How does the world find shelter from the storm of climate change? What humans put over their heads is one good place to look.
In 500 B.C., a legendary green roof was regarded as one of the Seven Wonders of the Ancient World. The Hanging Gardens of Babylon were possibly constructed by King Nebuchadnezzar II as a gift to his wife, Amytis. The 75-foot tall garden featured terraces and columns laden with vegetation. A rainbow of colors and fragrances were meant to appeal to the senses of Amytis, who missed the lusher landscape of her Medea birthplace. Quite a gift, considering that the Gardens could only become a reality through a sophisticated irrigation system installed in a desert environment.
Less famous than Nebuchadnezzar’s creation are the green roofs of the past called sod roofs. Sod roofs were covered with soil and plants. For centuries in northern Scandinavia, they multi-tasked by answering housing and agricultural needs as well as being a spot for hosting ceremonies and special events. Sod roofs, reminiscent of homes for hobbits, provided insulation during cold periods and a cool place when it was hot outside.
What is a green roof?
Today, green roofs, or ‘living roofs,’ apply the wisdom of the past with the innovation and technology of the present. Moving beyond images of homes for hobbits and monumental gifts for queens, green roofs are now poised to play a vital role in addressing the pressing challenge of climate change.
What is the contemporary definition of a green roof? Green roofs grow living organisms like trees, shrubs, herbs, grasses, ferns, and mosses that typically grow in permanent sites. In addition, they help absorb water and inorganic substances, as well as synthesize nutrients. Situated on rooftops, they replace the natural landscape that disappeared when the building was constructed. These green roof structures can be immense, block-long buildings, small abodes and residences, or something in-between.
Types of green roofs
Intensive and extensive are the two most often developed green roofs.
Intensive roofs are usually applied to commercial buildings. These roofs have grasses, ground covers, flowers, shrubs, and trees. They can feature paths, walkways, ponds, fountains, benches, tables and flower boxes to prompt interaction between people and the more natural surroundings. Sometimes referred to as ‘rooftop gardens,’ they can actually become settings for dining, working and simply relaxing. Intensive roofs have more depth than extensive roofs. Their deeper soil suits larger vegetation types. Pests have a harder time intruding upon intensive roofs because of their height. Intensive roofs tend to be irrigated and continue to be aesthetically pleasing in dryer climates. However, they are more labor intensive than extensive roofs.
Benefits of Green Roofs
Green roof benefits are often put into four categories: economic, environmental, facility, and aesthetic. Numerous studies point out that green roofs can contribute to reductions in carbon emissions, temperature, rainwater run-off, urban heat island, and air pollution—while increasing biodiversity. These attributes will be of increasing value as the planet deals with the increase in heat waves, heavy rains, floods, and landslides due to climate change.
A successful green roof reflects its climate and environment. Although they represent a distinct type of urban habitat, green roofs have been treated as an engineering or horticultural challenge, rather than as ecological systems. The environmental benefits provided by green roofs derive from their functioning as ecosystems. Any successful green roof calls for upfront planning and thorough research to determine its impact for the property owner and the environment.
The Green Roof Boom
Today, green roofs have become a global movement and many regard Germany as the pioneering leader of the movement. It is estimated that green roofs cover over 500 million square feet in Germany. Specifically, 1 out of 8 of the flat roofs there are green, and the German green roof industry is growing between 10% and 15% per year.
A combination of federal and local legislation, supportive incentives, and higher taxes on run-off from conventional roofs, drives their green roof boom. How might the German experience expand throughout the world? Along with changes in policy, a wider understanding and appreciation of the benefits of green roofs is a step that needs to be taken.
There is a growing list of inspiring contemporary green roofs from around the world, that would amaze both King Nebuchadnezzar and his wife Amytis. The Autofamily residence in Poland, Meera Sky Garden House in Singapore, Olympic Sculpture Park in Seattle, the California Academy of Sciences in San Francisco, the Marchesi Antinori Chianti Classico Cellar in Italy, and the Brooklyn Botanic Garden Visitor Center can be regarded as the Seven Current Wonders of the Green Roof World.
These contemporary examples and many other green roof applications that are fortifying the movement can ignite the imagination of teams assigned to make every commercial roof a green roof in Chicago. Likewise, green roofs are a viable possibility for an individual excited about the prospect of putting a simple one on top of their single car garage. In any and all cases, extensive or intensive, the ultimate purpose of green roofs is to help put a more sustainable shelter over humanity’s head.