– Cooling of the surrounding air through the evaporation of rainwater
Temperature
Preservation and enhancement of plant and animal biodiversity
– Retention and storage of rainfall through the retention roof
– Availability of rainwater for planting
– Relief of public sewage systems
– Capturing of dust and
– Creation of additional green and recreational spaces in the heart of the city
Hubertus Schäfer and Verena Starke
GREENBOX
Landscape architects
The landscape architecture firm GREENBOX has been planning the design of the outdoor areas and the rooftop landscape of the House of Knowledge since 2020, after CROSS Architecture won the EU-wide competition. For Hubertus Schäfer, who founded the company 22 years ago in Bochum, it is a labour of love, as he studied in Bochum and Essen and gained his first professional experiences here. With 120 employees across six locations, GREENBOX is now one of the largest landscape architecture firms in Germany. STADTGOLD speaks with Hubertus Schäfer and project manager Verena Starke about their visions and ideas for the greenest public building in the city.
What are some of the tasks of a landscape architecture firm? And what makes GREENBOX stand out?
Hubertus Schäfer: In the broadest sense, we design
urban living spaces for people. This includes city centres, pedestrian zones, squares, promenades and parks. It’s not just about aesthetic design, but also about holistic concepts. GREENBOX’s mission is to create truly forward-looking urban spaces with climate adaptation in mind. A lot has changed in this area over the past few years. We have developed significant
new expertise within our teams, particularly regarding the concept of the sponge city. We are currently very busy with innovative concepts for rainwater, circular systems and recycling.
The House of
Knowledge showcases
what is possible today.
When did this shift happen? When did you realise that sustainable water management was becoming a much bigger focus in your work?
Hubertus Schäfer: If you take a closer look, you’ll see that the topic isn’t entirely new in landscape architecture. Clients now truly understand how crucial a sensitive approach to rainwater is in today’s city centres. Over the past six or seven years, we’ve found that we need to do much less convincing when it comes to the acceptance of more greenery, fewer paved areas, green roofs and façade greening.
And I believe the House of Knowledge project fits perfectly within this context because it allows us to showcase what’s possible in these areas. We want to explore every avenue available to us to make this place as sustainable and green as possible, while also creating a fantastic space in the heart of Bochum.
Did you already plan this approach when you participated in the competition?
Verena Starke: The concept of the green roof originally came from CROSS Architecture. However, when we joined the project, we redesigned everything from the ground up, integrating many forward-looking sustainability aspects.
What excites you most about this project?
Verena Starke: It’s simply a very diverse project, where you can combine an incredible number of innovative and technical aspects in a single place. We’re venturing into an experimental field that is inherently unique and entirely new in Germany. For me, being in charge of the project, especially in conjunction with the courtyard, presents completely new technical challenges. That’s what makes it so exciting.
Can you briefly explain some of the roof’s unique features?
Verena Starke: Atop the roof, a complete garden landscape with highly varied planting schemes is taking shape.
There will be trees, smaller shrubs, perennials, grass and lawn steps. On the Skydeck, an green roof with extensive plantings including sedum and herbs is also planned. This species-rich vegetation will create a shading and cooling effect for the building.
Water from the roof will be drained into two underground cisterns, along with rainwater from the courtyard. In the event of heavy rainfall, water is channelled into retention basins. If these threaten to overflow, the water is diverted into the cisterns,
where it will be reused for watering the roof during dry periods and for the building’s toilets. This means that the house has its own natural water cycle.
Can you estimate what impact these measures will have on the microclimate?
Verena Starke: Unlike a fully sealed roof, we have much less heat development here due to the plantings and the delayed run-off of rainwater, which creates some evaporative cooling, resulting in a cooler microclimate.
Hubertus Schäfer: This could even be calculated using certain simulation methods. Based on my experience, I foresee significant benefits from temperature cooling for the House of Knowledge.
So, what will be your favourite spot on the roof, Hubertus?
Hubertus Schäfer: We’ve planned a long table up top where many people can sit together. I can’t wait to sit down at that long table and open up a cool Fiege beer. Like I’ve said from the start: “I want to be sitting right there when the project is finished.” I’ve been looking forward to this moment the whole time.
A lot of people are wondering why you aren’t installing solar panels on the roof. What’s your response to this question?
Hubertus Schäfer: Well, now it’s actually possible to combine solar panels and green spaces. However, we decided to make the WHOLE roof a green space for the citizens of Bochum, as there are very few public green spaces in the city centre. This is also visible in the aerial photos. We simply want to create a vibrant place where people can really meet and where they can come together in the morning and the evening without any pressure to consume. This is precisely what our ideas like the “garden loggias”, the long table and the projection surfaces are intended for, and I very much hope they will be used frequently and with pleasure.
To what extent does digitality play a role in your planning, alongside sustainability and the social aspects of creating a new “place to be” in the city centre?
Hubertus Schäfer: Digital thinking has been deeply embedded in our firm’s DNA from its very inception. We are currently planning further projects that are also conceived as hybrids. At the House of Knowledge, we’re not just planning a new urban space on the roof; we’re also incorporating a digital layer from the outset.
“The garden is also digitally accessible.”
This is how the “loggias” came about, which are integrated into the green terraces. These loggias have a technical infrastructure with QR codes, where you can log in and access digital information in text and sound, creating a truly digital-analogue experiential space in the middle of the city. The roof of the House of Knowledge is merely the continuation of this very lively, multifaceted and hybrid concept of the entire building.
We are currently pursuing the integration of digital layers very intensively in many projects, such as at the IGA. The “IGA 2027 Metropole Ruhr” is an international garden exhibition and is currently one of our largest projects with a hybrid experiential concept.
Of course, this applies not only to the connection of the building with the roof but also with its entire surroundings, which is why you have now also been commissioned to help design Viktoriastraße and the connection to Husemannplatz. Can you already say how you will approach this or what the biggest challenge will be?
Hubertus Schäfer: The challenge is to engage people from all directions in the urban space and invite them in. Today, the area around the House on Viktoriastraße is primarily functional, with many paved areas and little space for people to linger. Moreover, a connection to the newly redesigned Husemannplatz is very important.
In front of the market hall entrance, we’re planning a grand staircase which we refer to internally as “the city sofa”.
Verena, where do you think your future favourite spot on the roof will be?
Verena Starke: I’ll make myself comfortable in one of the loggias in the area up top. I’m going to let it all soak in and immerse myself in one of the soundscapes. One of the truly delightful aspects of roof design is that there is something for everyone. Everybody can find the spot they need when they need it. Whether it’s a perfect place for chatting on the Skydeck, the terrace, the bar or the long table. Or a quiet loggia, where you can simply relax in solitude. I find that quite exciting too.
What challenges did you face in accommodating personal needs and limitations, such as for walkers, wheelchairs, strollers, etc.?
Hubertus Schäfer: For us, it goes without saying that this open space, which will be accessible to the public, will be barrier-free. Due to the topographical situation with a steep incline, it was a challenge to incorporate accessibility in a way that seamlessly blends into the garden character of the rooftop landscape. Thus, we turned necessity into a virtue and planned an “elevated walkway” with a maximum gradient of 6% rising through the greenery. Everyone is invited to stroll along this path, take in all the green scenery and enjoy the unique fragrant plants.
“The animals will settle in on their own.
How will it feel on days when it’s particularly hot or windy?
Verena Starke: The loggia area is a very sunny spot. In the height of summer at 35, 38 degrees, it can get hot here too. However, thanks to the plantings, it will never be as hot as on the asphalted squares in the city. Due to the height, it’s naturally windier than at ground level, but the trees will absorb quite a bit of it.
What about wildlife? Will they settle there naturally?
Verena Starke: There are areas below that are permanently wet. Moisture-loving species will likely settle there.
Above, we have taken care to plant a wide variety of species that provide food and a habitat for different types of animals. We aren’t explicitly introducing animals – they will settle in on their own. We are creating a variety of feeding and shelter structures for many insects and birds. The building also has nesting sites for birds and bats.
Are truly tall trees being planted there or will it take years before the roof reaches its intended state?
Verena Starke: A garden is always a living space and will take time to grow. For logistical reasons alone, but certainly also for cost reasons, it won’t be possible to bring the trees to the roof at their final height. The entire green space has a dynamic character and will develop and flourish over time. The planned trees will reach final heights of anywhere from five to eight meters.
Hubertus Schäfer: Of course, you also have to choose tree species based on their stability in connection with the planned soil structure.
What else would you like to see in future urban planning projects?
Hubertus Schäfer: It would be desirable for this project to set an example and for landscape architects to be brought on board much earlier so that sustainable and climate-adapted planning can be considered from the outset. The House of Knowledge is a prime example of how collaborative solutions in architecture and landscape architecture create unique added value.
Is there an international example of the direction you think things might go in the future?
Hubertus Schäfer: If you want to explore innovative architecture, landscape architecture and urban planning up close, I highly recommend visiting Copenhagen. The High Line in New York has also been a true catalyst for recognising hidden potential in existing urban areas. But our project at Zeche Zollverein, with the rooftop garden on the RAG headquarters, is also giving back exactly what was taken from the ground by the building.
Verena Starke: You can take individual elements from many international projects as models. But with the House of Knowledge, we also want to set an international example when it comes to rooftop gardens. We’re working here with clients and architects in a fantastic team It’s so much fun, and I’m firmly convinced that it will truly be a sight to see.
