) for energy saving in buildings: A review. Renewable and sustainable energy reviews39, 139-165.
  • Perini, K., & Rosasco, P. (2013). Cost–benefit analysis for green façades and living wall systems. Building and Environment70, 110-121.
  • Price, A., Jones, E. C., & Jefferson, F. (2015). Vertical greenery systems as a strategy in urban heat island mitigation. Water, Air, & Soil Pollution226, 1-11.
  • Sheweka, S., & Magdy, A. N. (2011). The living walls as an approach for a healthy urban environment. Energy Procedia6, 592-599.
  • Tablada, A., & Kosorić, V. (2022). Vertical farming on facades: transforming building skins for urban food security. In Rethinking Building Skins (pp. 285-311). Woodhead Publishing.Zaid, S. M., Perisamy, E., Hussein, H., Myeda, N. E., & Zainon, N. (2018). Vertical Greenery System in urban tropical climate and its carbon sequestration potential: A review. Ecological Indicators91, 57-70.