A truly green roof is a roof of a building or a home that is partially or completely covered with vegitation and a growing medium, planted over a waterproof membrane. These types green roofs are also referred to as "living roofs". A green roof can also mean a roof that is utilizing some type of "green" technology, such as solar panels.
What are we talking about is associated with green building, but simply one aspect of this practice. Green roofing, like green building is centuries old, and simply means that you cover your roof with plants, usually turf, but some of the most attractive green roofs are sown with grass and wildflowers and in the summer smell like water meadows.
The idea of green roofing is thought to have evolved in Scandinavia and to have been developed by those clever people the Danes back when a lounge suit was made our of Elk hide. Green roofs have been a part of life overseas in Europe and Asia for many years, similar to sod or garden roofs. Composed of earth and living plants, a green roof provides a cooler roof during the summer months than a traditional roof, thereby reducing the energy required for cooling. Additionally, the earthen roof will soak up precipitation, thereby reducing the quantity of rainfall going into storm sewers or streets. And no, a “green roof” is not always green – due to changes of season, green roofs may appear red, orange, yellow and all colors in between at different times of the year.
Turf was used to cover the roof and keep the home not only dry all of the year round but warm in the winter and cool in the summer. Green roofing is a wonderful way to enhance the look of your home, office or place of work and to help the environment. The human species seems to have a symbiotic relationship with plants, as they have particular use for the carbon dioxide we exhale and we thrive and rely on the oxygen that they expire. In summary, that means that a green roof is an excellent way to help the human race, offer plants somewhere to live and clean the up the environment all in one place.
One specific type of green roof you could choose is called a "biomass roofing system." A biomass roofing system is one of the new buzz phrases from the green building community, but is actually known in a large number of places around the world by another name - a "thatched roof." Thatched roofs have always been used to cover the tops of buildings and keep out the rain and basically they do a very good job, although it has to be said that building insurers tend not to like them too much because in their opinion they represent a heightened fire risk. Another negative is that the art, trade or craft of thatching has in a lot of areas become very exclusive and that is because there are only a few practitioners available and the cost may be prohibitive for many, although they may last for 50 years or more.
There are other forms of "biomass roofing" and they take the form of using natural materials to 'tile' a roof, wood tiles for example are a very popular roofing material in some parts of the USA, France and Germany. For more examples of some green roof projects in the United States, read this blog post.