How successfully do green facades enhance urban environmental conditions and to what extent is this
approach sustainable?
Context
‘Unless one merely thinks man was intended to be an all conquering and sterilizing power in the world, there
must be some wise principle of coexistence between man and nature, even if it has to be a modified kind of
man and a modified kind of nature.
This is what I understand by conservation’ (Elton, 1958; p. 145). 1
IN ALL RESPECTS A BARRIER OF SORTS? AGAINST PARTICULATE POLLUTION, NOISE POLLUTION, HEAT, HEAT
TRANSFER, WIND,
The concept of greening our buildings with plants is by no means a new and original idea. Indeed, the concept
has been integral to buildings for thousands of years. First, we may consider the Mediterranean region, where
2000 years ago palaces were found to be covered with vines for they were known to shade the buildings, their
evapotranspirative cooling properties, economic value for the growth of fruits, and aesthetic improvement
through ornamentation.2 In Northerly regions of the world though, vernacular architectures developed using
turf to line roofs and walls as a readily available and effective insulation. This can be seen in the ancient
structures of Jarlshof in the Shetland Isles. Here the settlement, of which the earliest parts are 4000 years old,
small tight stone structures were erected which were once covered with turf to protect against the harsh
North Sea wind.
In more recent years however, the greening of facades re-emerged in the 19th century as a response to the
industrialisation of cities. This was also the inspiration for Ebenezer Howard’s Garden City Movement which
addressed the deterioration of cities and quality of life through a rationalised plan balancing industry,
agriculture and housing for the ‘ideal’ city arrangement.3 The implementation of vegetation within cities was
the “first ecological reaction to industrialisation”4
Contemporary thought however originates from the
increased awareness of global warming, climate
change and the potential for sustainability, which was
promoted by German artists such as Hundertwasser
in the 1970s, as suburbanisation increased and inner
cities demanded redevelopment.5
http://www.hundertwasser.at/images/hundertwasser/oeko/apa_0343.jpg
1
‘Urban reconciliation ecology: The potential of living roofs and walls’ from Journal of Environmental
Management (2009) Francis, R. A., Lorimer, J.
2
Köhler, M. “Green Facades – a view back and some visions” Urban Ecosyst (2008) p.423
http://www.architecture.com/HowWeBuiltBritain/HistoricalPeriods/TwentiethCentury/GardenCityMovement
/PlanOfAnIdealGardenCity.aspx#.UlkunlC-2uI [Accessed: 12/10/13]
4
Kaltenbach, F., “Living Walls, Vertical Gardens – from the Flower Pot to the Planted System Facade,” Detail 12
(2008): 1455.
5
Köhler, M. “Green Facades – a view back and some visions” Urban Ecosyst (2008) p.424
3
The construction of green facades was thus endorsed, especially in Germany, with a strong incentive
programme initiated in Berlin resulting in the construction of 245 584m 2 green facades installed in the years
1983-97.6
Green buildings – appearance of green – misconceptions associated with this – misleading to both general
public and professionals alike.
Reduce history to 100 words, and then:
- psychological benefits
It may not be actively acknowledged or considered however it is an essential part of our instinct for
human survival that vegetation affects our psychological well-being.
- global scale/urban landscape
- outline spectrum of attitudes:
< aesthetic to scepticism >; glossy Patrick Blanc > Paradise Passage
http://2.bp.blogspot.com/-S7CU7gWyFnc/TcL7VemKeI/AAAAAAAAAXM/3ux1pTGMmQ0/s1600/caixa_forum_madrid_9.jpg
http://www.architectsjournal.co.uk/pictures/636xAny/2/9/1/1232291_DSDHA_Paradise_Park.jpg
Various systems:
First patented system – US Stanley Hart White 1938, Vegetation-Bearing Architectonic Structure and System
The various environmental conditions affected by the implementation of green vertical systems:


6
Ibid.
Thermal – cooling /insulation
Light (seasons)

Air


o Movement
o Pollution
o Wind / bioprotection
Moisture/rain
Sound – dampens noise pollution - insulation but also has its own noise to cover
Passive energy system for:




Shade
Insulation by vegetation and substrate
Evaporative cooling
Barrier to wind
In this section the aim is to demonstrate the potential benefits and weaknesses of vertical green systems. A
pressing issue in the analysis of this performance is however the variables which may influence the results,
which is the source of difficulties in offering clear comparisons to the different systems. 7 It should be noted
that the following represents an overview of the effects of green walls but that in each case climate, plant
variety, immediate context, type and material of system implemented should also be considered.
The thermal benefits of green facades and living wall systems, whether for the cooling or insulating properties
of the wall are depended on the variables of foliage thickness, water content, structural properties and air
spaces between the leaves.8
Shade
It is not a new concept to build near vegetation to aid in building cooling. Plants naturally grow with and
respond directly to the seasons, thus it is logical to consider exploiting the intelligence of the natural façade as
a way condition our buildings. “seasonal variation of the shading effect” 9
The absorption of the solar radiation by the plants is also essential to their “biological functions” for
photosynthesis, transpiration, evaporation and respiration, with only 5-30% of the solar radiation incident on
the facade actually reaching the wall behind the foliage. 10 Shading and evapotranspiration can considerably
decrease the heat which would be re-radiated by other hard surfaces in the urban environment. INDEED
“every 0.5° internal temp difference can reduce the electricity use for air conditioning up to 8%” 11
7
Gabriel Pérez, Lídia Rincón, Anna Vila, Josep M. González, Luisa F. Cabeza, Green vertical systems for
buildings as passive systems for energy savings, Applied Energy, Volume 88, Issue 12, December 2011, pp.
4854
8
Katia Perini, Marc Ottelé, A.L.A. Fraaij, E.M. Haas, Rossana Raiteri, Vertical greening systems and the effect on
air flow and temperature on the building envelope, Building and Environment, Volume 46, Issue 11, November
2011, Pages 2287
9
Kenneth Ip, Marta Hoi-Yan Lam, Andrew Miller Assessing the shading performance of climbing plant
canopies for the PLEA2007 The 24th Conference on Passive and Low Energy Architecture
10
Katia Perini, Marc Ottelé, A.L.A. Fraaij, E.M. Haas, Rossana Raiteri, Vertical greening systems and the effect
on air flow and temperature on the building envelope, Building and Environment, Volume 46, Issue 11,
November 2011, Pages 2288
11
Katia Perini, Marc Ottelé, A.L.A. Fraaij, E.M. Haas, Rossana Raiteri, Vertical greening systems and the effect
on air flow and temperature on the building envelope, Building and Environment, Volume 46, Issue 11,
November 2011, Pages 2288
Studies have shown that the solar radiation is two times lower when using a secondary façade of vegetation as
opposed to a façade which only has blinds, not only because it is a more effective shading device but also
because plant surfaces will never exceed 35°C, while blinds can reach above 55°C. 12
The “Bioshader” Experiment conducted by the University of Brighton in 2003 investigated the “thermal
shading performance of a vertical layer of deciduous climbing plant canopy”, in which two identical offices
were selected as test and control rooms. To the test room’s windows external stainless steel frames were
attached to the frame onto which Virginia Creeper plants were grown. Occupation of these rooms during the
experiment also remained constant.
Tests concluded that solar transmittance varied between 0.43 and 0.14, for up to five layers of leaves and one
layer respectively, and that the internal temperatures were reduced 3.5 – 5.6°C.
pp. 47-48 Green Design: Agnes Novak: the leaves “follows the daily and annual cycles optimally providing the
following advantages: in summer – when the sun is high – leaves of the plant rise up operating as ventilating
shutters providing a stack effect between the building and the plant and cooling the air that enters the house.
Contrary to this, in winter – because of the low sun position – leaves of the evergreen carpet turn down – low
hydrostatic pressure can be observed – and stick together, enclosing a stationary insulating air layer.”
Manfred Köhler revealed that the density of leaves will vary the results; through experiment he concluded that
Ivy is the most efficient in this respect, as it provides a shadow effect similar to that produced by trees. 13
The results of a test carried out in Holland to determine the relative efficiencies of various vertical greenery
systems (that is, direct greening system, indirect, and living wall system) recorded the wind speed and
temperature differences induces by the differing systems.
Evaporative cooling by evapotranspiration
Dependent on the type of plant and exposure, and climate (dry/windy increase effect), and in the case of LWS
the substrate will impact the effect of this also.
In referring to Wong, Perez et al. notes that external insulation is more effective than internal and thus VGS
can work on two levels to reduce energy consumption: through reducing solar energy through shading, and
reducing heat flow through evaporative cooling. 14
12
Gabriel Pérez, Lídia Rincón, Anna Vila, Josep M. González, Luisa F. Cabeza, Green vertical systems for
buildings as passive systems for energy savings, Applied Energy, Volume 88, Issue 12, December 2011, pp.
4856
13
Pérez, G., et. al. Green vertical systems for buildings as passive systems pp. 4856
“The cooling effect mediated by transpiration relies on the presence of a healthy plant cover sustained by
adequate irrigation.”15 Current literature records that daily temperature changes can be dramatically reduced,
with 40-80% of incident radiation reflected or absorbed, and converted to latent heat, which does not result in
a rise of temperature.16 Such considerable temperature differentials are however likely to be more typical of
hotter climates. This is nonetheless important especially in the discussion of heat mitigation in dense urban
environments, where buildings will as common practice utilise air conditioning units. The same report
referenced another study where energy reductions for air conditioning were reduced 23%, with an annual 8%
saving in energy use17.
UHI and urban canyon effect
Insulation
In addition to cooling in the summer through shading of the facade, vertical greenery systems are also
considered an effective means of further insulating a building in creating a stagnant layer of air between the
vegetation and facade. Conducted in autumn, very little temperature difference was noted; this was true for
another study by Köhler in Germany during a similar time. With warmer temperatures however considerable
temperature differences have been recorded of up to 6°C. (31.0 for bare façade, 25.2 for greened façade).
This is indication for the intuitive nature of the planting screen though as it is influenced directly by the
environment and consequently can condition the building as demanded by the local climate. 18
As with the cooling effects of the vegetation on buildings, it has been proven by Holm in 1989 that this is most
effective in “low-mass buildings in hot-arid climates” on walls facing towards the equator.19 However even in
more temperate climates experiments reveal peak cooling load transfer can be reduced by up to 28% in
summer. As the vegetation reduced the incident solar radiation to the facade, it also reduces the exposure of
the facade to the immediate external environment during winter, thus significantly lowering the energy
transfer. Köhler reported that insulation could provide up to 5°C internal temperature difference compared to
an uncovered facade.
wind
The study of the three Dutch facades by perini et. al. Also demonstrated a decrease in wind speed of between
0.43m/s and 0.55 m/s compared to 10 cm in front of the facade. Wind was recorded in the cavity of the
indirect climber system and not in the LWS, this is due to the density of the materials (felt, plastics etc.). The
drop in wind velocity is still a sign of the potential of green facades as a protective barrier, which can both
14
Gabriel Pérez, Lídia Rincón, Anna Vila, Josep M. González, Luisa F. Cabeza, Green vertical systems for
buildings as passive systems for energy savings, Applied Energy, Volume 88, Issue 12, December 2011, pp.
4857
15
C.Y. Cheng, Ken K.S. Cheung, L.M. Chu, Thermal performance of a vegetated cladding system on facade
walls, Building and Environment, Volume 45, Issue 8, August 2010, Pages 1787
16
Nyuk Hien Wong, Alex Yong Kwang Tan, Yu Chen, Kannagi Sekar, Puay Yok Tan, Derek Chan, Kelly Chiang,
Ngian Chung Wong, Thermal evaluation of vertical greenery systems for building walls, Building and
Environment, Volume 45, Issue 3, March 2010, Pages 663
17
Nyuk Hien Wong, Alex Yong Kwang Tan, Yu Chen, Kannagi Sekar, Puay Yok Tan, Derek Chan, Kelly Chiang,
Ngian Chung Wong, Thermal evaluation of vertical greenery systems for building walls, Building and
Environment, Volume 45, Issue 3, March 2010, Pages 663
18
Katia Perini, Marc Ottelé, A.L.A. Fraaij, E.M. Haas, Rossana Raiteri, Vertical greening systems and the effect
on air flow and temperature on the building envelope, Building and Environment, Volume 46, Issue 11,
November 2011, Pages 2291
19
C.Y. Cheng, Ken K.S. Cheung, L.M. Chu, Thermal performance of a vegetated cladding system on facade
walls, Building and Environment, Volume 45, Issue 8, August 2010, Pages 1787
protect the fabric of the building itself (bioprotection) but also minimise thermal transmittance induced by
wind directly passing the building envelope. 20 This was also the conclusion of another report which considered
the “prolonged lifespan of building facades” and reduced maintenance to the facade construction itself, but
did not balance the argument with maintenance of the vertical greenery system.
VERY DIFFICULT TO ANALYSE DUE TO VAST VARIABLES. For the system is intrinsically based in the context. ...
The same experiment also revealed that the thermal resistance of the wall construction of the direct greened
facade was increased 0.09m2K/W, which would reduce energy costs. Interestingly the investigations concluded
that the 200mm gap between the foliage and facade of the indirect system was too deep to perform as a
stagnant air layer, and thus would be more efficient if this distance was reduced to obtain “optimal thermal
qualities”.21 Looking at the example of the LWS it noted that there is potential to determine an optimum air
cavity in green facade construction, similar to general wall construction, with an optimum of 40-60mm. The
LWS also has the additional benefits over the other systems of the thermal resistance of the support materials
(planter boxes, felt etc.). –MISLEADING – read this data, believe better, but must also consider other variables
of cost and maintenance, and balance the benefits.
Dust Mitigation
With increased urbanisation and industrialisation our present towns and cities have become clogged with
pollutants. These particles fill the air around us, and can be detrimental not only to our health but that of the
urban fabric too. Vegetation is considered a ‘particulate sink’ whereby fine and ultra fine particles adhere to
the leaf surfaces, thus mitigating them from the air around us. Greater potential compared to a green roof
(area). “vegetation is an efficient sink for particulate matter” 22 particulate capacity depends on plant variety,
structure of vegetation, exhibition , location and circumstances (micro climate).23 Quite unbelievable that :
“The United Nations states that 600 million urban residents worldwide are exposed to harmful levels of trafficgenerated air pollutants, with more premature deaths caused by pollutants in vehicle emissions than by car
accidents (WHO, 2000)”
If vegetation acts as a particulate sink there is greater incentive to enhance greenery of urban environments.
Studies have shown that leaves certainly do pick up the particulate matter from the air around them. One
study into the dust mitigation of Ivy revealed that the under layers of leaves showed considerably less
pollution than those of the outer layers and so it can be proven that it could act as a barrier /bioprotective
layer: “While much debate about ivy concentrates on its deteriorative role, ivy's high absorption rate of fine
and ultrafine particulates points to its pollution reduction role.”24
20
Katia Perini, Marc Ottelé, A.L.A. Fraaij, E.M. Haas, Rossana Raiteri, Vertical greening systems and the effect
on air flow and temperature on the building envelope, Building and Environment, Volume 46, Issue 11,
November 2011, Pages 2291
21
Katia Perini, Marc Ottelé, A.L.A. Fraaij, E.M. Haas, Rossana Raiteri, Vertical greening systems and the effect
on air flow and temperature on the building envelope, Building and Environment, Volume 46, Issue 11,
November 2011, Pages 2293
22
Marc Ottelé, Hein D. van Bohemen, Alex L.A. Fraaij, Quantifying the deposition of particulate matter on
climber vegetation on living walls, Ecological Engineering, Volume 36, Issue 2, February 2010, Pp. 155
23
Troy Sternberg, Heather Viles, Alan Cathersides, Mona Edwards, Dust particulate absorption by ivy (Hedera
helix L) on historic walls in urban environments, Science of The Total Environment, Volume 409, Issue 1, 1
December 2010, Pages 162
24
Troy Sternberg, Heather Viles, Alan Cathersides, Mona Edwards, Dust particulate absorption by ivy (Hedera
helix L) on historic walls in urban environments, Science of The Total Environment, Volume 409, Issue 1, 1
December 2010, Pages 167
Bioprotection or biodeterioration? (Ivy) Mediator between the facade and extreme conditions? 25
“Roots can break through waterproof seals and penetrate the smallest crevices of brickwork. Tendrils can
force their way behind cover strips and window abutments, while leaves and twigs may block rainwater pipes
and gutters. Plantings can also impose an additional load on an outer wall and have a negative effect on the
structural balance.”26
Insulation of frost in January/heat reduction in summer “spikes”
Ivy is an innately hardy plant: resilient against frost, shade, drought and pollution. Max temp difference
recorded in summer of 17°C in summer. Deterioration can be caused through forced exertion of roots into the
building materials or “chemical decomposition as they can secrete acids and other compounds” 27. The same
study revealed (although not conclusive) that ivy will only root into the wall if there is a hole there existing/has
been encouraged by attempts to kill the plant. Indeed ivy is invasive, and hardy, and can break through under
walls and into cavities. However studies by English Heritage and the University of Oxford demonstrated that
aerial roots cause little damage to stone, and their presence is more ‘superficial’. 28 Growing plants be may
good for some kinds of walls and not for others – this requires further investigation.
Acoustics
It was reported in 2000 that 44% of the population in the EU was exposed to road traffic noise levels of more
than 55 dB.29 Research on the effectiveness of vertical greenery in sound mitigation is limited, however the
effects of ground and roofing vegetation have been written about more extensively. Indeed, Wong et. Al. in
referring to Schroeder noted a 5-20dB sound reduction from the presence of a roof garden.
“The WHO reported “burden of disease by environmental noise” quantified the many health-related effects by
long-term exposure to environmental noise. 30 Our cityscapes are composed of hard materials, of brick,
masonry, concrete and glass which are unforgiving, amplifying high sound pressure levels. Experiments have
been conducted to ascertain the performance of green facades as a means of mitigating sound levels; the wall
is essentially a buffer (as with the thermal insulative properties) and can considerably reduce the noise of our
towns and cities, mainly emitted by traffic.
Studies have demonstrated effective use of green walls in street canyons, and interestingly it has been noted
that a more considerable difference in sound levels was recorded in streets adjacent to the street canyons
25
Troy Sternberg, Heather Viles, Alan Cathersides, Evaluating the role of ivy (Hedera helix) in moderating wall
surface microclimates and contributing to the bioprotection of historic buildings, Building and Environment,
Volume 46, Issue 2, February 2011, Pages 293
26
Kaltenbach, F., “Living Walls, Vertical Gardens – from the Flower Pot to the Planted System Facade,” Detail
12 (2008): 1454.
27
Ivy on walls seminar oxford university pp.29
28
Ivy on walls seminar oxford university pp.30
29
Nyuk Hien Wong, Alex Yong Kwang Tan, Puay Yok Tan, Kelly Chiang, Ngian Chung Wong, Acoustics
evaluation of vertical greenery systems for building walls, Building and Environment, Volume 45, Issue 2,
February 2010, Pages 411
30
Timothy Van Renterghem, Maarten Hornikx, Jens Forssen, Dick Botteldooren, The potential of building
envelope greening to achieve quietness, Building and Environment, Volume 61, March 2013, Pages 34
implemented with the green façade as much of the direct sound still reaches the receiver in the greened street.
31
It is very difficult to analyse noise transmission in urban canyons due to the variables of a variety of reflective
surfaces, of varying heights and shapes etc.32 In a study investigating the noise in courtyards when using green
walls as a source of sound mitigation, it was found that greening the upper halves of the facades was more
effective – it was the edges which were most important in sound reduction, and also when used with harder
materials such as concrete or masonry compared to softer bricks. 33 Greening of the courtyard sides was
proven more effective than of the street canyon side in reducing sound levels in the court. In the same study
however green roofs were proven more effective, or even a combination of green roofing and wall strategies.
A study conducted in Singapore in 2010 recorded that vegetated walls are most effective for higher
frequencies of sound (between 200Hzto 1kHz), however the substrates of living walls performed better with
lower frequencies, as it absorbed the acoustic energy reducing the reverberation time. The same study also
recorded however that course concrete block outperformed the vegetated walls for low frequencies. 34
It is important to consider the type of vegetated wall system utilised if for the purpose of mitigating noise
pollution, as not all systems are effective. It is important to consider and test the effects with more conclusive
results to that which is currently available, and test the variables of structure, materials, panel dimensions,
type, compositions, depth and moisture content of substrate, and the type of plant.
IRRIGATION!!!!
LIMITATION OF HEIGHT OF PLANTS- GROWTH
BIODIVERSITY
CASE STUDIES
Patrick Blanc and his ‘Mur Végetal’
Patrick Blanc, a French botanist, comes from a scientific background, yet channels his passion for art, botany
and the urban environment through his patented “invention” of the vertical garden from 1988 (which as we
mentioned before was possibly first patented by Stanley Hart White). Nevertheless, today it is Patrick Blanc
with whom we strongly associate the vision of LWS with.
Blanc challenged the traditional methods of vertical greenery in the 1980s, which were hindered by the
logistics of suspending the sheer weight of the planter boxes containing earth soaked in water. Having
travelled young to Malaysia he investigated how plants thrived on rock with little or no soil. He suggested that
plants would be able to grow sufficiently even in temperate climates when only the roots were covered with
31
Timothy Van Renterghem, Maarten Hornikx, Jens Forssen, Dick Botteldooren, The potential of building
envelope greening to achieve quietness, Building and Environment, Volume 61, March 2013, Pages 34
32
Timothy Van Renterghem, Maarten Hornikx, Jens Forssen, Dick Botteldooren, The potential of building
envelope greening to achieve quietness, Building and Environment, Volume 61, March 2013, Pages 35
33
Timothy Van Renterghem, Maarten Hornikx, Jens Forssen, Dick Botteldooren, The potential of building
envelope greening to achieve quietness, Building and Environment, Volume 61, March 2013, Pages 40
34
Nyuk Hien Wong, Alex Yong Kwang Tan, Puay Yok Tan, Kelly Chiang, Ngian Chung Wong, Acoustics
evaluation of vertical greenery systems for building walls, Building and Environment, Volume 45, Issue 2,
February 2010, Pages 418
adequate water and nutrients – and that this could be stored within substrates. This hydroponic cultivation,
without soil, however is not simple, and the substrate and structure is complicated. 35
Le Mur Vegetal consists three elements: metal frame hung from or standing separate to the wall, 10mm thick
PVC sheet for rigidity and waterproofing, and a layer of polyamide felt: the substrate for the vegetation which
allows even distribution of water.36 Irrigation is fed from the top into the substrate through drip, in which
nutrients are also provided. The entire system is <30kg/m2 which allows it to be integrated into facades with
no limitation to size or height.
Blanc assures that the LWS presents no threat to biodeterioration of the existing facades, as roots are
embedded in the felted substrate, an element separate from the façade structure, a second skin. However this
does not mean that they are not invasive beings – the living wall is different to all other “cladding” systems
because it is living. This means that it demands maintenance and care to ensure its success, as failure would
result in the ‘death of the wall’.
Le Mirage Verde – the green mirage - 5 Rue de Marignan, Paris. Invasive?
Blanc is an artist at heart – the building envelop is his canvas. Although he makes claims of the ecological effect
of the living wall systems, this is not the emphasis of his work – it has a different ambition, for uniting nature
and architecture, and improving the appearance of the urban environment.
However the initial and life-cycle costs of these Living Wall Systems is very much glazed over. While LWS may
present (in some cases) the most efficient ecological system in terms of sound absorption or thermal
conditioning of the buildings, they are currently not economically viable solutions. Indeed this aspect of the
design is criticised as “play[ing] no useful ecological role” and quite harshly as “a commercially driven synthesis
of aesthetic and morphological elements removed from their original context”.37 This is true of many building
materials today – timber and stone is imported world-wide to achieve ‘that look’ without question of the
context. Criticisms such as this fail to acknowledge the variety of benefits that façade greenery can perform,
for urban sustainability should not only address energy reductions but also the psychological bearings of our
urban fabric on society. Blanc’s work is more aligned to the therapeutic role which vegetation can play within
society as opposed to the ecological benefits.
However this is not the ideal message of sustainability being broadcasted by the urban environment - with the
importing of tropical species for many of his designs.
Studies in cost-benefit analysis reveal that LWS such as those designed by Patrick Blanc can cost up to £1000,
depending on the façade surface, height, location and connections. However this does not end with the initial
set-up costs, as the LWS require more maintenance than other forms of vertical greenery systems.
4. Living wall system
Initial Plant species One time 27.49
Panels and transportation One time 176.23
Irrigation system One time 27.61
Installation One time 83.50
35
Kaltenbach, F., “Living Walls, Vertical Gardens – from the Flower Pot to the Planted System Facade,” Detail
12 (2008): 1457
36
‘A Scientific and Artistic approach by Patrick Blanc’ from http://www.verticalgardenpatrickblanc.com/
accessed: 13/10/13.
37
Gandy, M. (2010), The Ecological Facades of Patrick Blanc. Architectural Design, 80: pp.33
Maintenance Pruning and panels adjustment Annual 14.41 – for the study around £4200 maintenance during
lifespan
Irrigation (H2O) Annual 0.96
Panels replacement (5%) Annual 6.05
Plant species replacement (10%) Annual 2.75
Pipes replacement (irrigation system) Annual 2.85
Cladding renovation One time e 50th year 486.96
Disposal Green layer disposal One time e 50th year 218.56
2B. Steel indirect green façade Initial Plant species One time 1.52
Dig þ pot One time 36.27
Supporting system and transportation One time 93.79
Installation One time 83.50
Maintenance Pruning Annual e after 4th year 2.81
Cladding renovation One time e 50th year 755.39
Disposal Green layer disposal One time e 50th year 199.74
1. Direct green façade
Initial Plant species and installation One time 21.78a/m length of base
Dig þ pot One time 519.92a
Maintenance Pruning Annual e after 4th year 2.81
Cladding renovation One time e 50th year 1224.35
Disposal Green layer disposal One time e 50th year 31.1038
The same study concludes that the living wall system does not present a viable system for sustainability. It is
by far the most expensive installation, in initial set up, and maintenance (and replacement etc.) which does not
repay sufficient benefits (both economical and social) to justify the use of the system. In fact is it calculated
that economic benefit comes in the 50th year – the year of disposal/ replacement.


38
DIRECT GREEN FAÇADE PBP 20years
Indirect - HDPE better than steel mesh – for the former PBP 16 years (best)39
Katia Perini, Paolo Rosasco, Cost–benefit analysis for green façades and living wall systems, Building and
Environment, Volume 70, December 2013, Pages 114
39
Katia Perini, Paolo Rosasco, Cost–benefit analysis for green façades and living wall systems, Building and
Environment, Volume 70, December 2013, Pages 120