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Precast concrete buildings given a new life by Helsinki hackers

Updated: Jan 7, 2022

By Jenni Nieminen

Between the 1960s and 1980s, precast concrete buildings were all the rage in Finland. But now they’re causing a problem: many of them are being demolished and will continue to be demolished over the coming years and decades – and the figures for construction waste are already sizeable in Finland, with 1.6 million tonnes of construction and demolition waste produced every year (most of which is concrete and stone).

As our goal here in Finland is to apply circular economy principles to all stages of a building’s lifecycle, it’s essential that we find new ways to reuse building components from these concrete houses as we tackle the climate impacts of concrete production and disposal. And whatever the solutions we develop, they have to be replicable and scalable, not least because of the sheer number of these kinds of houses across the country.

So one of our CIRCuIT partners in Finland, HSY, along with the Ministry of the Environment of Finland, the HYPPY project and real estate company Hämeenlinnan asunnot Oy, recently put a challenge to 28 higher education students from six universities in a series of three hackathons. The challenge we set them was to develop new ideas for reusing concrete building components.

Split into seven teams, the participants (made up mostly of senior students in the built environment) were given a real building, owned by real estate company Hämeenlinnan asunnot Oy, to consider when developing their solutions. The building was representative of an often-demolished apartment building type in Finland.

The virtual hackathons kicked off with briefings from the CIRCuIT Helsinki region partners and other circular construction experts, who worked with the teams to challenge and support them throughout the day.

The task of finding new ways to reuse building components remained the same in all three hackathons, but each one tackled a different part of the process:

· The first hackathon focused on innovations, with participants brainstorming and defining a variety of circular possibilities. Each team came up with multiple ideas that varied from repurposing concrete slabs to deconstructing different building parts to ensure they can be reused. At the end of the hackathon each team chose their best idea to develop further.

· The second hackathon focused on turning the chosen ideas into a product. The teams examined the technical feasibility and value proposition of their ideas, using process charts to structure their ideas further.

· In the third and final hackathon, the teams looked at how scalable and practical their circular innovations were – could they be implemented widely? And what more development was needed to turn their ideas into reality?

The whole series then culminated in a public event, where each team pitched their ideas to a jury made up of experts in architecture, structural design and circular construction. The jury evaluated the ideas against criteria including environmental benefits (especially carbon dioxide savings); feasibility, scalability and cost-effectiveness; how innovative the ideas were; and last but not least, the architectural quality and aesthetics of the product proposed.

Re-imagining precast concrete

And the winner was… “Loft upcycled”, developed by three Aalto University students: Saara Kemppainen, Heljä Nieminen and Havu Järvelä. Their proposal was to reclaim load-bearing interior walls and precast flooring slabs and use them to build a loft-style house – an idea which is particularly powerful as these components form 52% of the carbon footprint of the original building. In contrast, when the new house is built from recycled concrete partition walls and floors, its carbon footprint is actually smaller than that of a newly built wooden building.

The concept is technically robust as it makes use of standard elements of equal size: the elements are fixed on top of each other to form a high wall using detachable mechanical joints. A loft inside the flat makes the solution transformable and flexible; and the idea even included a plan for a quality certificate for disassembled building parts.

According to a member of the jury and post-doctoral researcher, Tapio Kaasalainen from Tampere University: “The winning proposal examines the potential for scalability in the building stock with distinction. The journey from dismantling the old to creating the new building, with all its complex challenges, is well considered. All in all, the proposal is very clear and comprehensively planned.”

The winning team’s idea: “Loft upcycled” by Saara Kemppainen, Heljä Nieminen and Havu Järvelä from Aalto University

Second place in the hackathons was shared between two teams: both ideas, Q-Haus and BlockBox, were based on the same principle of modular units made of the concrete slabs that would be disassembled from the precast concrete building. The two teams presented slightly different approaches on how the modular units would be used. The Q-haus solution was for use in housing; whereas BlockBox was mainly intended to be used in garages and other non-residential buildings.

Second place: Q-Haus (Eevi Lindroth, Elina Kauranen, Elina Dobrzhanskiy, Anni Marttinen and Taru Karnaattu from Tampere University)

Second place: BlockBox (Suvi Rantamäki from Aalto University, Veera Saastamoinen from Tampere University, and Arttu Nikula, Pekka Natunen and Ville Saastamoinen from Häme University of Applied Sciences)

The remaining four teams presented some really interesting ideas including material exchange platforms for reused building parts and stackable, Lego-style element solutions. All the teams tackled the challenge with innovation, energy and insight, with all of the ideas giving the CIRCuIT team food for thought. The challenge of how to reuse building components from precast concrete buildings is current and real, and we need scalable solutions right now.

The winning ideas are currently undergoing further review by property company, Hämeenlinnan Asunnot Oy and CIRCuIT is actively seeking opportunities to implement the ideas in real life.

How can you get involved?

If you are a property company that is interested in hearing more or have any questions please get in touch at

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