The third dimension
If urban sprawl is to be kept in check, the only way left for a city to grow is up - the third dimension. And this also applies to green spaces. In Vienna, making additional allotments available to provide more green spaces is out of the question. This is why Vienna's policy is to turn all flat roofs into green roofs in the long run. Anyone who is interested in a green roof project can benefit from the city administration's expertise in this field. Roof-top gardens offer a number of benefits, such as new habitats for plants and animals, an improved micro-climate, and a cooling effect in summer based on increased evaporation.
The success of the City of Vienna's Gründach (Green Roofs) pilot project should provide an impetus for follow-up projects. Basically, the project consisted of turning an existing gravel-covered roof into a green roof which, over the long term, is not only environmentally friendlier, but also more cost efficient when designed correctly. If certain criteria are met, the City of Vienna grants funding of up to EUR 25 per square metre, subject to a maximum of EUR 2,200 for establishing green roofs.
The city's policy is to relieve the pressure on existing green spaces while retaining its zoning limits. To achieve this aim, it is necessary to think in the third dimension - green spaces high above the ground.
In future, all flat roofs are to become green roofs, as these have undeniable benefits.
- improve the quality of living,
- are able to retain 40 to 90 per cent of rainwater,
- improve the micro-climate though evaporation and cooling effect,
- provide enormous potential for highquality living spaces,
- reduce dust formation by binding dust from the air,
- purify rainwater,
- provide multifaceted habitat for plants and animals depending on the method of plantation,
- can use natural materials,
- protect part of the buildings' insulation layer from intense variation in temperature and UV beams,
- provide excellent thermal and noise insulation,
- can cope with intense rainfall because large amounts a water are partially stored or released with delay,
- offer added value when combined with photovoltaic or solar energy systems.
The environmental advisory centre (Umweltberatung) has produced a booklet which provides guidance for green roofs and highlights the benefits of roof landscaping.
Expertise on green roofs is also provided to the public by the City of Vienna's Municipal Department for Environmental Protection (MA 22). In addition to offering information to interested parties (e.g. architects or property developers), MA 22 also launches initiatives and projects to encourage green roofs in the city. A case in point: the plans for the "aspern Vienna's Urban Lakeside" development project included roof gardens on 100 per cent of all flat roofs.
Facts & Figures
- Grants for green roofs through the Vienna Municipal Department for Parks and Gardens (MA 42), dependent on the height, in centimetres, of the root-penetrable growing substrate on the newly greened roof area, grants range from EUR 8 to 25 per square metre, subject to a maximum of EUR 2,200.
- Minimum height for the root-penetrable growing substrate: 8 cm.
- Potential of rainwater retention by green roofs: 50-90%
- Status 2011: approx. 1,093 green roofs on 200 ha roof area
- Projects conducted with Schönbrunn school of landscaping, Vienna
DI (FH) Volker Schaffler
Tel. +43 1 4000 84269
Fax +43 1 4000 7997