ABOUT GREEN WALLS
Overview of Green Walls
The term green walls encompasses all forms of vegetated wall surfaces. However, there are three major system categories that fall under this term: green facades, living walls, and retaining living walls.
Categorization of Systems
Green Facades
Green facades utilize vines and climbing plants that grow on structures specifically designed for them. These plants are rooted in various locations, from ground soil to rooftops, and mature over several seasons.
Key Features:
Attachment: Can be affixed to existing walls or constructed as independent entities.
Applications: Ideal for shading, creating green walkways, and architectural enhancements.
Environmental Adaptability: Flourishes in diverse climates and orientations.
Living Walls (e.g., Biowalls, 'Mur' Vegetal)
These walls comprise pre-vegetated panels or modules that support a wide variety of plant species. Living walls can be found in both indoor and outdoor settings, thriving in full sun or shade.
Key Features:
Diversity: Supports a richer array of plants compared to green facades.
Structural Variety: Made from materials like plastic, fabric, and concrete.
Versatile Applications: Suitable for tropical and temperate locations.
Retaining Living Walls
Engineered to stabilize slopes, retaining living walls combine structural strength with the capacity for lush vegetation. These modular systems can adapt to various angles and are effective in erosion control.
Key Features:
Engineering Excellence: Designed to withstand lateral soil forces.
Modular Design: Facilitates ease of installation.
Eco-Friendly: Transforms into vibrant green spaces over time.
They are often modular for ease of installation, and made of geo-textile bags in conjunction with interlocking units, metal, concrete, plastic cellular confinement mats or woven willow plants. Some systems can perform on slopes up to 88 degrees and many have the capacity for variable slope angles as flat as 45 degrees. While performing the same structural function as their more widely known non-living, solid-faced predecessors, all living retaining wall systems and methods must allow for a suitable volume of soil at the face of the system. The growing media must be sheltered from erosion, be accessible to the introduction of plant material either from plugs or seed and provide for long-term plant growth. The mature living retaining wall is intended to be fully covered by its internally supported vegetation such that the underlying structural elements are no longer visible as the wall becomes additional green space and habitat for the project.
Green Wall Benefits
Green walls are transforming urban landscapes, offering a myriad of benefits that extend beyond their immediate aesthetic appeal. From enhancing public spaces to improving personal well-being and contributing to environmental sustainability, the impact of green walls is profound and multifaceted. It's important to note, however, that each green wall installation is unique, with variations in benefits depending on the region, climate, building design, and type of green wall. For expert guidance and more detailed information, GRHC members are invaluable resources, and a comprehensive resource manual is available from GRHC's Green Infrastructure Store.
Public Benefits
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• Green walls can reclaim disregarded space by providing aesthetic stimulation where it would not otherwise be found.
• They can also serve to create privacy and a sense of enclosure while limiting the negative psychological effects associated with property demarcation.
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• The reintroduction of vegetation into urban environments promotes the occurrence of natural cooling processes, such as photosynthesis and evapotranspiration.
• With strategic placement of green walls, plants can create enough turbulence to break vertical airflow, which slows and cools down the air (Peck et al. 1999).
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• Green walls mitigate air pollution levels by lowering extreme summer temperatures through photosynthesis, trapping particulate matter, and capturing gases.
• The ability of green walls to provide thermal insulation for buildings means less demand on power, and as a result, fewer polluting by-products are released into the air.
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•Green walls draw upon several disciplines for their design, installation, and maintenance
•Demand for a local supply of plant materials, blended growing media, greenhouse production, and fabrication of structural frames creates further business activity.
Private Benefits
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• Green walls can reduce the temperature fluctuations at a wall's surface from a range of 10-60°C (50-140°F) to one of 5-30°C (41-86°F), in turn, limiting the movement of heat between building walls (Minke 1982). They cause this reduction by:
○ Trapping a layer of air within the plant mass.
○ Reducing ambient temperature via evapotranspiration and shading.
○ Creating a buffer against wind during winter months.
• Green walls can help lower the air temperature around intake valves, which means HVAC units will require less energy to cool air before being circulated around a building.
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• Temperature fluctuations over a building's lifetime can be damaging to organic construction materials in building facades. Green walls provide an additional layer of exterior insulation and thereby limit thermal fluctuations.
• Green walls protect exterior finishes and masonry from UV radiation and rain. They can also increase the seal or air tightness of doors, windows, and cladding by decreasing the effect of wind pressure (Peck et al. 1999).
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• Most North Americans spend 80-90% of their time indoors (Jenkins et al. 1992) and as a result, are highly influenced by the effectiveness of interior air circulation systems. It has been estimated that problems associated with poor indoor air quality negatively affect workplace production by $60 billion per year in the United States (Reitze 1998).
• Air that has been circulated throughout a building with a strategically placed green wall (such as near an air intake valve) will be cleaner than that on an uncovered building. The presence of vegetation indoors will have the same effect.
• These processes remove airborne pollutants such as toluene, ethyl benzene, xylene, and other volatile organic compounds.
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• The vegetated surface provided by strategic urban greenery such as green walls and roofs will block high-frequency sounds, and when constructed with a substrate or growing medium support can also block low-frequency noises.
• For over 30 years, plant life has been used to this end along freeways, arterials, and rail lines in North America and Europe.
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• Green buildings, products, and services now possess a competitive edge in the marketplace.
• Green walls are an easily identifiable symbol of the green building movement since they are clearly visible and directly impact the amount of green space in urban centers.
Design Specific Benefits
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• Green walls can help mitigate the loss of biodiversity due to the effects of urbanization, help sustain a variety of plants, pollinators and invertebrates, and provide habitat and nesting places for various bird species.
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• Buildings that feature and promote access to vegetation have been documented as having a greater positive human health impact than those without (Honeyman 1987)
• Studies have shown that visual access to natural settings lead to increased job satifaction and productivity (Kaplan 2001) and post-operative recovery rates in medical facilities (Ulrich 1983).
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• Green walls offer the opportunity for urban agriculture, such as vertical gardens of small fruits, vegetables, and herbs.
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• Several water-recycling systems can be applied to green walls. These systems pump grey water through a green wall, which then passes through filters, gravel, and marine plants.
• Treated water is then sent to a grey water holding tank for household or irrigation use or released into the public water treatment system (Shirley-Smith 2006). Some of these systems also collect stormwater, which is filtered for household use or irrigation purposes..