Since the days of Babylon, vegetation has been growing on, in or around both the horizontal and vertical planes of buildings, more specifically the roofs and walls. The most recent green trends have been including a variety of what the industry is calling “Green Walls, Living Walls, and Vegetated Façades,” and we have heard manymore names, too. The green roof movement has naturally evolved to green walls - no pun intended, but the green roof has now climbed over the parapet and down, or up the walls. Designers, architects and engineers now have the possibility of encasing a building in some type of live vegetation whether for aesthetics, function or notoriety.
A green roof is a roof of a building that ispartially or completely covered with vegetation and soil, or a growing medium, planted over a waterproofing membrane. This does not refer to roofs which are merely colored green, as with green shingles. It may also include additional layers such as a root barrier and drainage and irrigation systems. Container gardens on roofs, where plants are maintained in pots, are not generally considered to be truegreen roofs, although this is an area of debate. The term "green roof" may also be used to indicate roofs that utilize some form of "green" technology, such as solar panels or a photo voltaic module. Green roofs are also referred to as eco-roofs, vegetated roofs, living roofs, and greenroofs.
Green roofs are used to:
← Provide amenity space for building users — in effect replacing a yardor patio Grow fruits, vegetables, and flowers
← Reduce heating (by adding mass and thermal resistance value) and cooling (by evaporate cooling) loads on a building — especially if it is glassed in so as to act as a terrarium and passive solar heat reservoir
← Reduce the urban heat island effect
← Increase roof life span
← Reduce storm water run off — see water wise gardening← Filter pollutants and CO2out of the air — see living wall
← Filter pollutants and heavy metals out of rainwater
← Increase wildlife habitat in built-up areas — see urban wilderness
A green roof is often a key component of an autonomous building.
According toGreen roofs for healthy cities:
"In North America, the benefits of green roof technologies are poorly understood andthe market remains immature, despite the efforts of several industry leaders. In Europe however, these technologies have become very well established."
A 2005 study by Brad Bass of the University of tToronto showed that green roofs can also reduce heat loss and energy consumption in winter conditions.
Modern green roofs, which are made of a system of manufactured layers deliberately placed overroofs to support growing medium and vegetation, are a relatively new phenomenon. They were developed in Germany in the 1960s, and have since spread to many countries. Today, it is estimated that about 10% of all German roofs have been “greened.” Green roofs are also becoming increasingly popular in the United States, although they are not as common as in Europe.
Many green roofs are installedto comply with local regulations and government fees, often regarding stormwater runoff management. In areas with combined sewer-stormwater systems, heavy storms can overload the wastewater system and cause it to flood, dumping raw sewage into the local waterways. Green roofs decrease the total amount of runoff and slow the rate of runoff from the roof. It has been found that they can retain upto 75% of rainwater, gradually releasing it back into the atmosphere via condensation and transpiration, while retaining pollutants in their soil. Elevation 314, a new development in Washington D.C., uses green roofs to filter and store some of its stormwater on site, avoiding the need for expensive underground sand filters to meet D.C. Department of Health stormwater regulations.