Visualisierung des Primarschulgeländes und der Turnhalle

Ecological densification - new Bubenholz school complex

Building densely and ecologically at the same time: This is what the new Bubenholz school complex in Opfikon ZH stands for. The innovative hybrid building on the roof of the airport highway shows how timber and concrete harmonize perfectly - and together create the building structure of the future.

Space for new buildings is scarce in urban areas. Accordingly, redensification, i.e. the use of previously undeveloped areas in residential areas, is becoming increasingly important. At the same time, the focus is increasingly shifting to sustainable construction. The new construction of the Bubenholz school complex in Opfikon in the canton of Zurich shows how innovative, environmentally friendly solutions can be created in a limited space. "The flagship project proves that building with ecological responsibility is possible even in confined building conditions - and even brings numerous advantages," says Svein Kåre Sundhagen, Project Manager Timber Construction at Implenia. "Timber construction is perfectly suited to this complex situation on the tunnel roof."

Bubenholzpark: redensification on the tunnel roof

Bird's eye view of building location

The Bubenholz Park, built in 2004 on the roof of the airport highway, connects Opfikon and Glattbrugg. At this urban interface, the new Bubenholz school complex brings the two districts even closer together. The school complex comprises two compact buildings, the main school building and the building with common rooms such as the gymnasium and singing hall, which frame the green space on the highway cover. The main school wing is located on the western edge of the site next to the tunnel. Thanks to the staggered, diagonal layout, all classrooms face the green space. The wing with communal facilities such as the gym and library forms the northern end of the green space. It faces the highway with a small number of carefully positioned openings, making the building an ideal noise barrier. The green spaces between the buildings offer beautiful open spaces for the pupils and also improve the air quality in the surrounding area.

Timber as a load-bearing element

The visible in-situ concrete beams and timber supports

The fact that timber plays a prominent role in this project is evident from the wooden façade, which beautifully complements the green space. "Probably the biggest challenge in this project was building on the tunnel roof and the associated weight restrictions," explains Sundhagen. "The low dead weight and the structural properties of the timber make it possible to build multi-storey structures with large spans." The Implenia teams have developed a solution based on proven composite structures that relies on visible load-bearing timber columns with exposed concrete beams. This allows the timber and concrete materials to fully exploit their respective advantages - and the tunnel roof is subject to minimal load thanks to its low weight. The collaboration between Implenia's various specialists was efficient and the result was of high quality. "As we have all the expertise in-house, we were able to find the right solutions," says Sundhagen.

Timber as a driver of sustainability

"We only use Swiss timber from sustainable forestry for the ceiling structures, the supports and the hall beams," says Sundhagen. "In this way, we support domestic producers - and ensure that we don't consume more than grows back." However, timber is much more than a renewable raw material: it is light, stable and has a low environmental impact compared to concrete or steel. Timber also stores carbon, which reduces greenhouse gases. Inside, wood creates a more pleasant indoor climate and has good thermal and acoustic properties. "For the future, I hope that more building owners will recognize the ecological and economic benefits of timber and hybrid buildings," says Sundhagen: "The increased use of timber in the construction sector is an important step towards achieving national and international sustainability goals." And as a successful model project, the Bubenholz school complex points the way in the right direction.

Image source & visualisations: Nightnurse Images AG

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