What got you interested in historic buildings? Did you explore this topic as a student?
Yes, in fact the seed was planted during my studies in Delft. One of my first mentors was Professor Jan Molema. He had us analyse buildings that were considered masterpieces, but which had hardly been explored. We studied them to understand how they were architecturally constructed and what design decisions the architect had made. Molema was known for his analyses of Gaudí’s work, but he was also an admirer of Jan Duiker.
Duiker was the architect for the Zonnestraal tuberculosis sanatorium, which you later renovated with Bierman Henket. So you’ve been dealing with the building complex since you were a student?
Yes, in 1982 I was part of a group of students who edited the first real book on Duiker. There’s still no better book out there on the subject. Later when I worked in “ordinary” architecture firms, I continued my work on Zonnestraal, but it took a long time before it became a real project. It dragged on for decades.
Then in 1999 came the Van Nelle factory. I was unexpectedly asked to coordinate the conversion process of the buildings into a “design factory”– offices for creative companies. We developed the structural plan and designed the adaptive reuse of the warehouses and cafeteria ourselves. It was then that I realized: as an architect, you have a completely different role in conversion projects than in new construction. At first you don’t do any designing at all; you have to take care of many other things before that. For the Van Nelle factory, this included the development plan for the commercial district, because it was not originally zoned for office use. There were the city and provice administrations as well as the water authority to deal with.
A lot of preparation is required for such a project. Buildings are organisms that should not be tampered with until you know how the whole system works. This is also the message I give to my students in Delft: you shouldn’t always grab a pencil straight away. Our clients don’t necessarily understand that. If they call an architect for a new building, they’ll have a preliminary design in three weeks. Sometimes it takes us three or four months.
Apart from size, what were the main differences between Zonnestraal and the Van Nelle factory?
The restoration of Zonnestraal took much longer and was much more expensive than the Van Nelle factory. Do you know the book “Modern Functional Building” by Adolf Behne? In it, Behne distinguishes between rationalism and functionalism. He defines functionalism as tailoring the building to the programme. That’s what Zonnestraal is: there’s one type of room for the patient rooms, another for the treatment rooms, and another for the offices. Everything is custom-made; even the height of the parapets varies from room to room. But the more specific something is, the faster it becomes obsolete. Rationalism, on the other hand, means creating a multifunctional design based on a rational system. Brinkman & Van der Vlugt designed the Van Nelle factory according to this principle; after all, it could happen at any time that a product will no longer sell. So the rooms had to be easily convertible.
I still like to show my students a comparison of these two 90-year-old buildings. Ultimately it’s about sustainability: had Zonnestraal been built with recyclable materials, it could have been dismantled after 30 years, the usable components reused, and the rest recycled.
Duiker didn’t plan Zonnestraal for eternity. Does it even make sense to want to preserve such buildings at all costs?
With such a unique, legendary building complex, yes. In terms of its building physics, however, it’s a disaster. But you have to consider what it was used for: patients who needed fresh air, so the windows were always open. And now we’re whining about the facades not being insulated?
This also applies to the Van Nelle factory. Its users did physical work between large machines that radiated a lot of heat. Now it’s a business centre for the creative industry where everyone just sits at the computer all day. And what we call “room temperature” is 5 °C warmer today than it was 80 years ago.
So do you rely on users’ tolerance of the historic fabric? Do they have to compromise on comfort?
Not necessarily. At the Van Nelle factory, all office spaces have a double skin glass facade to preserve the building’s transparency. It’s a box-in-a-box construction with different temperature zones.
Not all buildings have the option of such solutions. Do clients ever commission you with a conversion that you find entirely unrealistic?
Of course, there are paradoxical repurposing ideas. Take the Sint Jobsveem warehouse in Rotterdam: it’s actually absurd to want to live in a warehouse. It’s made to shield goods from the outside world – but as a resident you want a view and fresh air. And yet, someone from the local council decided it should be a housing development. In the end, together with Mei Architects, we found a solution in the form of horizontal light wells, but it wasn’t obvious.
That sounds like a fairly pragmatic approach.
Of course, I could have spent my life working on high-end restoration projects like Zonnestraal, it’s like working in a nice ivory tower. But then you would be somewhat out of touch with reality. Early on I saw that I could achieve much more if I took on commercial assignments as well. It’s a much tougher world, but if you’re smart, you can funnel money that would otherwise be invested in new construction into adaptive reuse. There’s a lot of satisfaction in that. On the other hand, there can be friction with the historic preservation office, as was the case with our transformation of the Van Eyck orphanage in Amsterdam. But it’s as important to me that a building can be well utilized as whether the heritage lobby thinks its perfect. If a converted building isn’t usable, we will find ourselves in the same place 20 years from now.
You converted the modernist orphanage building into offices for the developer BPD. Was this a big challenge or was the building well suited for this new function?
Actually, it was quite doable. The tenant was looking for a building that suited its new working style with creative teams and informal working groups. The former orphanage fits like a glove! The teams often hold their meetings in the reading nooks that Van Eyck planned for the children back in the day.
The building physics were more difficult, because the concrete elements are literally in the facade: outside in the cold, inside in the warm. They should have been completely wrapped in insulation, but that wasn’t an option. In the end, we combined a geothermal heat exchanger with underfloor heating and a solar collector on the roof – and even achieved an “A” energy label.
The orphanage dates back to 1960. Has the appreciation of post-war buildings changed over time?
Yes, absolutely. At TU Delft we have even started looking at buildings from the 1970s and ’80s. Just as I found the 1920s interesting as a student, today students find the 1980s exciting. In the Dutch historic preservation system, this period is referred to as “Post 65”.
And yet, you supported the partial demolition of the Lijnbaan shopping street in Rotterdam in favour of the Forum project, which you worked on together with OMA. Wasn’t it worth preserving?
Naturally I asked myself the same thing. I even wrote an opinion piece for the city and the historic preservation office on why I thought demolition made sense. But the ingenious urban planning principles of Van den Broek & Bakema failed to unfold on this later part of the Lijnbaan. It had to accomodate a public square with an old plane tree, the distance between the shops was too wide, and part of the pedestrian zone was one flor below street level. It just wasn’t working anymore.
So far we have mainly addressed buildings of great architectural value. But there are many less remarkable 20th century buildings. How should they be dealt with?
As far as office buildings go, adapting them for use as apartments seems obvious to me. After 2008 we had a lot of office vacancies in the Netherlands. Just as things were looking up, corona arrived. Now it’s assumed that employees will only work at the office two days a week. I dare to predict that there will be both major office vacancies and – especially among young people – major housing shortages.
For example, we planned the adaptive reuse of the GAK administration building in Amsterdam. It now holds 650 very small condominiums for young professionals. Of course, the question is whether tiny apartments will stay in demand. Consider the small flats which people were scrambling for after the Second World War: nobody wants them anymore.
How about those post-war residential buildings – should they be preserved? It’s often said that restoration is more expensive than demolition.
It’s a double-edged sword. Refurbishing them is expensive, but tearing them all down isn’t an option. When you consider that 8 % of the world’s CO2 emissions come from cement and concrete production alone, it quickly becomes clear that a building needs to stand for at least 70 years until its ecological footprint is compensated for. Currently, the golden rule in the Netherlands is: residential buildings stand for 50 years, offices for 30 years, shops for 10 to 15 years. I advocate a more accommodating approach to energy regulations for older buildings. Just as we speak of “grey energy” we also have to speak of “grey CO2 ” and adjust the calculations accordingly.
Is that something you want to pass on to your students in Delft?
The students come to me on their own about it! Young people are starting to think that our way of building is crude nonsense. There’s a reason why nearly a quarter of architecture students at TU Delft do their degree in our studio [Heritage & Architecture].
What I do want them to know is that they should not always aim for the optimal state, because that would be a death sentence for old buildings. The more important question is: How much better will the energy balance be as a result of restoration? If you can ensure that the entire building stock consumes 30 % less energy, you will have achieved much more than if you only build energy-neutral new buildings. I like to compare it to a clogged sink with a dripping faucet filled with dirty water. The dirty water is the existing building stock, and the drips from the tap are new construction. Of course, it’s great if those drops are squeaky clean, because in the long run they’ll fill the sink. But in the short term, dirty water remains a problem. If you want to achieve success relatively quickly, you have to upgrade the building stock. Saving up to one third of energy in existing buildings and converting offices into living space: I believe that is our mission for the next 20 years.
