All your questions answered by the living wall gurus
How is a living wall / green wall constructed? What are the benefits of a living wall / green wall? What is the difference between a living wall, green wall, green façade or a vertical garden? What plants are used in living walls or green walls? All your questions answered by the living wall gurus: Pritchard & Pritchard. If you have any other questions please email us.
What is a living wall or green wall?
Living walls are indoor or outdoor walls or fences that are partially or wholly covered in vegetation. There are three ways of achieving this:
1) Traditionally living walls were created by vigorous climbing plants, trees or shrubs, planted at the base of the wall, fence or structure and trained or encouraged to grow up a trellis attached to the wall. This is centuries, if not millennia old. This is often referred to as a green façade to distinguish it from its modern cousin the (modular) green wall. See: Green façades
2) The hanging garden is another traditional method for greening a wall, where trailing plants are planted in pots at the top of a wall and dangle down the wall. This method could date back to ancient times.
3) The modular green wall has become increasingly popular from the turn of the century. This system uses a framework of troughs, pockets or mats affixed to a wall or fence into which a multitude of smaller plants are planted. See: Modular green wall
How is a living wall / green wall constructed? What is a living wall system?
Modular green walls, a.k.a. green walls, vertical gardens, vertical planting requires:
1. A steel framework is affixed to a wall, fence or other structure;
2. Depending on system, to this is attached a) a network of troughs or pockets in which plants are planted in growing medium or b) pre-vegetated mats.
3. The plants are positioned on the wall according to the planting plan, which takes into account, visual impact, coverage, year round interest, bio-diversity etc.
4. The plants are fed and watered using an irrigation system or hydroponics system.
5. All walls require a maintenance system to ensure that plants remain healthy and are replaced when required.
How is a green façade / climber wall constructed? What is a living wall system?
A green façade / climber wall requires:
1. A metal trellis is constructed using a stainless steel wire rope and bar system. This could be attached to the wall or fence, or set off from the wall or free standing.
2. Vigorous climbing plants, trees or shrubs are planted at the base of the wall, fence or other structure, in a bed or planters.
3. The climbing plants, trees or shrubs are trained to the trellis and trained as they grow up the trellis.
What are the guidelines for creating living walls? How do you choose a living wall system, supplier and installer?
There is no UK living walls equivalent of the German FLL Guidelines for the Planning, Construction and Maintenance of Green Roofs or the Gro Green Roof Code which makes it very important to choose a green wall system, manufacturer and installer with proven longevity and expertise.
What are the types of living wall? What is the difference between a living wall, green wall, green façade or a vertical garden?
There are three categories of living wall: 1. Modular green wall vertical garden vertical planting; 2. Green façades or climber wall; 3 Hanging garden or hanging wall.
1. Modular green walls, a.k.a. green walls, vertical gardens, vertical planting
A multitude of small plants are grown all over a vertical structure in the place they are required, without needing to be rooted into the ground, mimicking the way plants grow in cliffs and old walls. Systems vary, but require a steel framework to be affixed to a wall, fence or other structure, onto which a network of troughs, pockets or modules into which the plants are planted. Planting different species in according to a planting plan can create an attractive pattern or even an image, as well as improving diversity and round the year interest. The plants need regularly watering and feeding with nutrients through an irrigation system. Mat systems will use a soil-less hydroponics system to grow the plants. Green walls have become increasingly popular from the turn of the century for both indoor and outdoor installations, though the first modern green wall harks back to 1986. See: Modular green wall
2. Green façades, a.k.a. climber walls, climbing façades or vertical gardens
Vigorous climbing plants, trees or shrubs, are planted at the base of the wall, fence or other structure, in a bed or planters and trained to grow up a trellis. This also could be interior or exterior. The green façade method is centuries, if not millennia old, and there are lots of examples of very old climbing plants – for example the 200 year old wisteria covering the wall at Fullers’ Griffin Brewery. Traditionally the trellis would be made of wood, but since the 1990s installations have tended to use innovative stainless steel wire rope and bar systems. A stainless steel trellis can be close to the wall or stepped away, or can be used as part of a freestanding fence/structure. See: Green façades
3. Hanging garden or hanging wall
Trailing plants are planted in planters at the top of a wall or affixed to a wall (e.g. window box or balcony), and allowed to dangle down the wall. Arguably this method is as old as the hanging gardens of Babylon.
Who invented the living wall or green wall?
Green façades and hanging gardens have been around for centuries, arguably millennia.
The modern modular green wall, where plants are grown in a vertical structure was invented by US inventor Professor Stanley Hart White, who patented the “Vegetation-Bearing Architectonic Structure and System” in 1938, but little happened commercially for 50 years.
In the 1980s French botanist Patrick Blanc ‘reinvented’ the green wall. Blanc pioneered a soil-less system that grow vegetation into mats hung vertically attached to a steel structure fed by hydroponic irrigation system.
Blanc’s first green wall was inside the Cité des Sciences et de l’Industrie in Paris in 1986, but the idea didn’t gain much traction until the late 1990s.
What plants are used in living walls, green walls, green façades and hanging walls?
Modular green walls
- Famously the wall at Quai Branly Museum in Paris includes 150 different species of plant (15,000 plants in total), which is a trifle excessive.
- Most living walls use a fraction of that number of species.
- Outdoor modular walls use a mix of compact hardy, drought-tolerant herbaceous perennials, shrubs and grasses, with the majority being evergreen. Combinations include sun lovers for sunny spots, shade tolerant plants for shadier spots, such as ferns, Hellebore and Heuchera. Edible plants such as herbs, strawberries and tomatoes can also be used.
- Indoor modular walls use a mix of tropical plants that can cope with reduced or artificial light and air conditioning.
Green façade planting includes:
- Vigorous climbing plants, often evergreen varieties, including Wisteria, grape vines, Trachelospermum, clematis, honey suckle, Virginia creeper.
- Trained fruit, such as figs, ornamental trees, such as Magnolia, or shrubs, such as Garrya or roses.
Hanging walls, planting includes:
- Climbing plants, often evergreen varieties, including ivy, Trachelospermum, Virginia creeper.
What are the benefits of a living or green wall?
A living wall can deliver the following benefits, according to Living Roofs and Walls Technical Report: Supporting London Plan Policy (2008):
- By providing shading from the sun, living walls can significantly reduce the external temperature of a building. Depending on plant coverage, temperature fluctuations at the wall surface can be reduced from between 10°C and 60°C to between 5°C and 30°C.
- Living Walls provide winter insulation. Creating a zone of still air adjacent to the wall, evergreen plants can reduce convection at the wall surface by up to 75 per cent and heating demand by up to 25 per cent.
- Living Walls can reduce wall wetting thus reducing the amount of cooling through evaporation at the wall’s surface (and thus energy loss).
- The interception of both light and heat radiation by living walls helps reduce Urban Heat Island effect (UHIE).
- Climbers on buildings protect the surface of the building from damage, particularly from very heavy driving rainfall and hail.
- They help to shield wall surfaces from ultra-violet light which could damage building materials.
- They help trap dust and other pollutants from both the air and rainfall on the leaves of plants.
- Living Walls improve biodiversity by:
- Providing a food source for invertebrates (which are eaten by birds).
- Providing breeding and nesting habitat for invertebrates, birds (including the house sparrow), and possibly bats.
In addition BREEAM (Building Research Establishment Environmental Assessment Method) points out that living walls can deliver the following benefits:
1) They benefit people and community, by improving health, wellbeing and comfort, as well as heritage and local character, by:
- Being more aesthetically pleasing than many conventional walling solutions, reducing the visual impact of development.
- Providing opportunities for growing food and education.
2) They reduce construction and operational impacts, by:
- Reducing surface water runoff.
- Improving noise inside and out by the sound absorption capabilities of plants.
- Improving air quality.
- Help reducing light pollution, by shielding street lights and internal lights and removing reflective walls.
3) They help mitigate climate change, by:
- Reducing a building’s surface temperatures through shading and evaporative cooling so providing significant reduction in the Urban Heat Island effect.
- Absorbing the heat above street level, preventing pavements and associated social spaces from heating up and can offer an evaporative cooling effect for users of these spaces.
How do living walls reduce energy costs of a building?
According to BREEAM (Building Research Establishment Environmental Assessment Method):
- Green walls “can help to reduce demands for artificial heating and cooling by contributing to insulation performance and reducing demands through solar gain and wind generated heat loss. This both helps to reduce energy demand and its associated costs as well as conveying resilience to future climate change in a visible manner, thus assisting in demonstrating corporate social responsibility”.
Living Roofs and Walls Technical Report: Supporting London Plan Policy (2008) cites the following research:
- By providing shading from the sun, living walls can reduce temperature fluctuations at the wall surface from between 10°C and 60°C to between 5°C and 30°C.
- By creating a zone of still air adjacent to the wall, evergreen plants can reduce convection at the wall surface by up to 75 per cent and heating demand by up to 25 per cent.
- Living Walls can reduce wall wetting. Wetting causes cooling through evaporation at the wall’s surface (and thus energy loss).
How do living walls, green walls and green façades impact biodiversity?
German FLL Guidelines states that walls with a high degree of structural diversity, e.g. intensive, extensive green with raised areas and woody vegetation have the ‘highest faunistic diversity’. It is also recommended that walls should be connected to the surrounding landscape by greening façades.
A living wall can deliver the following benefits, according to Living Roofs and Walls Technical Report: Supporting London Plan Policy (2008) Living Walls improve biodiversity by:
- Providing a food source for invertebrates (which are eaten by birds).
Do living walls or green walls impact chances of getting planning permission?
The construction and planning guidelines of many countries and cities explicitly require provision for green walls, roofs, roof terraces and sustainable drainage systems SuDS. Some places have gone further, introducing incentives and enshrining urban greening into law.
The direction of travel in the UK is clear from the guidance for developers and planners in London.
Sustainable Design and Construction SPG provisions (2014) for London states: APPENDIX 4, 6.4.3.
- “The [London] Mayor has a target to increase the green cover in the CAZ (Clean Air Zone) by 5% on 2008 levels by 2030 (an increase of approximately 30ha). To facilitate the delivery of this target, developments should maximise the provision of green infrastructure within their developments. The green infrastructure most applicable in the most densely developed part of the city are urban greening measures such as green roofs, green walls, rain gardens and street trees.”
- Boroughs should encourage local food growing by safeguarding south facing spaces, planting walls with espaliers or climbing plants; integrating edible plants with ornamental plants and proving planters that can be easily converted for food growing.
- To conserve energy, developers should incorporate green walls that can keep buildings and the surroundings warm or cool; and improve biodiversity.
- Developers of schemes which do not meet the ‘air quality neutral’ benchmark… will be required to off-set any excess in emissions… including: green planting/walls and screens, with special consideration given to planting that absorbs or supress pollutants.
Living Walls and Walls Technical Report: Supporting London Plan Policy (2008) recommended the following policy statement:
“The Mayor will and boroughs should expect major developments to incorporate living walls and walls where feasible and reflect this principle in LDF policies. It is expected that this will include roof and wall planting that delivers as many of these objectives as possible:
- Accessible space
- Adapting to and mitigating climate change
- Sustainable urban drainage
- Enhancing biodiversity
- Improved appearance.
BREEAM states that green walls can only be included for credits in the ‘Enhancing site ecology’ assessment only where there is evidence that a comprehensive on-going maintenance strategy will be in place.
How much maintenance does a living wall or green wall require?
All green walls require some degree of maintenance because they are living systems.
- Modular green walls require more maintenance due to the complexity of the system and the number of plants. Mat based systems require regular replacements of the mat panels.
- Green façades which contain more vigorous plants, require more training to keep plants away from windows, gutters etc.
Maintenance regimes for living walls require the following tasks:
- Inspection and functional testing of irrigation systems
- Inspecting cable and wire-rope systems
- Feeding and fertilizing
- Removing weeds
- Cutting back climbers and perennials
- Pruning woody plants
- Repeat seeding
- Repeat planting
- Pest control
- Removal of refuse
- Plant protection
- Inspection of the drainage system
BREEAM states that green walls can only be included in the ‘Enhancing site ecology’ assessment where there is evidence that a comprehensive on-going maintenance strategy will be in place.
How long does a living wall / green wall last?
A properly installed, irrigated and maintained living wall should last for many years.
- There are plenty of green façades that have lasted hundreds of years, such the 200 year old wisteria covering the wall at Fullers’ Griffin Brewery.
- Modular green façades are a newer innovation so there are not many long-lived examples. The oldest modular green wall is at Cité des Sciences et de l’Industrie in Paris, created in 1986 and still going strong.
How much does a living wall cost?
Every living wall installation is bespoke. The cost calculation takes into account the following factors:
- Wall size
- Wall height
- Type of living wall
- Planting scheme
- Location and access
- Indoor or outdoor
- Condition of the wall
- Maintenance package