As light as Airby | 12.03.2016

Bushof und Bahnhofplatz Aarau

From the architect, vehovar & jauslin architektur:

People who exit the train station should immediately realize they are in Aarau. The spacious, open and urban station forecourt is a pleasant and bright place for all, structured by islands of light and unique materials. Like a clearing in the woods, the diaphanous air cushion roof, which is open at its center, spans over the forecourt. It protects the passing travelers beneath, but is airy enough that the waiting area does not seem like an enclosed hall.

Zurich, February 2014

As the central public transport hub for the entire region, the train station in Aarau serves as a point of departure, arrival and transfer for more than 40,000 train and bus travelers every day. Due to assorted small structures, street furniture, art objects and planters that had gathered over time, the station forecourt was barely still perceived as a public open space. Bahnhofstrasse, the street leading to the train station, was a spatially defining axis dominated by car traffic, thus cutting the space off from the surroundings. That is why a new station forecourt with a bus terminal and optimized public access was also envisaged along with construction of the new train station. After lengthy preparatory work in close dialogue with various interest groups, the Aarau populace approved the project with an overwhelming majority in 2009.

The Station Forecourt

As part of the reorganization, the forecourt of the train station was completely redeveloped. The result is an orderly, open square with a bus station at its center. The buildings that were once relegated to the periphery, and the train station itself, now have a new address on the station forecourt. And Hotel Aarauerhof is right in the midst of it. In this way, two compartmentalized areas are now joined to form the largest square in Aarau – an urban outdoor space that, because its area has nearly doubled in size, is now commensurate to its significance within the city.

The paving is as uniform and accessible as possible in order to fulfill the diverse requirements for a well-maintained and friendly station square. In this way, the forecourt becomes a single entity and also succeeds in integrating Bahnhofstrasse as part of the square.

The necessary furnishings with seating elements and garbage cans take the form of small islands in the space, which are highlighted at night with energy-saving LED lighting. The relaxed appearance prevents the now tidy place from immediately becoming cluttered again. The red, tulip-shaped seating elements are like refreshing bouquets of flowers that confer a feeling of spring even in cold and wet weather. As a result, the station forecourt invites you to linger and pause, acting as an urban counterpart to the cantonal school park.

Bus Station with an Impressive Roof

The image of the new station forecourt is unquestionably defined by the roof over the actual bus terminal, a canopy that the locals already affectionately call the “cloud.” Its organic shape with a clear view to the sky at its center originates from the desire to not place an upper limit on the square, but to welcome travelers in a friendly and bright environment. “From the beginning, we wanted to create a spatial atmosphere under the roof that resembles a clearing in the woods. In order to greet the passengers in a bright and friendly environment, a very light, diaphanous material was selected,” explains architect Mateja Vehovar.

We chose an air-supported membrane cushion made of the synthetic material ETFE. Such membrane roofs are not only easily designed in various forms, but are also extremely light, durable, weather-resistant and self-cleaning. The expansive cushion is held up from within by a freeform steel construction. An irregular network of steel cables across the outer surfaces gives form to the air cushion. The necessary utility lines for drainage, lighting, recirculating air and measurement technology run invisibly inside the construction. Thus the roof appears light and airy instead of looking like a technical installation. For all the materials used, we paid attention to the issue of sustainability. This also holds true for the air recirculation system. “Thanks to the excellent air tight quality of the cushion construction, the task of the ventilation system is nearly limited to solely adjusting the air pressure in the roof to suit the changing weather conditions,” explains Gerd Schmid from the Radolfzell engineering firm formTL, which was responsible for the structural and technical design of the roof.

“Since it’s often foggy in the Central Plateau, the blue coloring of the upper membrane is meant to ensure that a bit of blue sky always floats above the buses,” says Vehovar. For the blue upper and clear lower membranes, the architects and designer Paolo Monaco together expressly developed slightly differing, seamless printed patterns. Their appearance, which is reminiscent of foam bubbles, makes it possible to allow the structure of the entire roof to be read from below and, at the same time, to provide shade and prevent the unwanted emission of direct artificial light into the night sky.

The roof exudes lightness and joy. Perhaps also because it responds so naturally to the light of the surroundings: Whether through the play of light and shadow, through the light reflections of its own lighting and the sun, or because passing clouds cast fleeting images upon the roof.

The world’s largest membrane air cushion represents a unique mixture of functional, advanced technology and a varied, delightful play with people’s sensory perception. It is more than just a mere bus terminal, it is functional art in urban space – a landmark for Aarau.