Vol.1, No.1, 1-8 (2011)
Open Journal of Ecology
opyright © 2011 SciRes. OPEN ACCESS
Greening the building envelope, façade greening and
living wall systems
Katia Perini1, Marc Ottelé2, E. M. Haas2, Rossana Raiteri1
1Faculty of Architecture, University of Genoa Stradone S. Agostino, 37 - 16123 Genoa, Italy; katiaperini@hotmail.com
2Faculty of Civil Engineering and Geosciences, Delft University of Technology Stevinweg 1, 2628 CN Delft, P.O. Box 5048, The
Netherlands; M.Ottele@tudelft.nl
Received 5 May, 2011; revised 12 May, 2011; accepted 21 May, 2011.
For greening the building envelope several
concepts can be used, for example green roofs,
façades greened with climbing plants or living
wall systems (modular pre-vegetated panels),
etc. Greening the building envelope allows to
obtain a relevant improvement of the its effi-
ciency, ecological and environmental benefits
as well as an increase of the biodiversity. Since
the interest restoring the environmental integ-
rity of urban areas continues to increase, new
developments in construction practices with
beneficial environmental characteristics take
place, as vertical greening systems. Applying
green façades is not a new concept and can
offer multiple benefits as a component of cur-
rent urban design; considering the relation be-
tween the environmental benefits, energy sav-
ing for the building and the vertical greening
systems (material used, maintenance, nutrients
and water needed) the integration of vegetation
could be a sustainable approach for the enve-
lope of new and existing buildings.
Keyw ords: Façade Greening; Living Wa ll Systems;
Nature In Cities; Environmental Benefits;
Environmental Impact; Sustainability
The ecological theories, from 1866 up until today,
have contributed to the diffusion of a better awareness as
far as our actions on a global level are concerned. The
attention towards themes regarding ecology and sus-
tainability in the last fifty years has developed with dif-
ferent intensities in parallel to a series of political and
historical events, such as the first big energy crisis or the
establishment that the hole in the ozone layer exists in
1985 [1]. The concept of sustainability has become a key
idea in national and international discussions following
the publication of the Brundtland Report (1987) and the
1992 Rio ‘Earth Summit’. It was given further promi-
nence in the context of the 2002 World Summit on Sus-
tainable Development held in Johannesburg [2] and with
the most recent Copenhagen Conference of 2009.
Considering the concept of sustainability the building
environment is responsible of almost 40% of the global
emissions. What can be defined as sustainable or eco-
architecture represents an attempt to respond to global
environmental problems and to reduce environmental
impacts due to the building and housing industry, which
include the exhaustion of natural resources, the emission
CO2 and other greenhouse gases [3].
The integration of vegetation on buildings, through
green roofs or vertical greening, allows obtaining a rele-
vant improvement of the building’s efficiency, ecological
and environmental benefits, and it can be an opportunity
to realize more “urban forestry”. The benefits gained
thanks to the use of vegetation are the subject of studies
and researches starting from the seventies [4]. During
this period the first projects which revolved around na-
ture and the environment emerged such as the works of
the SITE group, Emilio Ambasz, Rudolf Doernach, and
Oswald Mathias Ungers.
Green façades offer the potential to learn from tradi-
tional architecture, the earliest form of vertical gardens
dates from 2000 years ago in Mediterranean region, but
also to incorporate advanced materials and other tech-
nology to promote sustainable building functions [5]. It
is a good example of combining nature and buildings
(linking different functionalities) in order to address en-
vironmental issues in dense urban surroundings [6],
since urban centres today are currently searching for
areas to plant vegetation, due to the lack of space, in
order to transform the carbon dioxide produced by traffic
and heating into carbon hydrates and oxygen.
The application of vegetation as a vertical skin can
drastically change its aesthetics and have a positively
K. Perini et al. / Open Journal of Ecology 1 (2011) 1-8
Copyright © 2011 SciRes. OPEN ACCESS
influence on comfort and well being in and around the
building in question [4]. The ecological and environ-
mental benefits regard, as for green roofs, the improve-
ment of air quality and reduction of air pollution, mainly
related to reduction of fine dust levels [7], increase of
biodiversity, the reduction of the heat island effect in
urban areas due to the lower amount of heat re-radiated
by greened façades and the humidity affected by the
evapostranspiration caused by plants and indirect bene-
fits as energy savings for the building. In fact both the
growing medium and the plants themselves provide in-
sulation and shade which can reduce, especially in
Mediterranean area, energy for cooling and improve the
indoor and outdoor comfort [8]. Beside these benefits
also social and economical values are involved, with
respect to the real estate market, the improve of durabil-
ity and better psychological feelings of citizens.
Vegetation can be seen as an additive (construction)
material to increase the (multi)functionality of façades or
buildings. Vertical green, also commonly referred to as a
“vertical garden”, is a descriptive term that is used to
refer to all forms of vegetated wall surfaces [9]. Vertical
green is the result of greening vertical surfaces with
plants, either rooted into the ground, in the wall material
itself or in modular panels attached to the façade and can
be classified into façade greening and living walls sys-
tems according to their growing method [10,5].
Green façades are based on the use of climbers at-
tached themselves directly to the building surface (a), as
in traditional architecture, or supported by cables or trel-
lis (b, Figure 1). In the first case climbers planted on the
base of the building allows to obtain a cheap façade
greening but with possible implications for any building
works that need to be carried out (for example like
damages, maintenance of the façade, see Figure 3), be-
sides that some climbing plants can grow 5 or 6 m high,
others around 10 m and some species at least 25 m [10].
The plant choice affects the aesthetical and functional
aspects of a greened façade. An evergreen plant protects
the façade from wind flow, snow and rain in winter sea-
sons, which can be relevant especially in the temperate
climate or for northern exposed façades. A deciduous
climber allows the building envelope to change visually
and affects also its performances; this type of vegetation
is more suitable for the Mediterranean climate, since in
many cases it is not necessary, even during winter sea-
sons, to have a protection against environmental pa-
rameters and the sun radiation can warm up the building
envelope. Beside this, in the case of an indirect greening
system, where vegetation is supported by cables or
meshes, many materials can be used as support for
climbing plants as, for example, steel (coated steel,
stainless steel, galvanized steel), types of wood, plastic
or aluminium. Each of the materials enumerated changes
the aesthetical and functional properties due to the dif-
ferent weight, profile thickness, durability and cost.
The indirect greening systems can be combined with
planter boxes at different heights of the façade (c, Fig-
ure 1). In this case the system requires, if the rooting
space is not sufficient, nutrients and a watering system.
If nu- trients and a watering system are needed, it can be
de- fined as a living wall system (LWS).
Living wall systems, which are also known as green
walls and vertical gardens, are constructed from modular
panels, each of which contains its own soil or other arti-
ficial growing mediums, as for example foam, felt, per-
lite and mineral wool, based on hydroponic culture, us-
ing balanced nutrient solutions to provide all or part of
the plant’s food and water requirements [10]. The plant
type for these systems is normally evergreen (as small
shrubs) and not naturally growing in vertical. Many sys-
tems have been developed in the last few years, each one
of which with different characteristics, starting from the
growing medium. For example the living wall systems
shown in Figure 2 have different principles of growing
and conceptions: the LWS based on plastic planter boxes
(a) (b) (c)
Figure 1. Direct greening system (a), indirect greening sys- tem (b), indirect greening system combined with planter boxes (c).
K. Perini et al. / Open Journal of Ecology 1 (2011) 1-8
Copyright © 2011 SciRes. OPEN ACCESS
(d) (e) (f)
Figure 2. LWS based on planter boxes (d), LWS based on foam substrate (e), LWS based on felt layers (f).
Figure 3. Examples of possible damages due to the lack of maintenance and to design mistakes.
(HDPE) is filled with potting soil (d), the LWS based on
a foam substrate with steel baskets as support (e) and the
last system shown (f) is a living wall system based on
several felt layers, working as substrate and water proof-
ing, supported by a PVC sheet.
The living wall systems increase the variety of plants
that can be used beyond the use of climbing plants and
offers much more creative (aesthetical) potential. It is
also possible to assume that, from a functional point of
view, most of the living walls systems (LWS), compared
to green, demand a more complex design, which must
consider a major number of variables (several layers are
involved, supporting materials, control of water and nu-
trients, etc.), on top of which they are often very expen-
sive, energy-vorous and difficult to maintain. However
the technology is new, up to now there are less experi-
ences and more detailed investigations in various climate
are needed to optimize the vertical greening systems
Considering the large amount of systems available on
the market in all Europe, it is possible to give an idea of
the costs needed for installing the systems described.
Range of costs for vertical greening systems per m2
(in Euros):
a) Direct greening system (grown climbing plants):
30-45 €/m2
b) Indirect greening system (grown climbing plants +
supporting material): 40-75 €/m2
c) Indirect greening system with planter boxes (LWS):
zinc-coated steel (galvanized steel) 600-800 €/m2
coated steel 400-500 €/m2
HDPE 100-150 €/m2
d) Living wall system based on planter boxes HDPE:
400-600 €/m2
e) Living wall system based on foam substrate:
750-1200 €/m2
f) Living wall system based on felt layers: 350-750
Inside the range given, the costs depend on the façade
surface (equipment) and height, location, connections,
etc. It is clear that the living wall systems are much more
expensive than the direct and indirect greening systems,
this is due to the maintenance needed (nutrients and wa-
tering system), the materials involved, the design com-
plexity. It also has to be ta ken into account the durabil-
ity of the systems, for example a panel of a LWS based
on felt layers has an average life expectancy ten years,
but the LWS based on planter boxes is more durable
K. Perini et al. / Open Journal of Ecology 1 (2011) 1-8
Copyright © 2011 SciRes. OPEN ACCESS
(more than fifty years) [11]. Beside this a thorough de-
sign (de- tails of window ledges, doors, etc.) is necessary
to avoid damages, as corrosion or rot, caused by water
and nutria- ents leakage.
The green layer causes a shading effect, which also
reduces the amount of UV light that will fall on building
materials. Since UV light deteriorates the material and
mechanical properties of coatings, paints, plastics, etc.,
plants will also have an effect on durability aspects. This
is a beneficial side effect which has an influence on
maintenance costs of buildings.
Greening the building envelope with living wall sys-
tems is a suitable construction practice for new building
and retrofitting. In both situations, it is possible to have a
higher integration within the building envelope by com-
bining functionalities. For example in the case of the
conventional bare wall constructed by several layers, it
is possible to skip the outer façade element, since the
protection against the environmental parameters can be
absolved by a living wall system. For retrofitting pro-
jects an external insulation material outside can be easily
covered with LWS panels.
It is possible to classify the various advantages into
main areas, such as aesthetic, environmental and eco-
nomics, even if those are related to each others. Green-
ery improves the visual, aesthetic and social aspects of
the urban area, which have a high influence on the eco-
nomical value of a building or neighbourhood, and con-
tributes to enhancing human health. Urban green is
widely recognized as therapeutic with a number of re-
search studies illustrating this, for example, hospital pa-
tients who can see greenery out of the window recover
more quickly than those who can not [10,12].
The environmental benefits of greening the building
envelope operate at a range of scale. Some of those only
work if a large surface in the same area is greened and
their benefits are only apparent at the neighbourhood or
city scale. Others operate directly on the building scale.
The benefits related to the larger scale regard mainly
the improvement of air quality and urban wildlife (bio-
diversity) and the mitigation of urban heat island effect
[5]. The air quality improvement due to vegetation is
mainly related to the absorption of fine dust particles and
the uptake of gaseous pollutants such as CO2, NO2 and
SO2. Carbon dioxide is used by plants for the photosyn-
thesis process creating oxygen and biomass; nitrogen
and sulphur dioxides are converted into nitrates and sul-
phates in the plant tissue. The fine dust particles (PM),
especially the smaller size fractions (<10 m), are mainly
adhered to the outside of the vegetation parts [7,13];
therefore vegetation is a perfect sink for airborne parti-
cles (Figure 6). Dust particles smaller than 2.5 m are
relevant mainly in the dense urban area because they can
be deeply inhaled into the respiratory system and cause
damages for the human health [14].
Figure 4. Direct greening system (a), indirect greening system (b), indirect greening system combined with planter boxes (c).
Figure 5. LWS based on planter boxes (d), LWS based on foam substrate (e), LWS based on felt layers (f).
K. Perini et al. / Open Journal of Ecology 1 (2011) 1-8
Copyright © 2011 SciRes. OPEN ACCESS
Figure 6. Electron microphotograph of particulate matter
on the upper side of a leaf (Hedera Helix).
The urban heat island (UHI) phenomenon can cause air
temperature in the cities to be 2 - 5°C higher than those
in the surrounding rural areas, mainly caused by the
amount of artificial surfaces (high albedo) compared
with natural land cover [15,16]. Greening paved surfaces
with vegetation to intercept the radiation can reduce the
warming up of hard surfaces. By constructing green fa-
çades and green roofs great quantities of solar radiation
will be adsorbed for the growth of plants and their bio-
logical functions. Significant amounts of radiation are
used for photosynthesis, transpiration, evaporation and
respiration [17]. 5 - 30% of the remaining solar radiation
is passing trough the leaves and is affecting the internal
climate of buildings when it passes the façade or roof. In
the urban area, the impact of evapotranspiration and
shading of plants can significantly reduce the amount of
heat that would be re-radiated by façades and other hard
surfaces. A literature study conducted by Onishi et al [16]
shows a temperature reduction of 2 - 4°C due to the cov-
ering of areas with trees.
The effect of evapotranspiration and shading on the
humidity level and temperature influences also the
building microclimate, indoor and outdoor. As a cones-
quence, especially in warmer climates, the cooling po-
tential can lead to significant energy savings for air con-
ditioning [18]. The cooling potential of green façades or
vertical green is discussed in many studies. Field meas-
urements, conducted in Germany, on a plant covered
wall and a bare wall by Bartfelder and Köhler [19]
shows a temperature reduction at the green façade in a
range of 2-6 °C compared with the bare wall. Another
recent study by Wong et al [8] on a free standing wall in
Hortpark (Singapore) with vertical greening types shows
a maximum reduction of 11.6 °C. This proves that a
greened façade adsorbed less heat then a non greened
façade and reveal itself in less heat radiation in the eve-
ning and night. As shown in the photo below (Figure 7),
taken with an infrared camera in The Netherlands during
summer period (August), the surfaces uncovered (red)
are warmer than the area covered by vegetation (green/
Green façades and living wall systems (LWS) have
different characteristics that can have influence on the
cooling potential above described; beside this it affects
also the insulating properties. This comes, among other
things, due to the thickness of the foliage (creating a
stagnant air layer and shading the façade), water content,
material properties and possible air cavities between the
different layers.
The thermal transmittance (and thus insulation prop-
erties as well) of a building is among other things de-
pendant and affected by the wind velocity that passes the
surface of the building, a green layer can enhance the
thermal properties of a façade. A study conducted by
Perini et al [20] shows the potential of vertical green
layers on reducing the wind velocity around building
façades. Thanks to an extra stagnant air layer, which can
be created inside the foliage, when the wind speed out-
side is the same as inside, Rexterior can be equalized to
Rinterior. In this way the benefit on the thermal resistance
of the construction can be quantified by an increase of
0.09 m²·K·W1. These results refer to the wind speed
measured on a façade covered by a well grown direct
greening system (a, Figure 1).
In the case of living wall systems the insulation prop-
erties of the material used can be taken into account, as
well as the air cavity between the system and the façade
and, in the case of a well grown vegetation, Rexterior can
be equalized to Rinterior, as for the direct greening system;
for example the total thermal resistance of a living wall
system based on planter boxes (d, figure 2) can be esti-
mated as R = 0.52 m²·K·W1. For both green façades
Figure 7. Photo of a façade covered by Boston i vy (Partheno-
cissus) rooted in the soil and applied directly against the
façade taken with infrared camera (Delft, The Netherlands,
summer 2009, 12 p.m., air temperature 21°C)
K. Perini et al. / Open Journal of Ecology 1 (2011) 1-8
Copyright © 2011 SciRes. OPEN ACCESS
and living wall systems, this implies potential energy sav-
ings for building envelopes in warmer and colder climates.
Beside the environmental benefits above described
that greening systems allow to obtain, it is eventually not
clear if these systems (all or some) are sustainable, due
to the materials used, maintenance, nutrients and water
needed. Sustainability can be defined as a general prop-
erty of a material or a product that indicates whether and
to what extent the prevailing requirements are met in
specific application. These requirements, which relate to
air, water and soil loading, have influences on well being
and health of living creatures, the use of raw materials
and energy, and also consequences for the landscape, the
creation of waste and the occurrence of nuisance to sur-
rounding environment [21].
A life cycle analysis can be an effective tool for evalu-
ating the sustainability of a building element, with re-
spect to the integral balance between the environmental
load and the possible benefits. A study conducted by
Ottelé et al. [22], regarding a life cycle analysis of four
greening systems, shows the environmental burden pro-
file in relation with the energy savings for air condition-
ing and heating achievable (according with Table 1),
since only an estimation of the microscale benefits is
taken into account in the research, for a Mediterranean
climate situation and for a temperate climate one. The
four greening systems analyzed in this LCA are: a direct
greening system (a), an indirect greening system (b), a
LWS based on planter boxes (d) and a LWS based on felt
layers (f), the same shown in Figures 1 and 2.
As shown in Graph 1, the energy benefits provided
by the greening options make a noteworthy impact in the
LCA and are calculated for Mediterranean and temperate
climate; for the Mediterranean climate the benefits cal-
culated are roughly two times higher thanks to the en-
ergy savings related to the cooling potential. From this
LCA research it can be concluded that:
The direct greening system has a very small influ-
ence on the total environmental burden, for this rea-
son this type of greening, without any additional ma-
terial involved, is always a sustainable choice for the
examined cases.
The indirect greening system analyzed based on a
stainless steel supporting system has an high influ-
ence on the total environmental burden.
The LWS based on planter boxes has not a major
footprint due to the materials involved, since the ma-
terials affect positively the thermal resistance of the
Table 1. Energy saving (calculated with Termo 8.0 software,
[22]) for heating, energy saving for cooling and tempera-
ture decrease for Mediterranean and temperate climate
based on Alexandri and Jones [18].
Greening systemBenefit Mediterranean
Direct green energy saving for
heating 1.2% 1.2%
temperature de-
crease 4.5°C 2.6°C
energy saving for
cooling 43% ---
Indirect green energy saving for
heating 1.2% 1,2%
temperature de-
crease 4.5°C 2.6°C
energy saving for
cooling 43% ---
LWS planter boxesenergy saving for
heating 6.3% 6,3%
temperature de-
crease 4.5°C 2.6°C
energy saving for
cooling 43% ---
LWS felt layersenergy saving for
heating 4% 4%
temperature de-
crease 4.5°C 2.6°C
energy saving for
cooling 43% ---
The LWS based on felt layers has a high environ-
mental burden due to the durability aspect and the
materials used.
Since the development in this field is growing rapidly
especially the last three to four years, many systems with
different materials and characteristics are available. The
different systems and materials can have an influence on
the environmental burden either positively and nega-
tively. For example for the indirect greening system also
other materials can be used as support for climbing
plants, such as different types of wood, plastic, alumi-
num and steel, instead of a stainless steel mesh, and can
have an influence on the environmental burden of the
system roughly 10 times lower than the stainless steel
mesh [21]. Beside this for living wall systems a sustain-
able approach can involve a higher integration within the
building envelope by combining functionalities, since
the protection against the environmental parameter can
be absolved by the layers involved.
Greening the building envelope, considering the ma-
terials involved, that have a high influence on the envi-
ronmental profile, and taking into account all the bene-
fits (also the ones not quantifiable yet) is a sustainable
option for new constructions and retrofitting.
Vertical greening systems and theirs environmental
benefits are the subject of stdies and researches starting u
K. Perini et al. / Open Journal of Ecology 1 (2011) 1-8
Copyright © 2011 SciRes.
Graph 1. Total environmental burden (impact) for four greening systems (supporting systems + vegetation), benefits for
heating and cooling for Mediterranean climate and benefits for heating for temperate climate according to Ottelé et al. [22].
from the seventies [4]; however it has not been approved
as an energy saving method for the built environment.
The most of the studies have been conducted about
green façades (base on climbing plants), but still even
those concepts are not fully investigated. Many re-
searches can be deepened for quantifying the environ-
mental benefits especially for the macroscale. Recent
technical solutions are under development for vertical
greening systems, as defined living wall systems (LWS).
This is a new field to investigate, regarding the insula-
tion properties, durability aspects, maintenance, plants
choice related to the climate conditions, materials in-
volved, etc. The systems design can take into account
many aspects, such as the integration with the building
envelope, a sustainable material choice considering the
environmental impact but also the symbiosis between
the growing medium and the vegetation, which is a key
element for the success of the greening system. Also the
economical aspects, related to costs savings due to pos-
sible reduction of energy needed for heating and cooling,
have to be taken into account for avoiding a larger use of
green envelops in the urban area. A process tree can be
developed for urban design, new constructions and ret-
rofitting projects, to afford the right choice of greening
system, considering the main parameters, as the climate
type and building characteristics, to avoid damages and
maintenance problems caused by an inappropriate design.
The multiple benefits of vertical greening systems could
allow to a more sustainable urban design and to com-
pensate the lack of green spaces inside dense cities for
the wellbeing of the dwellers.
Department of Materials and Environment of Delft University, Fac-
ulty of Civil Engineering and Geosciences are acknowledged for the
availability to allow a international cooperation with University of
Genoa. The Department of Architectural Sciences of University of
Genoa, Faculty of Architecture is acknowledged for the necessary
financial support for the international cooperation.
Barbera Peters and Ben Vriesema are acknowledged for theirs pho-
tographs used in this article.
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