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Search forLiving roofs bring a piece of the country to the city's skyline
Monday, August 04, 2008, 12:53
These roofs were used by the Vikings hundreds of years ago, and, with a modern twist, they are now a popular, sustainable, and aesthetic building practice.
City architect Tony Pollintine has several years' experience working with green roofs.
Last year he designed one for the combined universities campus building in Tremough, Cornwall.
Closer to home, Tony's projects include a green roof at Pinhoe Primary School and another at St Nicholas Catholic Primary School, in Ringswell Avenue, Exeter.
In Exeter, he has three residential green roof projects in the pipeline.
Tony works at Grainge Architects, in Baring Crescent, Exeter, and is a great advocate of the technology. He says the roofs offer lots of environmental advantages and are an educational resource for schools.
“What was nice about doing the schools was that we were giving the children a slice of the Devon hillsides and meadows right on their doorstep,” said Tony.
“For the Pinhoe building, we put logs and stones on the roof for insects to crawl around in and for birds to perch on. That part of the roof is level with the ground, so the children can see what's happening.”
In terms of the environment, green roofs can be hugely beneficial to an area.
“With these roofs you are actually promoting the local ecology and recreating habitats that might otherwise have been lost.” said Tony. “You are offsetting the loss of green space by lifting the green area up off the ground.
“We like the idea of indigenous stocking and planting, which is why we use wild flowers.
“We work with experts to survey the area and identify what the local species of flora are.
“The roofs create a habitat, and with that comes insects, bees, butterflies and birds. It's self-perpetuating.”
Flooding is a major problem in most urban areas, partly due to overdevelopment.
But green roofs can help or even offset excess drainage because they soak up rain water.
“Rather than surcharging the drainage system, the roofs hold the water, letting it slowly evaporate into the air,” said Tony.
“If there is a massive storm the water will of course eventually flow into the drainage system, but it will do so at a slower rate.
“If everybody in the country who had an extension were to have a green roof, we would see a huge improvement.”
There are two types of green roofs: intensive and extensive.
The former variety is much thicker, requiring strong structural support, and is not commonly used.
Extensive roofs, on the other hand, are the kind Tony is promoting.
“These roofs are quite thin,” he said. “In simple terms they consist of a waterproof membrane, protective foam and planting aggregate.
“The aggregate is a specially controlled low-fertility mix, so it will only support particular species.”
By using this type of subsoil, only the hardiest plants survive, and these are the wild flowers that grow on the hills and cliff tops.
“The flowers are self-regulating perennials, so they look after themselves and come back every year. And that means there are no maintenance issues!” said Tony.
Another advantage of green roofs is that they are extraordinarily good at insulating and protecting.
“Green roofs shield the internal roof from the elements and lengthen the life of the build beneath,” said Tony.
“And one of the other biggest advantages is that visually, they are very nice to look at! If you're doing a housing extension, it's much nicer to look out of your window and see a nice green garden, rather than a flat black roof.
“And in terms of planning permission, green roofs can unlock a site where development might not have been possible.
“That's because these roofs have green credentials, and because you can make the building disappear into the landscape.”
At Grainge Architects, Tony says he and his colleagues will be pushing green roofs even more in the years to come.
“Our practice is very green. We design on the basis of understanding natural physics, and use lots of daylight, natural ventilation and avoid mechanical systems,” he said.
“Doing things naturally is the ethos of the practice. Green roofs have grown in popularity over the last three years, and we will definitely be doing more of them in the future. It is often hard to persuade commercial developers to put them in, but with utility bills rising, and environmental awareness increasing, I think more people will start thinking about greener alternatives.
“If everyone had these roofs we could change the microclimate of an entire town.
“That has already happened in Stuttgart, in southern Germany, where green roofs have become a little habitat in the centre of the city.
“These roofs cross the boundary between architecture and landscape. It's a linking together of the two disciplines and gives the building a bit more warmth. Green roofs have so many advantages. When you finish a project you get a sense of wonder when the flowers suddenly spring into a lovely meadow. It's a wonderful thing to give to people.”
Top and above, views of the green roof on the new St Nicholas Catholic Primary School in Exeter, designed by architect Tony Pollintine
