A Green Roof Over my Head
by Mike Crowl on Aug 23, 2007 with 0 Comments
Leave a roof alone, and eventually something will grow on it: grass is one of the commoner occupants of the space. Having grass on the roof has been something human beings have been dealing with since Old Testament times, if Psalm 129 is anything to go by. But now the Government in the UK is encouraging people to grow grass on the roof.
How are they built?
Green roofs are built using a waterproof membrame. This is then covered by a thin layer of soil. In this soil house or building owners can then plant grasses, flowers and even vegetables. In some cases, where the structure is designed to allow for it, complete gardens can be built, merging into the aesthetics of the overall building.
- Roofs planted with grass, mosses, herbaceous borders and even shrubs and trees help absorb carbon dioxide.
- Green roofs, as they’re often called, will insulate the house or building they cover, and thus prevent some heat and energy loss.
- For inner city dwellers, such roofs are a valuable space to plant a small garden, or have a lawn.
- The roofs will absorb rain water, filter pollutants from the air, and provide a habitat for small wildlife, especially birds.
What issues are there?
Of course there are issues with having a garden above your head. The drainage design must offer both the best growing conditions for grass or plants, and also manage heavy rainfall without sustaining damage due to erosion or ponding of water. Plants must be able to feed from the soil without all the water being drained away. And of course the rest of the building must be protected in such a way as to minimise any damage from the additional weight of soil, plants and water.
Obviously a roof that is built normally is unlikely to cope with the additional weight of a garden.
Materials used.
In Germany, where green roofs have been in existence for some twenty years, various materials have been used to prevent damage to the structure: (PVC), thermal polyolefin, EPDM rubber, polymer modified bituminous sheet membranes (e.g., SBS membrane), liquid-applied rubberized-asphalt, and coal tar pitch. Of these, polymer modified bituminous membranes and PVCs are the most common. Many have been installed for over thirty years without problems.
Other materials are likely to enter the industry as their suitability is proven in certification testing and prototype installations.
A worldwide movement
Germany is not the only country to have built green roofs. In the USA there are an increasing number of projects designed which enable green roofs, in areas such as New England, Mid-Atlantic, Gulf Coast, Midwest, Pacific Northwest, and Southern California.
Australia’s government and its opposition are both enthusiastically behind the concept of green roofs.
New Zealand’s largest city, Auckland, has at present only one green roof, but a Maori PhD student, Emily Voyde, is embarking on a 3-year study to find the most suitable plants and substrates to use in green roofs in Auckland City.
Green roofs will not solve all our climate problems, especially as there are so few in existence at this point. But it is one step among many to improve the situation, and now is the ideal time to take up the idea.
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Published in: Home Improvement
