A HISTORY OF FLAT ROOFS
From Switzerland to the fabled hanging gardens of Babylon, humans have been growing plants on flat roofs. Because of climate issues, hot countries such as Spain have had flat roofs for century; this is the traditional design of their buildings. In hotter climates Architects used tiled flat roofs, to reflect the sun’s rays and keep internal areas cooler. Apex roofs would trap warm air and cause rooms to get too hot, whereas flat roofs have the opposite effect.
The use of flat roofs in the design of new properties has started to become more fashionable with architects and construction companies in England and they are trying to design buildings that reduce our carbon footprint and energy consumption.
In 1914-Switzerland has one of Europe’s oldest known green roofs, created at the Moos lake water-treatment plant, Wallishofen, Zürich. This roof acted to help with cooling issues.
In 1961: Berlin, Germany, Reinhard Bornkamm, a researcher at Berlin’s Free University, publishes his work on green flat roofs. It is estimated that about 10% of all German roofs have since been “greened”, or converted to green space.
Outside of Germany the City of Linz in Austria, in 1983 developers has been installing flat green roofs, as part of a continuing planning policy for the city. In the UK Construction companies have been slow in the concept of making use of flat roofs as green spaces but a number of cities have developed policies to encourage their use, notably in London and Sheffield, where buildings are now being developed with Flat roofs that have dual purpose and are energy efficient.
In 1986: at Hundertwasser Haus: Vienna, Austria, a public housing project in Vienna features trees and flowers on all the building’s roof and balconies. Residents were given a green space that would not have been available to them in the crowded town.
In 1993 Nine Houses were built in Dietikon, Switzerland, the Architect Peter Vetsch built the nine concrete residences and buried them in the earth and covered them in grass. Yet again Switzerland has been forward thinking in its building technology. The Architect has been awarded globally for the concept of producing housing that is environmental friendly, and sympathetic to its surroundings.
1997 saw Commercial Groups and Companies getting on the environmental challenge with Gap creating a 69,000-square-foot green roof on its Headquarters in San Bruno, CA
What is believed to be the world’s first green roof botanic garden was set up in a suburb of Malmo in 1999. In April 2001 The International Green Roof Institute (IGRI) opened to the public as a research station and educational facility. (It has since been renamed the Scandinavian Green Roof Institute (SGRI).
In 2000 The Church of Jesus Christ of Latter Day Saints at Salt Lake City, converted their flat roof into terraced green roof includes a three-acre meadow.
2001 saw leading Architect William McDonough and landscape architects Conservation Design Forum install the country’s first municipal green roof on Chicago’s city hall.
One of the largest expanses of extensive green roof is to be found in the USA, at Ford Motor Company‘s River Rouge Plant, Dearborn, Michigan, where 42,000 square metres (450,000 sq ft) of assembly plant roofs are covered with sedum and other plants, reducing energy costs at the plant and increasing the life span of its flat roof. Also at the same time Millennium Park Garage, Chicago’s 24.5-acre (99,000 m2) was opened; this is considered one of the largest intensive green roofs.
New York in 2003 saw the first green residential high-rise in North America, designed by Rafael Pelli with landscape architect Diana Balmori, includes two green roofs on The Solaire Project, providing an open green space that can be used for meetings and social events.
Countries and Cities around the world are beginning to convert flat roof spaces to usable green environments. In 2006 in France, a huge green roof of roughly 8,000 square metres (86,000 sq ft) has been incorporated into the new museum L’Historial de la Vendée which opened in June 2006 at Les Lucs-sur-Boulogne. Showing that green is again fashionable.
In 2008 The new California Academy of Sciences building in San Francisco‘s Golden Gate Park has a green roof installed that provides 2.5 acres (10,000 m2) of native vegetation designed as a habitat for indigenous species, including the threatened Bay checkerspot butterfly. According to the Academy’s fact sheet on the building, the building consumes 30-35% less energy, than it did before the conversion.
Economic Benefits – cost savings opportunities for the building owner include:
- It is estimated that green roofs will last up to twice as long as conventional roofs, resulting in decreased maintenance and savings in replacement costs;
- Savings on energy heating and cooling costs, depending on the size of the building, climate and type of green roof. Savings can be between 25 – 95%.
When layers of Soil and plants are used on green flat roofs, air becomes trapped between the layers. The trapped layer of air can be used to insulate for sound. Sound waves that are produced by machinery, traffic are absorbed, reflected or deflected. The ground level coverage blocks lower sound frequencies and the plants block higher frequencies, just like putting carpet in a new house reduces the noise levels.
A green roof with a 12 cm (4.7 inches) layer of ground cover, i.e. grass and soil can reduce sound by 40 decibels, where as a 20 cm (7.9 inches) layer of ground cover can reduce sound by 46-50 decibels.
- Helps reduce the amount of standard insulation used.
- Potential to reduce or eliminate roof drainage issues.
- Reduces the possibility of storm water damage.
- Increase the usable floor space of a building.
Amenity Space and Aesthetics
- Possibility of green flat roof space for meetings, and recreation;
- Aesthetic appealing could increase the sale value of the property and the marketability of the building as a whole, particularly for accessible green roofs. For example, American and British studies show that “good tree cover” adds between 6 to 15 per cent to the value of a home. Green roofs offer the same visual and environmental benefits, as well as the economic savings offered to households with green flat roofs.
- Satisfying the aesthetic needs of people looking down upon the roof from adjacent buildings can reduce some of the planning issues on new builds.
- The Fairmount Waterfront Hotel in Vancouver green flat roof is used to grow herbs, flowers, and vegetables, saving its kitchen an estimated $30,000 a year in food costs alone.
Although the initial costs of installing a green flat roof could be greater than a conventional roof system, the long-term benefits and the energy savings far outweigh the original investment. By increasing the life span of the roof and savings on energy expenditures.