A green wall is a wall partially or completely covered with greenery that
includes a growing medium, such as soil. Most green walls also feature an
integrated water delivery system. Green walls are also known as living walls or
vertical gardens. It is useful to distinguish green walls
from green facades. Green walls have growing media supported on the face of
the wall, while green facades have soil only at the base of the wall and support
climbing plants on the face of the wall to create the green, or vegetated,
facade. Green walls may be indoors or outside,
freestanding or attached to an existing wall, and come in a great variety of
sizes. As of 2015, the largest green wall covers 2,700 square meters and is
located at the Los Cabos International Convention Center, a building designed
by Mexican architect Fernando Romero for the 2012 G-20 Los Cabos summit.
Green walls have seen a recent surge in popularity. Of the 61 large-scale
outdoor green walls listed in an online database provided by greenroof.com, 80%
were constructed in or after 2009 and 93% dated from no later than 2007. Many
Iconic green walls have been constructed by Institutions and in public places
such as Airports and are now becoming common, to improve the aesthetics. For
example: Edmonton International Airport, Singapore Changi Airport & Chhatrapati
Shivaji International Airport. While Patrick Blanc is sometimes
credited as having developed the concept in the late 1980s, the actual inventor
is Stanley Hart White, a Professor of Landscape Architecture who patented a
green wall system in 1938. Types
Green walls are often constructed of modular panels that hold a growing
medium and can be categorized according to the type of growth media used: 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 are then 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. 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. There are some systems in Asia that have
solved the loose media erosion problem by use of shielding systems to hold the
media within the green wall system even when soil liquefaction occurs under
seismic load. In these systems, the plants can still up-root themselves in
the liquified soil under seismic load, and therefore it is required that the
plants be secured to the system to prevent them from falling from the wall.
Loose-soil systems without physical media erosion systems are best suited
for the home gardener where occasional replanting is desired from season to
season or year to year. Loose-soil systems with physical media erosion
systems are well suited for all green wall applications.
= Mat Media = Mat type systems tend to be either coir
fiber 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 by cutting the mat out of the
wall and replacing it with new mat. This process compromises the root structures
of the neighboring plants on the wall and often kills many surrounding plants
in the reparation process. These systems are best used on the interior of a
building and are a good choice in areas with low seismic activity and small
plants that will not grow to a weight that could rip the mat apart under their
own weight over time. 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 often 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. = Sheet Media =
Semi-open cell polyurethane sheet media utilising an egg crate pattern has
successfully been used in recent years for both outdoor roof gardens and
vertical walls. The water holding capacity of these engineered
polyurethanes vastly exceeds that of coir and felt based systems.
Polyurethanes do not biodegrade, and hence stay viable as an active substrate
for 20+ years. Vertical wall systems utilising polyurethane sheeting
typically employ a sandwich construction where a water proof membrane is applied
to the back, the polyurethane sheeting is laid and then a mesh or anchor
braces/bars secure the assembly to the wall. Pockets are cut into the face of
the first urethane sheet into which plants are inserted. Soil is typically
removed from the roots of any plants prior to insertion into the urethane
mattress substrate. A flaked or chopped noodle version of the same polyurethane
material can also be added to existing structural media mixes to boost water
retention. = Structural Media =
Structural media are growth medium "blocks" that are not loose, nor mats,
but which 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 replacement.
There is also some discussion involving "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 building's HVAC system to be
recirculated throughout the building. A problem with these systems is that
building code still requires 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. Early studies in this area include NASA
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."The Effect of Indoor Foliage Plants on Health and Discomfort Symptoms
among Office Workers". Retrieved 2010-12-23. .
Function Green walls are found most often in
urban environments where the plants reduce overall temperatures of the
building. "The primary cause of heat build-up in cities is insolation, 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 by absorbing the dissolved nutrients. Bacteria mineralize
the organic components to make them available to the plants. A study is
underway at the Bertschi School in Seattle, Washington using a GSky Pro
Wall system, however, no publicly available data on this is available at
this time. 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 gardening, or
for its beauty as art. It is sometimes built indoors to help alleviate sick
building syndrome. See also
Building-integrated agriculture Folkewall
Green roof Greenwall
The Hanging Gardens of Babylon Humulus lupulus
Musée du Quai Branly The Green Wall, a film
The Green Wall: The Story Of A Brave Prison Guard's Fight Against Corruption
Inside The United States' Largest Prison System, a book D.J. Vodicka about
corruption in the California prison system
Vertical farming References
External links Green Infrastructure Resource Guide
Green wall tower IPH in Hanoi, VietNam