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As if the implications of the unfolding global financial crisis weren’t bad enough, the Irish economy must also contend with the consequences of a banking system exposed to unprecedented property-related debts. Reflecting on the ongoing crisis, Richard Douthwaite explains why investment in local energy innovation may prove the key to improving Ireland’s economic health
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The green roof on law firm Allen & Overy's London headquarters
McEntee says that green roofs can have a positive effect on local water
quality too. In Dublin, roof drainage systems carry water directly into
the sewage network. When the sewers fill during heavy rainfall, diluted
raw sewage flows into the Liffey. Because green roofs absorb so much
rainfall, they ease pressure on sewage systems and reduce overflow into
local rivers.
Intuitively, green roofs can boost biodiversity in urban areas.
Environmental consultant Dusty Gedge says that his interest in green
roofs developed from his work on bird conservation in London. “I was
working on the conservation of the black redstart, and I thought, why
don’t they just put the habitat on the roof?” says Gedge, who estimates
that between existing green roofs and planned future ones, there will
soon be 700,000 square metres of green roof in London.
With a background in biodiversity, Gedge isn’t a fan of homogenous
sedum mats. “The construction industry is very mechanistic. It likes
everything to be the same, whether it’s paving or bricks…a green roof
is essentially a landscape. If you’re building a green roof near the
Burren, the Burren should essentially be the green roof at land level.”
Mairead Stack says that Dublin City Council is also examining the concept of biodiverse roofs, on which a material such as gravel or concrete is laid at varying heights to create a diverse topography that replicates brownfield sites. “Brownfield sites have one of the highest biodiversities. You get a whole lot of very rare plant and insect species,” she says.
Green roofs are compatible with other sustainable rooftop technologies, such as solar thermal arrays and rainwater harvesting systems, and green roofs can even improve the performance of solar photovoltaic (PV) systems: by reducing localised temperatures they prevent PV panels from overheating, an often-cited reason for inefficiencies in PV technology.
Clearly green roofs boast an impressive list of benefits, but are they cost effective? While additional materials and labour can add up to 30 per cent to the cost compared to a conventional roof, this can be offset by savings from reduced energy consumption and roof maintenance. By sheltering roof materials from the weather, green roofs can double or even treble their lifespan, according to research from Penn State University.
Dusty Gedge believes that attitudes towards green roofs are changing: “Six years ago nobody talked about climate change, and now people are interested in the urban heat island effect, energy performance, storm water attenuation and growing food on green roofs,” he says.
While green roofs are growing in popularity, their vertical equivalent
has some catching up to do. Perhaps the most famous green walls are
those gracing Parisian streetscapes, designed by French botanist
Patrick Blanc. In Paris, subsidies are available for residents to
install green walls on building facades. The city authorities even look
after maintenance. “They don’t have any more places to green on the
ground, so they’re going up the walls,” van Lennep says.
Outdoors, there are two types of green wall. Common green facades are
facilitated with simple trellising. In other cases, vegetation is
rooted in soil or an inorganic growing medium, often in pre-vegetated
panels that are installed over the building structure. “These are
highly engineered systems,” van Lennep says.
Like green roofs, green walls offer practical benefits: they create a
dead air space that provides thermal insulation, cut down daily
temperature fluctuations at the wall surface by up to 30oc, and reduce
wind chill by up to 75 per cent (with a knock-on reduction in heating
demand of up to 25 per cent). They also remove pollutants from the air,
help to counter the urban heat island effect and sequester carbon.
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Issue 2, Vol 5 Out Now
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