The municipality of Leiden aims for circular construction, but how do you reconcile that with the growing demand for housing? For the Kennisatelier Duurzaamheid, master's students from Industrial Ecology are investigating whether the municipality can build enough houses up to 2030 and still use half as many materials. ‘High-rise buildings have a much higher demand for materials than terraced houses.’
With its dark red lower stories and two impressive towers, it is Leiden's new eye-catcher: the multifunctional building Lorentz next to Leiden Central Station. It was awarded a BREEAM Very Good certificate, an indication of the building's sustainability. But does high-rise fit in with the municipality's circular plans? Students of the master's programme Industrial Ecology Master's are trying to clarify the matter and come up with some interesting insights.
Master programme Industrial Ecology
Industrial Ecology comes forth out of the Leiden-Delft-Erasmus Universities collaboration. Industrial Ecology is an emerging scientific discipline that takes a systemic approach to sustainability problems. An interdisciplinary approach, integrating an engineering, environmental and social science perspective is essential for sustainable development.
Making an impact
Emma Lucassen (26) is one of those Industrial Ecology students. At least, she was: since October she has been a sustainability adviser at construction company BAM. For her master's thesis, she researched circular solutions for housing construction in Leiden. She followed up on a thesis by former student Marijn Sauer, adds Benjamin Sprecher. He is thesis supervisor and coordinator of the Kennisatelier Duurzaamheid (see text box below). ‘Marijn now works as a circular economy policy adviser at the municipality of Leiden, where she also worked before her master's degree. I think it's great to see that our students end up in places where they can put their academic knowledge on sustainability into practice.’ Because that's what it's all about, says Sprecher: making sure that the right knowledge on sustainability reaches the right people.
Lucassen agrees with this, even more so: it was the main reason she decided to continue studying after graduating in architectural engineering. ‘After studying, I started working at BAM as a work planner, literally standing with my boots in the mud.
Wood lives again
or her master's thesis, Lucassen investigated how the municipality can build enough houses to meet housing demand by 2030, while at the same time reducing the use of materials by half. This involves building some 1,200 new houses per year. ‘I started by determining how much material is needed to build all these houses. I then worked out various scenarios, and assessed which scenario had the highest material savings.’
The scenario with a wooden construction turned out to be the most profitable. With this hybrid form that uses both wood and concrete, the municipality can save more than 40 per cent of the material required, as can be seen in the infographic that Lucassen developed with the municipality. Urban mining, in which materials from old buildings are reused in a high-quality manner, yields 19 per cent savings. Strikingly, a car park under a high-rise building costs almost a quarter of the total material of such a building. ‘The high-rise itself also costs a lot more material than normal construction,’ says Lucassen. 'In theory, you can save up to 35 per cent in building materials by building up to 5 floors, but there isn't enough space in the city for just low-rise buildings. So that scenario simply doesn't work.’ And a wooden facade, what does that yield? Lucassen: ‘Of course it looks beautiful and sustainable, but the profit is disappointing. If you make non-load-bearing building elements, such as the facade and inner walls, from natural materials, that only yields a profit of 7 per cent.’
Lucassen has based the scenarios on techniques that construction companies already apply in practice. ‘Because of my practical background, I know which building methods are currently used. This makes our research results realistic. These results show that the municipality's circular plans are very ambitious, but feasible.’
With our insights, we contribute to better-substantiated choices’
Presenting for aldermen
Lucassen presented her findings during a video meeting to three aldermen of the municipality. ‘That was quite exciting, but fortunately, they were enthusiastic about our research. And it probably helped that I came with a positive message: even if it takes a lot of effort, the goals of the municipality are achievable.’
‘The idea of this project is not only to make an impact but also that the students build on each other's work,’ explains Sprecher. ‘Emma's research shows that more wood is needed for circular construction. But what does this mean for wood production, is there enough wood for this? The next student is going to investigate that. A nice thing to mention is that architect John Heintz of Delft University of Technology is often involved in these theses as a supervisor. In this way, we offer socially relevant research that is also interesting from a scientific point of view and links various areas of expertise.’