Detail 12/2008 pp 1454
Positive benefits:
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Rainwater retention after heavy precipitation
Microclimate improvement
Reduce local heat gains in cities (heat island effect)
Energy saving from vegetation as a screen for the building against wind
Evaporative cooling
Noise / traffic sound absorption
Air quality improvement
Avoid space for graffiti
Visual upgrade to buildings
Biodiversity – BUT issues with insects and mice?
But:
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Artificial watering required for green facades unlike with green roofs
Context:
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Cold windy regions – cultivation of trees, hedges in front of walls for protection
Mediterranean climates – “planted facades form part of natural system of climate control
for buildings since antiquity”
Buildings + vegetation = symbol of “building in harmony with nature and of architectural design
subordinating itself to the natural environment.”
“Garden City Movement late 19th cent. Seen as the first ecological reaction to industrialisation”
Planted facades more popular in America, Asia Australia than in Europe due to the problems with
heat that their climates pose.
“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.”
Plants that grow up from the ground have a limited height – beyond this containers can be
distributed up the wall (homogenous infill may take several years)
“rear ventilated systems” – vertical garden, living wall, plant wall and wonderwall – examples of
planting beds vertically. – modular and hydroponic systems.
“Green vertical systems can be differentiated as extensive and intensive systems. Extensive systems
are easy to build and have minimum future maintenance, and intensive systems have more complex
implantation and require a high level of subsequent maintenance”
pp. 1457
Patrick Blanc - Hydroponic Wall
Traditional methods have their disadvantages - earth soaked in water as a substrate layer functions
in plant containers or in the ground however this poses problems due to the sheer weight and
constructional depth required make construction / suspension difficult
Patrick blanc discovered however that it the roots Are covered in soils with adequate enrichment of
nutrients that plants can grow vertically. Hydroponic cultivation – WITHOUT SOIL. Demands on the
substrate are much more complex – even with computer programming – difficult in unpredictable
weather conditions to monitor the requirements of the plants.
SUBSTRATE = “the layer that provides the roots of plants with mechanical support, that ensures the
supply of nutrients and that stores and drains off moisture.” Liquid containing additional nutrient
solutions fed horizontally at regular intervals sprinkles substrate with “droplet system”
Considerations:
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Even moisture distribution
Scope for moisture retention
UV radiation resistance
Rot resistance
Adequate strength for fixing the plants
Attractive appearance during the growing phase
ROCK WOOL after trials aborted as material becomes “unevenly compacted and some areas then
absorb too much moisture”
1. Modular Façade with Soil Substrate in Polyethylene Containers, Eco-Shop, London – LIVING
WALL www.eltlivingwalls.com
modular grid of high density polyethylene (HDPE), resistant to UV radiation, 500*500 size,
depth 64mm. water droplet system with small retention in each hollow for hot periods.
Ferns/tropical plants should be sprayed in addition to the irrigation system.
2. Modular façade planted with Sedum in Stainless Steel containers. Citi-Data Centre, Frankfurt,
ttsp + HWP + Seidel architects (largest area executed on Frankfurt bank – 750 m2)
Interest in the modernism of Stanley Hart White has been renewed by the discovery of his 1938 patent for the
first–known vertical garden. White's patent for the Vegetation-Bearing Architectonic Structure and
System describes a new method "for producing an architectonic structure of any buildable size, shape or height,
whose visible or exposed surfaces may present a permanently growing covering of vegetation." In six beautifully
illustrated pages, White describes the technology and art of this invention, and in the process, defines a new
garden typology not fully realized until after his death. Even with the prominence of vegetated architecture in
contemporary discourse, White's invention remains unrealized and entirely unknown more than eighty years after
its initial conceptualization. In his 1931 writings on the subject of What is Modern, White outlines the art of
creating vertical gardens of steel, substrate, vegetation, light, and sculpture to act as backdrops to modern ways
of thinking and the pageantry of modern living. This project reveals the techno–historical origins of the vertical–
garden type, and materializes the undocumented intricacies of vegetation-bearing architecture in a time when no
such history exists.
Effectiveness of Green Infrastructure for improvement of air quality in urban street canyons
pp. 7692
“deposition rates [of particulate matter] to vegetation are much higher than those to hard, built
surfaces”.
Consider “deposition as a pollution control measure” as opposed to reducing air quality rates. Air
pollutants continually exceed public health standards, also noted that there is no safe threshold, esp
for PM exposure – continually endeavour to drive down concentrations.
“the nature of the surface and is generally higher to vegetation than to other urban surfaces because
of the metabolic uptake by the plan, the “stickiness” of the leaf surface, the large surface area of
plants, and the aerodynamic properties.”
Previous studies concluded little difference to city environments by urban vegetation. E.g. Chicago
<1% on current vegetation cover
Pp . 7693 Simply increasing the greenery in street canyons will undoubtedly fail, as “air recirculation
and the spatial distribution of emission sources” must also be considered.
Results pp. 7695
Green walls across large areas of street canyons NO2 and PM – as much as 15 and 23% - strongly
dependant on wind speed and canyon geometry (residence time) but not on the initial pollutant
concentration. Should make “important difference to pollutant transport and regional
photochemistry”.
“Greening of in-canyon surfaces is more effective thgan greening roofs … because it acts directly
upon the relatively small volume of air in the canyon, rather than indirectly via the UBL.
Pp. 7696 noted potential with low wind speed for “considerable potential for reductions in the
frequency of exceedence of air quality limit values,” - NO2 and PM ~40% and ~60%
Green Design: Ágnes Novák
pp. 39 Micro climate
continuous solid surface4 lead to overheating of the micro climate in cities. Rising air dust particles
include precipitation.
Air polluting materials:
-solid: dust, soot, ash
- liquid: vapour from chemical reaction of gases or condensation
- gas
-solid liquid: smoke
pp. 42
“never in the history was man separated so drastically from the nature by the constructed
environment.”
Pp. 43
“The averga4e oxygen production of leaves in 12 hours of light a day is some 4 litres per m2 of leaf
surface. One man consumes approx. 175g of oxygen annually that is about 335l a day.” But cities’
issue is not lack of oxygen, but rather the high concentration of pollutants.
pp. 45
green plants on walls – reduce velocity of rising air flow and so polluting elements will stick to the
leaves.
Approx.. 10% of solar radiation is reflected by leaves, about 70% absorbed, 20% passes through to
surfaces.
pp. 47-48 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.
Sound insulation “leaves have a noise reflecting and noise absorbing character. Leaves- having a
laminated structure – absorb and transfer – so reduce – part of the acoustic energy and reflect a
further part of it.”
rustle of leaves suppresses other sounds. – “masking”.
“Investigations resulted a noise reduction value of around 5 dB.”
pp. 53 – evergreens on N facing walls on account of their insulation potential
CBA for green facades and living wall systems
pp. 110
Green facade – climbers directly to the building surface –as traditional – or supported by trellis or
cables. Indirect greening – cables or meshes, (such as steel, coated steel as, galvanised steel) wood,
plastic or aluminium. Nutrients and watering system if rooting space insufficient – in this case, the
system is defined as a LIVING WALL SYSTEM
Living wall system(LWS) aka green walls, vertical gardens, constructed through the use of modular
panels, ea of which contains its OWN SOIL OR ARTIFICAL GROWING MEDIUMS e.g. foam, felt, perlite,
and mineral wool, based on hydroponic culture, using balanced nutrient solutions to provide to the
whole or part of the plant food and water req.
pp. 111 / 1.3
variety of options for vertical green envelopes .
simple climbing plants at base of facade (DIRECT GREENING SYSTEM) €30-45/m2
INDIRECT (plants + supporting material) 40-75€
plant boxes combined – costs vary acc to the material (from 100-150€ for plastic, up to 800€ /m2 fpr
zinc coated metal).pre-vegetated panels costs vary from 400-1200€ dep. On facade surface, height,
location, connections . => LWS much more expensive than green facades purely on account of the
watering and nutrient maintencance req., materials involved and design complexity. But LWS
increase the variety of plans engages as not exlusive climbing plants - MORE CREATIVE AND
AESTHETIC POTENTIAL.
Benefits of VGS
Personal/social benefits:
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Extra stagnant air layer insulating effect, “REDUCES THE ENERGY DEMAND FOR AIRCONDITIONING UP TO 40-60% IN MEDITERRANEAN CLIMTE”.
Green wall increases property value as much as “good tree cover” might.
Environmental benefits: pp. 112
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Acoustic- very thin coverage has little benefit
UHI reduce US energy consumption for air con 20 % $108 billion energy use saving
Biodiversity – köhler- Berlin – attraction of insects and birds
Dust mitigation- streets with trees only 10-15%of total dust particles. “gaseous pollutants
can be dissolved or sequestrated though stomata on plants and leaves”
Maintenance costs depend on:
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The type of greening system:
o Direct/indirect at ground level only concern PRUNING ANNUALLY, costs differ after
the 5th year on account of the different growth rates
o Indirect with planter boxers maintenance also includes water pipes and plant
species substitution
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Modular panel system – consideration also for the replacement of the panels, plant
species substitution.
Disposal include removal of the plants and structures, transport to landfill, and dump taxes, and the
renewal of cladding.
Real-estate value:
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Semi central – 3.0%
Central - 2.0%
Periphery – 5.0%
Energy saving
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e.g. 300mm concrete, external 150mm polystyrene insu energy saving for cooling 1.4 – 2.6%
internal insulation 4.7 – 6.2%; 400mm concrete and no insulation 65.8%.
thermal resistance assumed 0.09km2 W-1 stagnant air layer behind the foliage.
Longevity
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reduces maintenance to façade to which the green wall is attached – protective action,
shading effect. Vertical greening protects against:
o UV rays, temp changes, acid rain, ice and pollution; reducing the deterioration.
Plaster replacement typically 25-35 years, green wall will increase this to 50 years, as with
the replacement of the green wall.
Social benefits:
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Air quality improvement – in this case assumed to be half of what “currie and bass” estimate
for green ro9ofs which is 75-85 kg pollutants for 1ha green roof.
Pp. 117-8 Habitat/biodiversity – the green wall can encourage micro-organisms as well as
larger species such as insects, bees and bird. However this is not a strongly considered city
incentive with green wall implementation and so results are largely qualitative and there is
little quantitative research.
UHI – vegetated surfaces have different “albedo value” to hard surfaces (20-30% for
vegetation / 5% for asphalt). “The positive effect of vegetation in reducing the urban heat
island phenomenon is evident only if a large surface of the same area is greened (e.g. parks,
gardens, many green facades or roofs).
Results and discussion:
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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.
Best benefits for all greenery systems are the summer air con qualities and the increase in
rental income, both around 1000€/ yr.
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DIRECT GREEN FAÇADE PBP 20years
Indirect - HDPE better than steel mesh – for the former PBP 16 years