With an ever increasing demand on the built environment to meet EU carbon emission targets, why are green facades – given
their potential benefits – not implemented more extensively in the UK?
Carbon Emission Targets
It has become a global concern that with greater urbanisation and the unsustainable consumption which
is part of this. Cities may cover only 2% of the earth’s surface, but within those cities live 50 % of the
world’s seven billion people who account for 75% of humanity’s annual resource consumption.1
Accounting for 30-40% the world’s carbon emissions is the construction industry and built environment.2
To slow down the effects of climate change, the EU established levels for Greenhouse Gas Emissions
(GHG) to be reduced by 80-95% by 2050, from the 1990 figures.3
The Climate Change Act 2008 passed in the UK set legally binding targets for at least 80% reduction of
emissions. The road map for meeting these targets primarily addresses waste and efficiency of
infrastructure and the built environment.
Given that 43% the UK’s GHG is derived from building heat loss and wasted energy,4 the Built
Environment Routemap outlines a strategy employing “proven and cost effective technologies”5 to help
tackle these changes. While this shows that the government is committed to reducing energy
consumption and carbon emissions, it indicates a missed opportunity to integrate green facades within the
overall strategy as they are rightly “not an optional extra, gimmick or passing fancy but one element of a whole suite of
measures which should be used to restore ecosystems and help us move towards life within natural limits.”6
Potential Environmental Benefits
“A roof or external wall can be more than just a weatherproof surface or structural element – it can be a living, cooling,
cleansing skin.”7
This section of the report aims to outline the potential ecological benefits of employing vegetated façade
systems within a temperate climate such as the UK.
Grant, G., Ecosystem services come to town pp. , 5
Low Carbon Routemap for the UK Built Environment, 5 Mar 2013, the Green Construction Board pp. 14
3 http://ec.europa.eu/clima/policies/brief/eu/index_en.htm
4 https://www.gov.uk/government/policies/helping-households-to-cut-their-energy-bills/supporting-pages/greendeal
5 The Carbon Plan: Delivering our low carbon future, HM Govt, December 2011, pp. 4
6 Grant, G., Green Roofs and Façades, IHS BRE press, 2006 pp. ix.
7 Grant, G., Green Roofs and Façades, IHS BRE press, 2006 pp. 2.
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Plants naturally respond to diurnal, seasonal and climatic changes to maximise efficiency of
photosynthesis, transpiration, evaporation and respiration; these innate biological functions can intuitively
work with building systems to help naturally cool, shade and protect the building and its occupants. As
illustrated in Fig X, the leaves of the evergreen plant will close during winter to enclose a stagnant
insualtive layer and perform as a wind break, reducing air flow directly at the façade, which can be a factor
increased heat flux and energy loss from UK buildings.8 In summer the leaves open and climb towards
the sun as a part of phototropism, and allow the air gap to be ventilated, and cooled with the water
vapour product of evapo-transpiration.9
Foliage is an effective shading device for summer use due to its low surface temperature, and high
absorbance of solar radiation. Indeed 5-30% of incident radiation reaches the wall behind the foliage
while 5-20% is used for photosynthesis a, 10-50% is converted into latent and sensible heat, with only 530% reflected.10 This reduces reliance on mechanical plant to cool the buildings, and though is dependent
on leave and foliage density and is more efficient in hotter climates, has been shown to reduce internal
temperatures in the UK by 3.5 – 5.6°C.11
Green façades can help in the drainage of dense inner cities where the non-porous materials of the built
environment restrict water from running into the land. Integrated into urban planning such measures can
help to alleviate the effects of flash flooding. Green facades are however less efficient at doing this than
green roofs due to the area of catchment, and are required water storage containers to be integrated into
the design, however this can be utilised as part of the irrigation system.12
UK cities, particularly London, are not excluded from the phenomenon of the Urban Heat Island Effect
(UHIE) and though may not experience this as severely as hotter climates temperatures are still amplified
within street canyons with reduced air flow. Through evapo-transpiration and the comparatively softer
surface of foliage to the hard materials of the built environment, vertical greenery systems can successfully
mitigate heat in dense city environments such as London by between 1.7°C and 3.2°C, still benefitting
occupants unused to temperature fluctuations. 13
Plants also naturally improve air quality through CO2 absorption and O2 production, but are also adept at
mitigating particulate matter in the air. Controversy arose in 2012 when it was revealed that the UK
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
9
Studies generally refer to the cooling potential of plants in hotter
10 M. Ottelé et al. / “Comparative Life Cylce Analysis for green façades and living wall systems” Energy and
Buildings 43 (2011) 3420
11
University of Brighton Bioshader experiment
12
Köhler, M., A view back and some visions - 7
13 E. Alexandri, P. Jones / Building and Environment 43 Temperature decreases in an urban canyon due to green walls and
green roofs in diverse climates (2008) 490-91
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breached NO2 and Particulate Matter (PM) levels in 34 or its 43 zones, with some critical zones showing
no improvement in fifteen years.
Worryingly, “air pollution is the biggest public health risk after smoking” which causes asthma in children,
putting the over 65s at risk of cardiovascular disease. In 2010 London had the fourth highest levels of
PM2.5 and PM10 in the EU and the “highest annual mean concentrations of NO2, a toxic gas, of any
capital city in Europe”14 to a degree that it was comparable with Beijing in 2008.
Particulate matter sticks to stomata on leaves which are then either dropped during autumn or washed to
the ground in rain identifying the system as key choice for reducing air pollution in UK cities. The
effectiveness of the leaves is dependent on the variety, density and surface area and the most efficient
plants are still disputed making application difficult.15
“Biodiversity loss is moving ecological systems ever closer to a tipping point beyond which they will no longer be able to fulfil
their vital functions.” UN Secretary-General Ban Ki-moon, International Day for Biological Diversity, 22
May 2010.16
Increased urbanisation also endangers the sustainability of the natural world as the built environment
takes over important habitats of flora and fauna which are integral to the British ecology.17 With an
increasing shortage of space in urban contexts the logical solution is to green then next greatest surface
area city environments – the facades of buildings – which can form habitats for various birds, insects and
invertebrates. 18
The range of opportunities offered by the implementation of green facades in reducing the dependence
upon mechanical systems is clear; however it must be clear of the ambitions of the project, and the
intentions for its employment, to ensure successful sustainability. Proven as a legitimate passive device, it
suggests that other factors are responsible for their tentative emergence in the UK.
Social Interaction
‘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). 19
There has long been a historical and romantic attachment to the idea of ivy covered buildings and ruins in
rural settings. However since the urbanisation of the industrial revolution, man and nature become more
detached. In response to this separation Ebenezer Howard’s Garden City Movement (1899) acknowledged
the societal benefits of the union and harmony of town and country though in a very idealistic and
utopian context.
http://cleanairinlondon.org/wp-content/uploads/CAL-187-EC-rejects-time-extensions-in-12-UK-zones2806122.pdf
15 Shackleton, K., Smith, H., Davies, L., Bell, N., The role of shrubs and perennials in the capture and
mitigation of particulate air pollution in London. Imperial College London.
16
M&s ambitions biodiversity p 6
17
M&s ambitions biodiversity p 5
18
Köhler, M., A view back and some visions - 7
14
19
Urban reconciliation ecology: The potential of living roofs and walls 1429
3
The global awareness of climate change, depleting resources and dense cities became apparent in the
1970s triggered the contemporary attitude to ecologically driven buildings. This drove the search for
technically viable systems uniting buildings and greenery as “spaces and surfaces that were previously
considered too marginal or technically challenging to warrant much in the way of sustained
attention.”20 This was also encouraged by Roger Ulrich’s study in 1984 which revealed the positive
impact of greenery of health and wellbeing, and consequently highlighted that a shortage of this in cities
may be detrimental to psychological health.21
System trends – extensive direct > intensive hydroponic
“Ivy and ruins go together in the imagination like strawberries and cream”.22
Fear and hesitation surrounding the biodeteriorative nature of plants on walls resulted in many buildings
being stripped of their traditional ivy. Scepticism is not entirely unfounded as many associate it with the
romantic images of the ruinous buildings taken over by plants, however studies have proven that in the
case of these traditional direct applications, ivy will only penetrate building structure where there are
cracks or soft mortar. 23 The University of Oxford in 2010 investigated the potential harm of Hedera
Helix (ivy) on limestone and noted that on removal the limestone was undamaged and in face the aerial
rootlets in fact cleaned the stone of soiling, with little to no trace of attachment.24 With the correct
information on the nature of the plant and the outer wall material, many problems can be easily evaded.
Scepticism is also derived from poor media reception and so many think of facade greening as
“outlandish and difficult to accept”25 reinforced with the creations of high profile designers, such as those
of French Botanist Patrick Blanc, which appear insincere attempts at sustainable systems and are more
artistic statements, with little sustenance.
There is also a strong tendency in the UK to be quite reserved, especially with regard to conservation of
heritage, which precludes an opinion that the introduction of green facades would be detrimental to the
heritage stock and image of the city. There is a need also for people to overcome their “cultural
inhibitions”26 of the integration of buildings and vegetation and realise their potential, but not be unaware
of the issues of maintenance and initial cost, which for the time being remain high for living wall systems,
but can be more reasonable with the traditional systems.
There is scope for the architectural profession to aid in this increased awareness by first approaching the
large corporations and institutions which have a considerable influence over public opinion (e.g. schools,
transport systems and hospitals) and in doing so cost and maintenance27 is more manageable, until prices
are brought down through more extensive use. Concurrently the profession can look into greater means
of integration of these systems into their designs as not merely a retrofit or “veneer of green respectability”
but rooted much deeper in the understanding of generating a sustainable society.
20
P.30 The Ecological Facades, Urban Geographer, Matthew Gandy.
Environmental Psychology: An Introduction pp. 50
22
Dunnett, N., Kingsbury, N., Planting Green Roofs and Living Walls, Timber Press, London 2008 pp. 231
23
Dunnett, N., Kingsbury, N., Planting Green Roofs and Living Walls, Timber Press, London 2008 pp. 230
24
English Heritage Ivy doc / 33
25
Dunnett, N., Kingsbury, N., Planting Green Roofs and Living Walls, Timber Press, London 2008 PAGE NO.
26
Dunnett, N., Kingsbury, N., Planting Green Roofs and Living Walls, Timber Press, London 2008 pp. 192
27
MENTION COST AND MAINTENANCE
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