In Heidelberg’s pioneering Bahnstadt district, KFWM Architekten BDA has completed Elf Freunde, a mixed-use urban quarter comprising eleven Passive House-certified buildings. Positioned between residential and educational developments, the ensemble demonstrates how architectural diversity can coexist within a coherent urban framework while meeting the ambitious aims of an environmentally minded district.
A Passive House district
Bahnstadt Heidelberg is one of the largest passive house neighbourhoods in the world. Covering over one square kilometre, it represents Heidelberg’s first fully developed Passive House district and serves as a testing ground for the city’s climate strategy under the Masterplan 100% Klimaschutz, which aims to reduce greenhouse gas emissions by 95% by 2050.
Energy supply
Within this context, Elf Freunde achieves energy consumption levels that are 50 to 80% lower than those of conventional residential buildings. Designed to the KfW Efficiency House 40 standard, the development requires around 40% of the primary energy permitted under current German energy regulations. This performance is achieved through a combination of high-performance building envelopes, triple glazing, and renewable district energy supply.
Heating and hot water are provided by a wood-fired combined heat and power plant in the adjacent Pfaffengrund district, while electricity is generated by photovoltaic systems integrated into the green roofs of the buildings. Rather than treating sustainability as a building-level intervention, these strategies help embed the project in renewable infrastructure at a district level.
Context and typology
Elf Freunde adopts the vertically structured perimeter block typology characteristic of Bahnstadt. This configuration defines a protected and private inner courtyard that is shielded from street noise. Here, Agence Ter has introduced fruit trees, perennials and edible plantings, using the landscape design to create semi-private and private outdoor areas. This shared green amenity is an essential component for high-density, low-energy urban living.
Spatial programming
The buildings are characterised by unique colouring and facade detailing that features setbacks and recesses which create space for terraces. These give the facade a sense of visual dynamism, while providing residents with additional outdoor spaces in an otherwise urban environment.
The buildings offer a range of flexible housing options designed to respond to diverse market demands: spanning one and two-bedroom apartments, work-life units, and townhouse-style maisonettes, among others. All of the apartments have an outdoor area and are positioned to face either southwest or southeast. Lift-accessible, there is step free access from both the building entrance and the underground parking area.
Commercial units are located on the ground floors of the buildings that mark the corners of the block. Oriented toward the street, the spatial arrangement helps reserve the inner courtyard for private, residential use. The floor plans throughout the buildings are designed to be flexible, with all ground level apartments offering fully adaptable layouts. This enables long-term usability and reduces the need for resource-intensive architectural interventions should the user needs change.
Sustainability
Rather than present sustainability as a technical addition, Elf Freunde shows how high-performance environmental standards can be integrated with architectural variation, landscape quality and urban density. As part of Heidelberg’s Bahnstadt, the development contributes to a broader experiment in climate-responsive urbanism and provides a replicable model for low-carbon city-making.
