Triple use of the roof: Open Space, Green Space & Photovoltaic Energy

Grossraumbüro Perspektive Nachbar (C) IKI AG Ressourcenorientiertes Bauen BOKU Wien

The extensively greened roof creates a cozy atmosphere and additionally produces green energy.

After almost three years of development work by ten partners, the research project’s initial results were presented at BOKU Wien: the plant-filled roof terrace creates a pleasant, comfortable environment. The photovoltaic pergola with semi-transparent glass-glass modules provides shade and produces green energy. The project supports sustainable urban development. Further implementation projects are now being sought.

Producing renewable energy, offsetting increasing soil sealing, improving the micro-climate, storing CO2 and rain water and extending the life of the roof membrane – a combined roof system should do all this and much more, according to the project’s starting position. A multi-disciplinary research team developed the system concept that was installed at the test site on the BOKU roof terrace.

The wooden test facility at BOKU does not yet represent the final architectural design. But it is already clear how the solution works: the previously underutilised terrace has become an attractive recreational and meeting place with a noticeable three to five degree temperature difference. In the test garden, five tons of CO2 are saved every year thanks purely to the photovoltaic system, without taking account of the CO2 retention properties of the plants and soil. The plants also act as a fine dust filter.

New recreational area for building occupants

Irene Zluwa, IBLB Vegetation Technology Faculty, BOKU Wien. The final design of the photovoltaic roof garden consists of a green roof structure, a pergola made of wood or steel and a canopy with photovoltaic glass-glass modules. A photovoltaic roof garden unit measures around 56 square metres and can be endlessly multiplied. It provides about 5,500 kilowatt hours of green energy a year, or enough to supply one to two households.

The costs including plants, steel girder construction and photovoltaic system are around EUR 79,500. At EUR 1,400 per square metre, the photovoltaic roof garden costs roughly the same as a conservatory. But for the same price, it provides both green energy and pleasant, green surroundings.

Project partners

  • tatwort Nachhaltige Projekte
  • Institut für Ingenieurbiologie und Landschaftsbau der BOKU Wien (IBLB)
  • Fricke
  • Raintime
  • Ertex Solar
  • Institut für Konstruktiven Ingenieurbau, AG Ressourcenorientiertes Bauen der BOKU Wien (IKI)
  • Treberspurg und Partner
  • ATB Becker
  • voestalpine Krems
  • CES clean energy solutions
  • Wien Süd


Susanne Lins

tatwort Nachhaltige Projekte GmbH



This post is also available in: German