BLACKPRINT: Mr Ehling, the Collegium Academicum in Heidelberg is breaking new ground in the creation of affordable, self-managed and environmentally sustainable housing. How did the commission come about and what particularly appealed to you about it?

Frederik Ehling: The project started with a group of students who were experiencing the housing shortage first-hand and decided to tackle the problem together. With this mindset, they got going and organised a workshop with various architecture firms as part of the International Building Exhibition in Heidelberg, which was just getting started at the time, to sort through their ideas and flesh out their initial goals. The students did not have a finished list of requirements like an investor, but first had to figure out what they wanted. Ultimately, the group chose us because the chemistry was right and our expertise was a good fit. We shared many of the group's participatory, collaborative and sustainable approaches. Added to this was the research project by Hans Drexler, the founder of DGJ, on metal-free solid wood constructions based on traditional carpentry joints, which can be implemented sustainably without metal components, using only wooden pegs and dowels. His construction system is called ‘Open Architecture’. This constructive idea convinced the group. From that moment on, we developed the construction project together, step by step.

BLACKPRINT: What steps were then crucial for the development of the design?

Frederik Ehling: First, we held numerous workshops with the group to formulate the specific requirements and record them in a specification sheet. Existing funding requirements, such as a maximum of four people per flat share or at least 14 m² per room, also helped us to structure the design. In close consultation with the students, we then developed a prototype for a four-person shared flat that can be repeated as often as desired. Based on this prototype, a building for 176 students in 46 shared flats was ultimately created. What is interesting is that we did not design the building geometry in detail in the traditional way from an urban planning perspective, but rather the other way around: we started with the materials, the construction and the real living requirements and developed the form from there. The façade of movable wooden slats reflects this lively, constantly changing use in a way that is visible from the outside.

BLACKPRINT: How exactly are the individual shared flats structured?

Frederik Ehling: Each individual shared flat consists of a communal area in the centre, around which individual rooms and sanitary facilities are arranged. The individual rooms consist of two parts: a fixed core zone with a bed, wardrobe and desk, and a flexible zone measuring 7 square metres that can be opened up, partitioned off or reconfigured as desired. Interior walls can be moved or added by the residents themselves, so that each shared flat can negotiate its own space requirements, use and spatial configuration.

BLACKPRINT: Timber construction, circular principles, low-tech strategies and a high degree of prefabrication play a decisive role in the project. How do you assess this in terms of sustainability?

Frederik Ehling: The building is a skeleton structure made of prefabricated wooden elements, each three metres high and up to twelve metres long. This construction method not only allows for flexible room layouts, but also ensures high resource efficiency. Thanks to the use of wood as the sole material, the building can be dismantled, reused and thus recycled. We deliberately avoided composite systems so as not to complicate subsequent dismantling. Reinforced concrete is only used in specific areas of the floor slab and in the pergola for escape routes. The system thus combines ecological material strategies with a high degree of adaptability and a construction method that is resource-efficient and sustainable.

BLACKPRINT: Do you consider timber construction to be the key to sustainability?

Frederik Ehling: Yes, absolutely. Wood is environmentally friendly, binds CO₂ and can be dismantled. For us, single-species construction is key: it allows buildings to be easily adapted, recycled or reused later on. Prefabricating the modules significantly shortens construction time while reducing energy and material consumption on site. In combination with our system for metal-free wood connections, ‘Open Architecture’, well-thought-out low-tech solutions and maximum flexibility, we have created a building that is both environmentally and functionally sustainable. This was offset by a longer planning phase, in which all parties involved participated intensively. However, this additional effort has paid off in terms of the significantly higher quality of the implementation and the high level of user satisfaction.

BLACKPRINT: And what about the manufacturing costs?

Frederik Ehling: The target was a warm rent of €270 per room. We were able to achieve this goal because the project was realised on a cost-covering basis, but without profit. Minimal additional costs only arise if higher-end fittings are used. Overall, however, the system is practically cost-neutral. At the same time, the energy standard is also impressive, as the building is almost passive house-compatible, meaning that heating is only required for a few days a year. This shows that economically and ecologically responsible construction is feasible.

BLACKPRINT: And how do the residents rate the building today?

Frederik Ehling: There are two levels to this. Firstly, the building was examined as one of around two dozen projects as part of the ‘Variowohnungen’ research programme run by the Federal Institute for Research on Building, Urban Affairs and Spatial Development, meaning that the results are documented and evidence-based. Secondly, a long-term psychological study is being conducted with surveys of the residents. The direct feedback has been very positive. The students particularly appreciate the opportunity to actively design the room layout. Initially, there was considerable reluctance with regard to sound insulation. But after a few tests, the residents were able to experience first-hand how well the construction works. The walls are almost comparable to normal drywall. One student moved the flexible wall eleven times within a year, depending on her needs and usage! This makes it a living laboratory for communal and self-determined living.

BLACKPRINT: This flexibility is truly exceptional. In a way, you have done pioneering work...

Frederik Ehling: Yes, absolutely. The project is a prototype for new approaches to housing construction, offering a high degree of sustainability and flexibility. And we have developed processes and designs that can also be applied to other construction projects. We have taken a similar approach, for example, in the cooperative project ‘WohnWerk’ in Mannheim and in the housing project ‘Gemeinsam Suffizient Leben’ in Frankfurt am Main. There, too, the metal-free timber construction method saved us a lot of planning time and enabled flexibly scalable floor plans.

The cooperative housing project ‘WohnWerk’ is designed as a five-storey timber construction with flexible floor plans.

BLACKPRINT: The idea of serial prefabrication is not new historically; similar approaches already existed at the Bauhaus...

Frederik Ehling: Yes, similar concepts were already being considered 100 years ago. However, after the 1960s and 1970s, the image of serial construction deteriorated significantly. We have now moved on and learned from the mistakes made back then. Today, we can further develop the idea with new materials and sustainable strategies and adapt it to current housing needs.

The housing project ‘Gemeinsam Suffizient Leben’ (Living Sufficiently Together) in Frankfurt am Main combines opportunities for individual development with communal living arrangements.

The ‘Raumkante’ in Heidelberg's Südstadt district was constructed using a timber frame element system. It offers socially acceptable living space in an urban location with affordable rents and high energy efficiency.

BLACKPRINT: In addition to communal living arrangements, DGJ also carries out other construction projects. What connects the various projects?

Frederik Ehling: For us, architecture is always an interplay of ecological, economic, social and cultural aspects that must function in balance. To achieve this, we think and work flexibly, participatively and sustainably, with a focus on timber construction, material suitability and user participation. We consider sustainability to be a non-negotiable factor. However, the decisive factor for the life cycle performance of a building is not so much the energy standard, which can now be planned well, but above all the construction itself. Wood plays a central role in this. But the material alone is not the ‘game changer’; sufficiency, usage requirements and prioritisation are just as important. However, we never act dogmatically! It is important that we implement the major levers correctly; the remaining 20 per cent can then be accepted as a compromise. This is the only way to achieve true sustainability.

BLACKPRINT: Despite the current housing shortage, particularly in university towns, such concepts or similar ones are rarely implemented. What factors prevent this?

Frederik Ehling: There are probably several reasons for this. On the one hand, there is a certain inertia in many institutions, meaning that changes are only accepted slowly. On the other hand, there is often a lack of experience with new construction methods, and production capacities for modular or flexible timber systems are limited. In addition, participatory processes are time-consuming. It was easier for the students because they were able to contribute a lot of commitment without having to calculate labour costs. Such processes are much more difficult to implement for traditional property developers, as time, budget and risk are more limited. In principle, however, it is feasible.

BLACKPRINT: And what does it take to promote sustainable construction instead?

Frederik Ehling: In addition to institutional inertia, the fact that ecological costs are often not factored into prices is a major obstacle. Mineral-based construction methods therefore appear cheaper in the short term and are considered by many to be a safe solution. In order to establish sustainable construction more firmly, we need convincing practical examples and the courage to break new ground. This is the only way to show that flexible, sustainable and participatory forms of living are realistic and economically viable!

BLACKPRINT: Mr Ehling, thank you very much for talking to us!

The interview was conducted by Robert Uhde.