Schlieren’s school giant, Kalktarren, awakens

Around 800 pupils attend the Kalktarren school complex in Schlieren, one of the largest school buildings in the canton of Zurich. The complex is now set to undergo its most far-reaching transformation since it opened in 1970. On 28 September 2025, voters gave the go-ahead with 74 per cent voting in favour. The budget amounts to 45.66 million Swiss francs.

The refurbishment is comprehensive. The building envelope, building services, fire safety and earthquake resistance will be brought up to the latest standards. At least eight new classrooms, as well as additional multi-purpose and group rooms, will be created to accommodate modern educational approaches. The striking exposed concrete façade, an architectural hallmark of the building, will be retained. On the roofs, the reinforcement of the supporting structure will create space for large-scale photovoltaic systems, which will cover part of the building’s own energy requirements in future.

Learning without interruption
A school of this size cannot simply be shut down. The planning team has therefore devised a clever phased approach. The work will be carried out in a northern and a southern section, alternating and in a coordinated manner. Around twelve classes will be temporarily accommodated in modern portable classrooms on the site, without causing any significant disruption to school life. Access for classes, teaching staff and clubs will be guaranteed throughout the entire construction period. The planning demonstrates that a major refurbishment and the smooth running of the school need not be mutually exclusive.

Energy from the Limmat Valley
With this refurbishment, Kalktarren is permanently phasing out natural gas and heating oil. In future, Limeco will supply district heating, generated from the waste heat of the waste-to-energy plant in Dietikon. What is still a vision elsewhere is being put into practice here. Renewable heat from the regional network flows through a growing district heating network that is gradually being rolled out across the Limmat Valley. Kalktarren is thus becoming a flagship project of the city’s Net Zero Strategy 2040.

Part of a wider transition
Around 48 per cent of greenhouse gas emissions within the Schlieren municipal area are generated by buildings. Seventy per cent of the city’s buildings are still heated using fossil fuels. With Kalktarren, the city is sending a clear signal that this is changing. The school complex is not only the city’s largest renovation project in years; it is also proof that sustainable building is possible within the existing built environment and that a municipality can develop further as a whole by following this path. Instead of demolition and new construction, a conscious decision was made to preserve the existing building fabric and enhance it. A decision that conserves resources whilst maintaining urban continuity.

The timetable
Planning applications and tenders have been underway since early 2026. The ground-breaking ceremony is scheduled for mid-2027, with completion due by the end of 2029. Schlieren is building. And it’s well worth taking a look.

Text: Christoph Grüninger • Image: Architron