If you're a fan of the fascinating TV show, Grand Designs, you'll be no stranger to the concept of 'green roofs'. The program frequently shows off magnificent homes that have incorporated this eco-friendly system into their design, either by choice or to meet planning requirements in conservation areas.
The concept isn't new, of course. The history of green roofs stretches back thousands of years, probably starting with the turf roofs of Viking dwellings in Scandinavia. Although, perhaps, the choice there was more to do with what building materials were available.
Modern green roofs - and walls - are building elements designed to support living vegetation in order to improve a building’s performance. And for that reason, they are also known as ‘living’ roofs and walls.
At first glance, covering a roof with living plants, that require water, would seem like a strange concept, and one guaranteed to result in leaks and structural damage! But that's far from the truth.
Green roofs for all
A green roof is a roof surface, flat or pitched, that is prepared by applying a waterproof membrane, on top of which a growing medium and vegetation is added. These are generally classed as 'extensive’ - a thin growing medium (up to 200mm deep) with ‘groundcover’ vegetation - or ‘intensive’ - soil over 200mm deep supporting vegetation up to the size of trees.
Green walls can be external or internal, and are basically walls that support a cover of vegetation, rooted either in stacked pots or growing mats.
Green roofs are used quite extensively in modern building in Europe. Indeed, some city and national governments insist on their use. For example, in Linz, in Austria, all new residential and commercial buildings with rooftops larger than 100sqm must have green roofs.
The concept is still relatively new in Australia, but it is starting to take hold and Brisbane City Council has included green roofs in its proposed action plan for dealing with climate change.
Many benefits to be had
The major difference between those Viking constructions and modern green roofs, is technology. The surge of interest in - and the need for more sustainable development has sparked new technologies that make green roof construction easier and more economical.
Once you get your head around the idea of trees growing on top of your home, there are many benefits to be had. For example, in cities, green roofs are often seen as an oasis amongst the mountains of concrete, brick and steel.
In these dense urban environments, they compensate for the loss of useful landscaping at ground level, providing an opportunity for occupants to grow their own food.
Visually more inspiring than traditional roofs, they also tend to make buildings more environmentally friendly, and can even be used to treat wastewater.
Some of the many benefits include a longer roof lifespan; reduced heating and cooling requirements; soundproofing; reduced storm water run-off; cleaner air; increased biodiversity and, of course, that feel-good factor and reduced stress for the occupants below.
If you think about it, planting window boxes or balcony containers, and growing vines up our walls is just the start, but shows mankind's desire, or even need, to surround itself with greenery, and to grow food. Green roofs and walls simply take this to the next stage.
Green walls are very easy to establish, and most garden centres and major hardware stores sell complete systems, that are easy to erect and use.
Green roofs are harder, of course, and generally require some expert help and advice to establish. Luckily, Australia has an organisation set-up specifically to do that! Find out more by contacting www.greenroofsaustralasia.com.au