The Heimatmole building collective integrates living, working, and leisure under one roof in the heart of Hamburg’s HafenCity.

BLACKPRINT: On your website, you write that your team’s mission is to rethink housing and its urban context. What exactly do you mean by that?

Michael Ziller: We always consider housing in relation to its surrounding environment. A sustainable quality of life arises from the balance between living, working, education, leisure, supply, and mobility. Yet the strict separation of these functions—rooted in modernist planning—continues to shape our building regulations today. Our aim is to overcome this division and reconnect individual lifestyles with their neighbourhood context. It is precisely diversity and mix that create quality of life, both within a building and in the urban realm. That’s why we always think housing and urban design together and first ask: How does neighbourhood emerge? What spaces foster interaction—between houses, on rooftops and at ground level?

BLACKPRINT: Many of your projects are developed in collaboration with building groups or housing cooperatives. What appeals to you about that, and what opportunities do you see in such collaborations?

Michael Ziller: It’s closely tied to how one wants to live oneself. If you take that seriously, it naturally leads to greater functional diversity and more communal concepts. This mindset applies especially well to cooperative or collective housing. Such projects often have greater substance because they’re driven by genuine needs and the commitment of future residents. The result is housing models that work over the long term—socially, economically, and ecologically.

BLACKPRINT: With the recently completed „Heimatmole“ project, you’ve created an urban collective building in Hamburg’s HafenCity that integrates living, working, and leisure under one roof. The building provides inner-city housing for sixteen Hamburg families, who are both owners and developers. What was your design intent for this project?

The building’s “green façade” enhances living quality, improves the microclimate, and creates space for neighbourhood interaction.

Michael Ziller: With Heimatmole, our aim was to combine urban density with green quality of life and to rethink the relationship between living, working, and community—almost like a village in the city. What made the project particularly exciting was that the building collective came to us with a clear vision: they wanted generous greenery, shared spaces for interaction, a lively roofscape, and flexible layouts that could adapt to different life stages. From these aspirations, we developed a concept centred around planted balconies facing the courtyard. This “green façade” acts as an extended “green room”: it enhances living comfort, improves the microclimate, and fosters encounters among neighbours. Uniquely, the balconies connect not only to the stairwell but also to one another, encouraging vibrant community life.

BLACKPRINT: Adjacent to these balconies and stairwells, you also created special “switch rooms”…

Michael Ziller: Yes, these are flexible units that can be booked or used as guest rooms or workspaces. Together, these elements form a building that combines urban qualities with neighbourly closeness and accommodates individual lifestyles. What’s remarkable is how well the concept works in practice: residents support one another and appreciate the range of possibilities their house offers.

Concept sketch of the “switch rooms.”

BLACKPRINT: Heimatmole is a KfW 55 energy-efficient building. It uses heat exchangers and generates power via rooftop photovoltaics. The roof, however, also serves an important social purpose…

Michael Ziller: Yes, that was crucial for us. Typically, even green flat roofs are dominated by building services. Instead, we consolidated all the systems compactly within the stair core to free up usable outdoor space. This created a roof terrace with an outdoor kitchen, gardening areas, and places to gather or simply linger—with a stunning view over the Elbe, the port, and back toward the city. The rooftop is used intensively, even on cooler days. A strong community has formed up there—and that’s no coincidence. In such a collective, people get to know each other during the planning phase, rather than after moving in. That takes energy, and the process isn’t always easy, but it’s worth it—for the community and for us as architects. The result is so much better that we’re always eager to take on such challenges again.

The shared roof terrace offers sweeping views over the Elbe, Hamburg’s harbor, and the city.

BLACKPRINT: How difficult was it to develop a shared solution that everyone could support?

Michael Ziller: Such collaborative projects only succeed when moderation doesn’t rest with us as architects. In this case, the KiezKompanie Hamburg took on that role—and did an excellent job. This allowed us to plan the project from Munich and travel to Hamburg only for key meetings. Designing architecture and moderating group dynamics simultaneously would have been one task too many. It’s also beneficial to have an external, neutral party to balance differing viewpoints. That keeps us as designers more flexible—and ultimately benefits the project.

The Heimatmole project can also be understood as building within an existing urban fabric.

BLACKPRINT: Working with existing structures is another recurring theme in your office. How do you approach such projects, and what role does sustainability play?

Michael Ziller: For us, every project begins with understanding its context—its physical setting and the people who inhabit and shape it. In that sense, even Heimatmole can be seen as “building in the existing fabric.” Starting from that understanding, we can design purposefully and set the right course for how a place will be used. Sustainability then emerges naturally as a result of this process.

BLACKPRINT: A strong example of this approach is your recently completed Gelber Block in Munich’s Westend, where you added and modernised a cooperative housing block originally built in 1927. The four- to five-story complex was expanded with two prefabricated timber stories, creating 45 new apartments on top of the existing 169 units.

Michael Ziller: The key was working directly with the cooperative on site, in close dialogue with residents. In this way, we learned firsthand what was missing and what was needed. At the same time, we could explain the benefits the modernisation and extension would bring—new elevators, balconies, improved layouts. The process also revealed that another cooperative complex nearby, built in the 2000s, is now home to many older residents whose children have moved out. For them, we created smaller new apartments so that larger ones could once again accommodate young families. Here, sustainability emerges not only structurally but socially. Another key aspect was the ground floor at Georg-Freundorfer-Platz: originally designed for retail in the 1920s, it had been converted into apartments. We have now transformed three of those units into a neighbourhood centre and two social offices. The community centre is run by the nonprofit association Generation-Appropriate Living with the Munich-West Housing Cooperative e.V., and the social office assists cooperative members with various issues. Even the existing flower shop was preserved as an identity-forming element to strengthen the vitality of the ground floor.

Timber surfaces on ceilings, floors, and window frames create a pleasant indoor climate and high living quality.

BLACKPRINT: Timber plays an important role in this project. Do you select the building materials yourselves?

Michael Ziller: Material selection is just as crucial as the creative process itself—it’s integral, not secondary. We make those choices together with the clients, as they strongly influence a project’s success. We prefer minimally processed, durable materials that can be disassembled or reused. Accordingly, we like working with timber—pure or hybrid, depending on the project. Prefabrication and modular construction bring new opportunities to rethink sustainability and efficiency while improving and accelerating the building process. It’s important, however, to involve small manufacturers and help them evolve. The current focus on industrialised construction, by contrast, worries me—there’s a risk of dependency and standardisation that drives up costs without adding quality.

BLACKPRINT: Your cooperative project Grünwald in the Munich suburb of the same name takes yet another approach. There, you replaced a 1950s cooperative housing estate with a new development of fourteen houses grouped around three small squares, each providing 10 to 14 apartments.

The Grünwald project comprises fourteen houses arranged around three small squares, each with 10 to 14 units.

Michael Ziller: The project’s central idea was its setting—in an area known more for luxury villas and high-profile residents than for cooperative housing. Public space again plays a vital role here, with shared outdoor areas including a large wildflower meadow that’s mown only once a year. This gives the ensemble an almost village-like character—something you wouldn’t expect in such a block-like urban setting. Interestingly, the municipality of Grünwald has since adopted this concept for its public open spaces.

BLACKPRINT: Looking ahead, what issues will shape architecture in the coming years—and how can the field become more sustainable?

Michael Ziller: Especially in times of change, a holistic, process-oriented mindset is crucial—one that integrates social, economic, and societal shifts equally. Instead of pursuing rapid urban expansion, as in the 1970s, we should learn from that era and plan consciously for the long term while remaining adaptable. That also means accepting that architecture inherently involves inertia: what we build today should ideally last a century—and then be adaptable again. Balancing permanence with flexibility in response to societal change will be the key challenge of the coming years. It demands long-term, forward-looking political decisions. Yet we often sense that departing from familiar paths initially causes uncertainty or even fear. That’s why change management is so important: we must make visible the improvements that transformation can bring. From this, we want to craft a positive narrative—one that encourages and inspires curiosity for what’s next.

BLACKPRINT: Mr. Ziller, thank you very much for the conversation.

Interview by Robert Uhde.