Green shroud

It is not everyday we see the surface area of a whole building covered with vegetation. For the parliament of the German Speaking Community in Eupen, they have put this into action on their new legislative building. FC&A explains more.


The parliament has a surface of 653m² altogether. On this area, modern architecture combined with advanced building greening concepts have created an impressive estate inserted between the historic main building and the park.

The parliament of the German Speaking Community in Belgium has been situated in their new residence in Eupen since last October. The former sanatorium had to be completely renovated before administration and fraction offices were able to move in. The historic structure was built in the first half of the 20th century during the reign of the emperors and had, due to the past political situation, both German and Belgian owners who used the building for different purposes.

The German Speaking Community in Belgium took possession of the building and the surrounding land although representative accommodations were missing. So in fall 2008 an international competition for architects topped off the modification and renovation. The winning atelier was Kempe Thill in Rotterdam supported by Artau scri d’architectures in Malmedy. An outstanding eye-catcher is the greening of the newly-built petition hall.

As the older and taller main building is situated behind the new petition hall and furthermore is built on a hillside, the roof surface of the newly-created building is visible for everyone. That’s why the planners decided to create vegetation on the walls and the roof. Thanks to this idea the plenary hall integrates itself perfectly to the renovated sanatorium and the landscape in general. Architects call it a “landscape project in front of a manor house within both the buildings have their own character but still complement each other”. A great view can be enjoyed from the plenary hall as well as from the main building.

Construction conditions

The newly-built plenary hall is a concrete building with 16cm thick insulation made out of PUR foam. The waterproofing of the roof was sealed root-proof with PVC, thus prepared the roof for the greening. The architect’s aim was to keep an even and consistent appearance of the facade and the roof greening.

Furthermore, they tried to let the different greenings fuse into one surface. To achieve this result, the planners had to find a supplier who was able to offer both facade and roof greening systems. The worldwide operating company Optigrün interational AG based in Krauchenwies, Baden-Wuerttemberg, met the architect’s expectations. With interaction of architects, technical department of optigreen and their regional manager in Belgium different possibilities were tested and the system solutions ‘facade greening’ and ‘lightweight roof’ were found suitable to complement each other.

Due to the guidelines, the vegetation and maintenance, the system solution ‘lightweight roof’ was chosen. This roof greening with a layer height of 5cm only weighs 53kg/m². The exact layer composition includes:

  • Protection and storage fleece type RMS 300
  • Optigreen drainage board type FKD 25 (25mm)
  • 3cm optigreen low density substrate type L
  • Pre-cultivated sedum vegetation mats

As an exclusive red-leafed vegetation was requested, a pre-cultivated sedum vegetation mat was fitted. This way the roof surface was unified immediately. Even the inspection chamber, which was installed to control the root drainage outlets, was being greened.

Wall attached facade

The crossover from wall to roof seems seamless at first sight because the grid at the end of the roof greening has just the same material and colour as the elements of the facade. Thanks to the mesh size the sedum plants have enough space to grow through the grid and therefore cover it optically.

The optigreen facade greening is a wall attached greening system without any connection to the ground. It’s based on substrate which brings a row of advantages: frost resistance for the plants, higher water retention, humidity float and more space for roots. The stock size of the facade elements add ups to 60 x 100cm. In addition there can be project-oriented customised sizes so project specific conditions can be considered as well.

Constructional requirements for the installation of the system solution facade greening is a static suitable wall or facade construction (with and without insulation), which can sustain at least additional 120kg/m². On these structures suspension rails can be installed and arranged with inspectional approved fixing devices. The optigreen suspension rails can, if constructional possible, be fixed directly on the wall. If not, bearing rails have to be used to install the optigreen suspension rails. At one of the objects in Eupen, the optigreen suspension rails were placed on a substructure. The facade elements can also be greened after they’ve already been installed on the wall, or just like in this object, pre-cultivated. For the wall garden in Eupen the facade units were pre-cultivated, which means that sedum plants were planted in plant containers several months prior to the commencement. In addition sedum sprouts were incorporated into the substrate.

Watering strategy

Wall attached facade greenings have to be cultivated regularly. The cultivate arrangements consist apart from water and nutrient supply of renewal pruning and replacement of single plants. The intensity of cultivation depends on the type of plant, the season and the plant growth which consequences upon it.

Determining for the perfect cultivation is a permanent and adequate water and nutrient supply, that’s why optigreen offers a watering system with integrated nutrition supply. For using this system, dimensioned domestic engineering (power and water feed) has to be available. To keep the fresh water consumption down, a computer controlled circuitry system proved itself. Humidity sensors measure the substrate’s humidity and release the water supply via trip hoses if needed. Concerning the project in Eupen, each facade is actuated individually. Also, every facade element has its own watering hose at a remove of 116cm. To control and monitor the facades each side is equipped with four temperature and humidity sensors.

Dream becomes a reality

The city ecologist’s dream got put into action and became reality in Eupen – a building which is greened all-around and on which the facades and the roof becomes one closed green cover. By greening all facades and the roof at the new building of the parliament of the German speaking community an impressive eye-catcher arose. Right after installation of the optigreen system solutions ‘wall garden’ and ‘lightweight roof’ last year the building was completely covered in green.

Share this article

Tagged under:
Login to post comments

About us

Future Constructor & Architect is a specification platform for architects and building contractors, which focuses on top-end domestic and commercial developments.

As well as timely industry comment and legislation updates, the magazine covers recent projects and reviews the latest sustainable building products on the market. Subscribe here.

Privacy policy

Latest updates


Sign up below to receive monthly construction, architecture and product updates from FC&A via email: