Living wall - AbsoluteAstronomy.com

A green wall is a wall, either free-standing or part of a building, that is partially or completely covered with vegetation and, in some cases, soil or an inorganic growing medium. The concept of the green wall dates back to 600 BC with the Hanging Gardens of Babylon.

Hanging Gardens of Babylon

The Hanging Gardens of Babylon were considered to be one of the greatest Seven Wonders of the Ancient World, and the only one of the Wonders which may in fact have been legendary. They were purportedly built in the ancient city-state of Babylon, near present-day Al Hillah, Babil, in Iraq...

More recently, the larger green walls concept has been utilized with innovative hydroponics

Hydroponics

Hydroponics is a method of growing plants using mineral nutrient solutions, in water, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel, mineral wool, or coconut husk.Researchers discovered in the 18th...

technology by the French botanist Patrick Blanc

Patrick Blanc

Patrick Blanc is a botanist, working at the French National Centre for Scientific Research, where he specializes in plants from tropical forests...

. The vegetation for a green façade is always attached on outside walls; with living walls this is also usually the case, although some living walls can also be green walls for interior use. For living walls there are many methods including attaching to the air return of the building to help with air filtration. They are also referred to as living walls

Living wall

A green wall is a wall, either free-standing or part of a building, that is partially or completely covered with vegetation and, in some cases, soil or an inorganic growing medium. The concept of the green wall dates back to 600 BC with the Hanging Gardens of Babylon...

, biowalls, vertical gardens or more scientifically VCW_V (Vertical Vegetated Complex Walls).

Types

There are two main categories of green walls: green façades and living walls. Green façades are made up of climbing plants either growing directly on a wall or, more recently, specially designed supporting structure

Structure

Structure is a fundamental, tangible or intangible notion referring to the recognition, observation, nature, and permanence of patterns and relationships of entities. This notion may itself be an object, such as a built structure, or an attribute, such as the structure of society...

s. The plant shoot system grows up the side of the building while being rooted in the ground. With a living wall the modular panels are often made of stainless steel containers, geotextile

Geotextile

Geotextiles are permeable fabrics which, when used in association with soil, have the ability to separate, filter, reinforce, protect, or drain...

s, irrigation

Irrigation

Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...

systems, a growing medium and vegetation.

There are three types of growth media used in living walls, loose media, mat media and structural media.

Loose media

Loose medium walls tend to be "soil-on-a-shelf" or "soil-in-a-bag" type systems. Loose medium systems have their soil packed into a shelf or bag and then are installed onto the wall. These systems require their media to be replaced at least once a year on exteriors and approximately every two years on interiors. Loose soil systems are not well suited for areas with any seismic activity. Reparations are only achieved by re-stuffing soil into the holes on the wall, which is both difficult and messy. Loose-soil systems should not be used in areas where there will be a lot of public interaction as they are quite messy and lose their soil little by little over time as their medium wets and dries, falling out onto the floor in front if not properly designed. Most importantly, because these systems can easily have their medium blown away by wind-driven rain or heavy winds, these should not be used in applications over 8 feet high. Loose-soil systems are best suited for the home gardener where occasional replanting is desired from season to season or year to year.

Mat media

Mat type systems tend to be either coir fibre or felt mats. Mat media are quite thin, even in multiple layers, and as such cannot support vibrant root systems of mature plants for more than three to five years before the roots overtake the mat and water is not able to adequately wick through the mats. The method of reparation of these systems is to replace large sections of the system at a time which compromises the root structures of the neighboring plants on the wall. These systems are best used on the interior of a building and are a good choice in areas with seismic activity. It is important to note that mat systems are particularly water inefficient and often require constant irrigation due to the thin nature of the medium and its inability to hold water and provide a buffer for the plant roots. This inefficiency requires that these systems have a water re-circulation system put into place at an additional cost. Mat media are better suited for small installations no more than eight feet in height where repairs are easily completed.

Structural media

Structural media are growth medium "blocks" that are not loose, nor mats, but incorporate the best features of both into a block that can be manufactured into various sizes, shapes and thicknesses. These media have the advantage that they do not break down for 10 to 15 years, can be made to have a higher or lower water holding capacity depending on the plant selection for the wall, can have their pH and EC's customized to suit the plants, and are easily handled for maintenance and replacements. They are the most robust option for a living wall for both exterior applications and for interior applications. They are the only choice in areas where high-winds, seismic activity or heights need to be addressed in the design. Structural media are superior to the other media for their longevity and high-level of performance in a variety of circumstances. Depending on the installation, they do tend to be more expensive to install, but lower cost to maintain.

There is some discussion also around "active" living walls. An active living wall actively pulls or forces air through the plants leaves, roots and growth medium of the wall and then into the buildings HVAC system to be recirculated throughout the building. A problem with these systems is that building code still requires that all the standard air filtration equipment that would have to be installed anyway, despite the living wall's installation. This means that active living walls do not improve air quality to the point that the installation of other air quality filtration systems can be removed to provide a cost-savings. Therefore, the added cost of design, planning and implementation of an active living wall is still in question. With further research and UL standards to support the air quality data from the living wall, building code may one day allow for our buildings to have their air filtered by plants.

The area of air quality and plants is continuing to be researched. The majority of the research cited is from NASA's studies performed in the 1970s and 1980s by B.C. Wolverton. There was also a study performed at the University of Guelph by Alan Darlington. Other research has shown the effect the plants have on the health of office workers..

Function

Green walls are found most often in urban environments

Urban area

An urban area is characterized by higher population density and vast human features in comparison to areas surrounding it. Urban areas may be cities, towns or conurbations, but the term is not commonly extended to rural settlements such as villages and hamlets.Urban areas are created and further...

where the plants reduce overall temperatures of the building. "The primary cause of heat build-up in cities is insolation

Insolation

Insolation is a measure of solar radiation energy received on a given surface area in a given time. It is commonly expressed as average irradiance in watts per square meter or kilowatt-hours per square meter per day...

, the absorption of solar radiation by roads and buildings in the city and the storage of this heat in the building material and its subsequent re-radiation. Plant surfaces however, as a result of transpiration, do not rise more than 4–5 °C above the ambient and are sometimes cooler."

Living walls may also be a means for water reuse. The plants may purify slightly polluted water (such as greywater

Greywater

Greywater is wastewater generated from domestic activities such as laundry, dishwashing, and bathing, which can be recycled on-site for uses such as landscape irrigation and constructed wetlands...

) by absorbing the dissolved nutrients. Bacteria mineralize the organic components to make them available to the plants.

Living walls are particularly suitable for cities, as they allow good use of available vertical surface areas. They are also suitable in arid areas, as the circulating water on a vertical wall is less likely to evaporate than in horizontal gardens.

The living wall could also function for urban agriculture

Urban agriculture

Urban agriculture is the practice of cultivating, processing and distributing food in, or around, a village, town or city. Urban agriculture in addition can also involve animal husbandry, aquaculture, agro-forestry and horticulture...

, urban gardening

Urban gardening

Urban gardening may refer to:* Container garden - Growing plants in pots or other containers, rather than in ground* Urban horticulture - Growing crops or ornamental plants in urban or semi-urban setting* Urban agriculture - Food production in urban setting...

, or for its beauty as art

Art

Art is the product or process of deliberately arranging items in a way that influences and affects one or more of the senses, emotions, and intellect....

. It is sometimes built indoors to help alleviate sick building syndrome

Sick building syndrome

Sick building syndrome is a combination of ailments associated with an individual's place of work or residence. A 1984 World Health Organization report into the syndrome suggested up to 30% of new and remodeled buildings worldwide may be linked to symptoms of SBS...

Green façades

Some popular plants (for temperate climates) include:

Actinidia
Actinidia
Actinidia is a genus of woody and, with few exceptions, dioecious plants native to temperate eastern Asia, occurring throughout most of China, Taiwan, Korea and Japan, and extending north to southeast Siberia and south into Indochina...
Akebia quinata/trifoliata
Aristolochia
Aristolochia
Aristolochia is a large plant genus with over 500 species. Collectively known as birthworts, pipevines or Dutchman's pipes, they are the namesake of the family . They are widespread and occur in the most diverse climates. Some species, like A. utriformis and A...
Campsis
Campsis
Campsis is a genus of flowering plants in the bignonia family, Bignoniaceae. It consists of two species, both of which are vines with large flowers.-Species:* Campsis grandiflora K.Schum. – Chinese Trumpet Vine...
Celastrus
Clematis
Clematis
Clematis is a genus of about 300 species within the buttercup family Ranunculaceae. Their garden hybrids have been popular among gardeners beginning with Clematis × jackmanii, a garden standby since 1862; more hybrid cultivars are being produced constantly. They are mainly of Chinese and Japanese...
Cotoneaster
Cotoneaster
Cotoneaster is a genus of woody plants in the rose family, Rosaceae, native to the Palaearctic region , with a strong concentration of diversity in the genus in the mountains of southwestern China and the Himalayas...
Euonymus fortunei
Euonymus fortunei
Euonymus fortunei, also commonly known as winter creeper or wintercreeper and Fortune's spindle is a species of Euonymus native to east Asia, including China, Korea, Philippines and Japan....
Hedera
Heuchera
Heuchera
The genus Heuchera includes at least 50 species of herbaceous perennial plants in the family Saxifragaceae, all native to North America. Common names include alumroot and coral bells. They have palmately lobed leaves on long petioles, and a thick, woody rootstock...
Humulus lupulus
Humulus lupulus
Humulus lupulus is a species of Humulus in the Cannabaceae family.Common hop is a dioecious, perennial herbaceous climbing plant which sends up new shoots in early spring and dies back to the cold-hardy rhizome in autumn...
Hydrangea petiolaris
Hydrangea petiolaris
Hydrangea petiolaris, a Climbing hydrangea , is a species of Hydrangea native to the woodlands of Japan, the Korean peninsula, and on Sakhalin island of easternmost Siberia in the Russian Far East...
Lonicera
Nephrolepis
Nephrolepis
Nephrolepis is a genus of about 30 species of ferns in the family Nephrolepidaceae or Lomariopsidaceae .-Selected species:* Nephrolepis biserrata Schott. Nephrolepis is a genus of about 30 species of ferns in the family Nephrolepidaceae or Lomariopsidaceae (included in Davalliaceae in some...
Parthenocissus tricuspidata
Parthenocissus tricuspidata
Parthenocissus tricuspidata is a flowering plant in the grape family native to eastern Asia in Japan, Korea, and northern and eastern China...

/quinquefolia
Parthenocissus quinquefolia
Virginia creeper, five-leaved ivy, or five-finger is a woody vine native to eastern and central North America, in southeastern Canada, the eastern and central United States, eastern Mexico, and Guatemala, west as far as Manitoba, South Dakota, Utah and Texas.-Growth:It is a prolific climber,...

/inserta
Vitis berlandieri / riparia
Polygonum auberti
Pyracantha
Pyracantha
Pyracantha is a genus of thorny evergreen large shrubs in the family Rosaceae, with common names Firethorn or Pyracantha. They are native to an area extending from Southeast Europe east to Southeast Asia, resemble and are related to Cotoneaster, but have serrated leaf margins and numerous thorns...
Selaginella
Wisteria
Wisteria
Wisteria is a genus of flowering plants in the pea family, Fabaceae, that includes ten species of woody climbing vines native to the eastern United States and to China, Korea, and Japan. Aquarists refer to the species Hygrophila difformis, in the family Acanthaceae, as Water Wisteria...

External links

Largest Vertical Garden in North America - Semiahmoo Green Wall by Green over Grey
Vertical and verdant, living wall systems sprout on two buildings, in Paris and Vancouver, Architectural Record
Living wall at University of Guelph-Humber wins RAIC award
Green Infrastructure Resource Guide
Vertical Gardens of Patrick Blanc. Lecture delivered at the California Academy of Sciences. 2009
Biowall, Drexel University. Philadelphia

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