Greenroof architecture takes heat off the city where few trees grow

A children’s municipal day-care center in the western Athens district of Rendi is the site of a pilot program to introduce greenroof architecture into the concrete jungle that is Athens, particularly western Athens. Despite the area’s reputation as one of the city’s more «disadvantaged» areas, Rendi’s municipal council has a reputation for its interest in environmental issues. It decided to join forces with GreenHellas, a company that has adapted a system widespread in northern European countries as a means of slowing down the rate of rainfall runoff, to see how the system could be adapted to local conditions. The roof terrace of its day-care center is being used to test a system, adapted by a Swiss environmental expert who studied the conditions in Athens, as a way of providing more oxygen, absorbing carbon dioxide, cooling the summer atmosphere by reducing the «heat island effect» of cities, and equally important, reducing the building’s energy needs in summer. «In countries like Germany, they have plenty of greenery in their cities, so these roofs are used chiefly to delay rainfall runoff from roofs, and only secondly for other environmental purposes,» said Yiannis Mavroidis, who is general manager and co-owner of GreenHellas with his daughter, the architect Katerina Mavroidi, who is its business development manager. «Here in Athens, however, there are very few open spaces left and one of them is the roof,» Mavroidis told Kathimerini English Edition this week. «We didn’t want to reproduce the German model here. In Athens, we have different priorities – we are more concerned about increasing the amount of oxygen than drainage, although this is also important in heavy downpours,» he said. The challenge in Athens, where water supplies are a problem, was to adapt the system to plants that do not need much moisture. «The main differences with our system is the choice of plants and the need to take water shortage into consideration,» said Mavroidis. For the pilot study, agronomist Kostas Lionoudakis, who is the company’s marketing and sales manager, said they chose 13 species of ground cover and aromatic plants, including Dimorphotheca, Verbena, the succulent Lampranthus, species of lavender, Santolina and geranium. Planted in the fall, they are all doing well, but the real test will be to see how they survive the summer. At the moment, they are receiving only rainwater, but an irrigation system is in place to boost their intake when necessary in summer. The soil mix and gravel paths are laid over a layer of hydrophyllic stonewool, on top of insulating material and a waterproof membrane. Mavroidis says the material is light enough to be borne by most terraces, and not expensive to install, in contrast to the roof gardens such as those on top of hotels which require considerably more expense, more water and specially constructed roofs to bear the weight of the amount of soil required for larger plants and trees. Initial findings from a study just completed by the physics faculty at Athens University indicate that energy needs in summer could be reduced by as much as 30-40 percent with the greenroof. «We are also interested in plant conservation, and one way of doing that in Athens is to keep these plants alive on our roofs. And the model does not preclude the use of the roof for living space,» said Mavroidis. «The idea was inspired by Le Corbusier, who said that you have to return to the earth what you have taken away from it. We want to have an impact on the environment and hope to convince the authorities to appreciate these efforts. We also want to encourage efforts by individuals, perhaps through tax incentives, in the same way the use of solar water heaters was encouraged,» said Mavroidis. GreenHellas greenroofs, 4 Botsari, Holargos, 155.62, tel 210.656.4146, e-mail: [email protected], website: Greenroof of Chicago’s City Hall The roof of Chicago City Hall, completed in the spring of 2001, occupies approximately 20,300 square feet and contains about 20,000 plants from 156 species of sedum, forbes, grasses, shrubs, vines, and two trees. The city of Chicago, a leader in greenroof industry research, development and policy implementation, is co-hosting a conference in May of this year with support from the Chicago Environmental Fund, on «Greening Rooftops for Sustainable Communities: The First North American Green Roof Infrastructure Conference, Awards and Trade Show,» being organized by Green Roofs for Healthy Cities, a network of public and private organizations that has been working to develop the greenroof industry over the past four years. Among other things, the conference will provide opportunities to find out about training in greenroof design and implementation techniques, and to learn the latest greenroof research findings.

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