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What is a Green Roof?

A green roof is covered either partially or completely by living plants and some kind of substrate in which the roots will anchor themselves. This is actually not an altogether new idea, although it has gathered a great deal of momentum over the last few years. Traditional pioneer homes across the Canadian prairies were topped with sod – a layer of growing grass and dirt – as insulation. Why the growing green roof trend now? It’s a way for homeowners and even business owners to create a little piece of relaxing, environmentally-friendly green living space.

Green Roofs as Insulation

Just as it did 100 years ago, sod lining on a roof can indeed provide a good deal of natural insulation. The thick layer of grass and soil not only absorbs excess water from rain or light snow, but it traps heat below the roof level to make a home or office more comfortable. Of course, one can’t simply strip a layer of sod from the ground and place it on the roof; there is a process that should be followed.

Firstly, not every roof is a suitable for a layered garden. Flat roofs are much easier to work with, although lightly-pitched roofs have successfully been turned into green spaces. When deciding to turn a flat roof into a green space, it is essential that you ascertain whether or not the roof has been properly waterproofed. If not, water from the irrigation system will eventually pool and cause leaks or sagging in the roof. If well-planned, on the other hand, a sod-based roof garden should need very little maintenance.

Rooftop Container Gardens

Another option for installing a green roof is to use containers, such as large and small self-contained plant pots. This way, it isn’t absolutely necessary to have a well-waterproofed roof, as any rainfall will be funnelled out the roof’s drainage system. The roof itself will stay the same, and the plants will anchor themselves in their individual pots. It is important that your chosen plant pots and containers be heavy, so that they won’t be knocked over by strong winds, rain or hail. A container garden needs more focused maintenance than an irrigated sod garden, especially if rainfall is unreliable in your area. You may need to visit it regularly to provide extra water or remove puddles in the pots – but then, what’s the point of a rooftop garden if you don’t want to visit all the time?

Green Roof Ponds and Greywater Treatment

Greywater is water that has been used, but is not classified as sewage. For example, dishwater and laundry drainage are both types of greywater, both of which can be treated in a specialized roof pond. Such a pond is used to collect various types of greywater and filter it through the natural processes of grass and other plants. It’s a basic recycling strategy that many people are starting to use at home and in the work place. To make this work, the roof should be metal-based and well waterproofed – obviously!

There are plenty of options to consider when putting together your own green roof. You can make it as simple or complex as you like: a lush, beautiful garden in which to spend an afternoon, or a hard-working, greywater recycling rooftop pond with complimentary solar panels. A great green roof might take some time to design and build, but the outcome is worth it.

Photo from Wikimedia.