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GXN: 'In addition to wood, we continue to need concrete, but we need a different kind of concrete’

30 November 2023

During Architect@Work Amsterdam, the Netherlands, architects Aleksander Kongshaug (GXN) and Christian Veddeler (3XN) delivered a lecture about the next steps in circular and bio-based construction. Architectenweb spoke briefly to Kongshaug about what he is currently focusing on at GXN.


© Adam Mørk


“With GXN we are conducting research designed on a scale where we can make that happen,” begins architect Aleksander Kongshaug of GXN. “If it works on that smaller scale, it can also be applied on a larger scale at 3XN later.”


An example he mentions is the all-wood wing of a hotel they designed in Denmark. Twenty-four hotel rooms with a supporting structure made of cross laminated timber (CLT) and Glulam, wood fibre insulation and wooden cladding. The extra step they took was to use the cutouts in the CLT panels, for example for the doors, to make tables for the hotel rooms.


© Adam Mørk


In the next project, in Brussels, GXN is now looking at the cutouts and other residual material from the European wood industry that it can use to build a larger project. In this way, waste is used as a building material.


Is building with wood ultimately the future? “It is not the solution for everything,” Kongshaug indicates. “Especially in larger and taller buildings, a completely wooden construction has its limitations, and a hybrid construction works better, for example with a new base and a wooden structure.”


© Hampus Berndtson


© Hampus Berndtson


To another concrete

“Although saying goodbye to the concrete industry would largely reduce the impact of construction on our planet, it is not possible to contemplate a world without it just yet,” says Kongshaug. “We can use less concrete and, in collaboration with the concrete industry, continue to insist on making the material more sustainable.”


“Smart, modular construction is another sustainable process whereby building elements can be taken apart again and separated,” he continues. “We are regularly involved in projects that involve the demolition of building elements that are less than thirty years old. There is nothing wrong with these elements themselves, it’s just the buildings they come from can’t be adapted to new demands from the real estate market and society as a whole. Some of these elements are very large and cannot simply be removed in a straightforward way. That's why everything gets demolished. By including the option of installation in the design, we can make concrete structures adaptable and therefore future proof them.


“At the same time, we also have to investigate whether we can make concrete in a different way, for example by using bacteria,” says Kongshaug. “Biomason, a firm from the United States, has developed a process in which bacteria can make a form of sandstone. The company is also able to make a kind of lightweight concrete with the same bacteria. Last year, we discovered how that process can be scaled up: how we can make columns with that material. For example, in 72 hours, a material was created that is 20% lighter than concrete, but also three times stronger. This is a new kind of concrete, but without high CO2 emissions.”


Bio-based building materials

In recent years, GXN has conducted research into all kinds of biobased materials. In collaboration with an agricultural trade body in Denmark, it has developed a modular construction system that uses waste ingredients, such as the stems of tomato plants, seagrass, wood fibres and seaweed.


© 3XN / GXN


Recently, Kongshaug has mostly been looking at existing building structures and examining how certain elements can be reused in the new building. And if that is not possible, how can we ensure that the materials are reused?


© 3XN / GXN


In Copenhagen, GXN is located under the same roof as 3XN and works as the R&D arm of the studio. From a business perspective, however, it is completely independent. About half of the design research is carried out on behalf of the public sector, the other half is done for commercial clients. About twenty research designers work at GXN, because it is always about research that can be applied immediately. Says Kongshaug finally, “We always put it into practice.”


Originally written by Michiel van Raaij 


GXN: 'In addition to wood, we continue to need concrete, but we need a different kind of concrete’
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