Apartment Building, Basel, Switzerland

Competition Schliengerweg, Basel, Switzerland

In autumn 2022, the city of Basel announced an open competition for a housing development and kindergarten in Kleinbasel. The aim of the competition was to design a building as a pilot project, that could be constructed and operated in a climate- and resource-friendly way and achieve an overall energy balance of 'net zero' by 2040. In the sense of the circular economy, the client provided a catalogue of existing, used building components for reuse.

Under these guidelines for environmental sustainability, the design was developed by VOSS Architects in collaboration with Reichart Architekten, Basel. Our project responds to the urban context and the given conditions with a three-storey new building and recessed attic storey, consisting of two individual houses that are separated and equally connected by the central access. The access is generously designed, promotes exchange among the residents in the sense of a community space and is extended to a roof terrace on the top floor.

On the ground floor, the two kindergartens are each situated in a separate part of the building. Between them is the spacious entrance area for the apartments above, with staircase, lift and access to the bicycle storage rooms. In order to minimise the ecological footprint, the building was designed without a basement. The common basement uses, such as storage rooms or laundry rooms, were integrated into the apartments or located on the ground floor.

The upper floors are used exclusively for the apartments. The total of 6 flats with their own outdoor space and communal central zone are centrally accessed. On the first and second floors there are two flats each for four people. On the top floor there are two maisonettes, the northern one for four persons and the southern one for three persons.

During the development of the building, special attention was paid to the consistent system separation between primary, secondary and finishing elements, in order to be able to easily and completely dismantle all building components. The supporting structure of the project is designed as a modular hybrid building made of reuse steel, reuse concrete elements and timber. The façades are completely clad with reuse aluminium panels. The ground floor is differentiated from the residential floors above with the vertical structure of reuse trapezoidal sheets as façade cladding. The horizontality of the buildings is emphasised by the reuse of ceiling end panels. The French windows account for less than 30% of the façade area. The climbers to the balconies and terraces, with seasonally varying density, create a climatic buffer zone in front of the living spaces.

The building technology makes an important contribution to the sustainability and efficiency by minimising grey energy and using a low-tech concept. Photovoltaics and thermal collectors share the roof surface. 90% of the energy required for heating and domestic hot water is covered by thermal solar collectors. The heat generated in summer is stored in a solar tank (seasonal storage). The remaining 10% of the energy demand is generated by means of an air-water heat pump. The heat is distributed via underfloor heating. Night cooling in summer is naturally achieved via tilting windows (cross-ventilation) on the east and west façades.