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Green Roofs

One aspect of green architecture is Green roofs or rooftop gardens. It can incorporate the use of green materials, such as recycled goods, sustainable resources, or materials that impact our home Earth less during production. Green architecture is only as green as the engineer envisions - she can incorporate sustainable ingredients (as an example to others as well) or go the easy route and use readily available en-masse materials which we can presently afford, but that will ultimately create an unfortunate circumstance for the world at large. Green roofing is done by creating permeable and impermeable layers on a relatively flat roof (although not always). Plants are integrated onto this series of layers on the roof. And up, into the blue. The Green roof technology has been around for hundreds of years in Europe, and there are beautiful examples of it from all over Earth. We are beginning to use it here in the USA, funded through the EPA (Environmental Protection Agency, federal and state levels) in the large-scale buildings, and on the small scale it is being done privately.

The Technology

In order for a rooftop garden to work, there are two important requirements that must be met. One, the roof must be impermeable to the inside of the building. And two, the structure of the building must be as such that the roof does not impose excess weight upon it.

Green roofs are built in layers upon buildings that can withstand the weight. The bottom layer is made of an impermeable substrate that is strong enough to withstand years of root intrusion and water impact. The next layer is a layer of substance that lets water through, but not rocks. The next layer is a very permeable layer, like rocks or something like them, that allows the water to filter through. Next, some companies put a fine layer of mesh under. This is the soil layer. And finally, the plants are planted. For more information on the composition of a green roof, visit these sites.

Social Design Notes - Green Roofs
A Green Roof Company, Zinco. Here you can easily see possible layers.

Benefits

There are a number of important benefits attributed to Green roofs:

  • Significant reduction in water runoff and pollution when compared with conventional roofs. Thus, urban stormwater runoff is lowered significantly, a problem which is pervasive throughout American cities. As seen from the sky, during the first rain of the season, a huge belch of black pollution flows down the stormdrains and into the bays. A major source of this pollution is the slick roof tops in cities that hold pollution-filled dirt -- up until the day that it rains, at which point the filth travels down the street and into our natural surroundings, creeks rivers and oceans.
  • Preserve biodiversity and natural habitat for birds and beneficial insects in an urban atmosphere
  • Protect the roof from severe weather such as UV sunrays and hail. These roofs can last over 50 years - most roofs must be reroofed every 15-30 years, and reroofing is a costly procedure.
  • Minimize water damage and maintenance costs
  • Increase water percolation back into soil rather than letting water be taken into rivers, bays and oceans where we cannot use it. Water is becoming a very precious resource, one which we are quickly depleting out of the water tables below us. Each winter it rains, but only so much returns to the water table. Be decreasing sheeting of water and allowing it to percolate back into the soil, green roofs increase the life span of our water tables. Another way of doing this in cities is through managed wetlands and water reuse. Over the last century we have done away with many of our Bay Area natural wetlands by paving over them. By carefully managing our water, we will extend the lifespans of our water tables, reducing the necessity for costly and pollutive methods of water extraction such as desalinization plants.
  • Act as a natural insulator, which reduces energy consumption and heating / cooling costs. They also absorb noise pollution and sunlight, rather than reflect them.
  • Absorb air pollution and acid rain
  • Reducing the urban heat island effect (heat waves). It has been found that large cities are on average about 10 degrees hotter than the surrounding area, which in turn affects local climate and rainfall.

Political, Economic,and Social Support

So, is anyone doing green roofing? How would one go about funding it? What companies are involved?
Luckily, there is quite a bit of support for green roofing in the world, and it is on the upward incline. There are several companies in the business, universities studying it, and people who want it to happen.
Roofmeadow.com
A German Green Roof Company

Green Roof Examples

From modern green roofs, such as the thousands in Germany and Hundertwasser's ecological building creations, to ancient green roofs such as the Hanging Gardens of Babylon (one of the Seven Wonders of the World) constructed around 500 B.C., green roofs dot our world with their magnificence. In the following list of pages you will see examples of their beauty and logic.

A Hundertwasser Building Page
A Page About Hundertwasser's Philosophy
William McDonough's Site

Finally, there is an excellent page on Green Roofs at Wikipedia for more information.

"The truth is a many-faceted gem."- Sofia Penabaz-Wiley