Materiality in Flux – Roger Boltshauser
The practice of building with earth dates back millennia, and in many places today, research is being conducted into contemporary techniques for utilizing this time-honored tradition. In this issue, Roger Boltshauser and his team at ETH Zurich document their approach to current issues surrounding earthen construction. We are interested in gaining an insider’s view of their think tank and hands-on workshop. We are aware that earthen construction is also being researched and practiced elsewhere in Europe: for example, in Austria, Germany, Belgium, and for a long time now, in France. Between 2004 and 2008, Roger Boltshauser engaged intensively with earth as a building material when designing and constructing a new residence for Martin Rauch. Boltshauser, who began lecturing at ETH Zurich in 2018, became a full professor of architecture and regenerative building materials in 2024. In light of climate change and the increasingly hot summer months in this country, the building physics properties of earth construction are of great interest. These properties include thermal storage mass and absorption capacity. Another advantage is the ability to reduce the amount of technology required for construction, making it possible to achieve a good indoor climate while significantly reducing CO2 emissions. Earthen materials, particularly loam, also have excellent soundproofing and fire safety properties. In addition, loam with an appropriate composition ratio is often available locally. Depending on its quality, however, sand or clay may need to be added to improve its load-bearing capacity. While this building material is a finite resource, it can in large part be returned repeatedly to the resource cycle and is interesting not least from both ecological and economic points of view.
Using earth is only a starting point – and the ideal is not always achieved. These issues challenge us to question and rethink our aesthetic beliefs and our expectations of comfort, which have almost become second nature.
New products can only be created from reclaimed building materials in a resource-efficient manner if they can be returned to the loop in sorted, pure form after they reach the end of their service life. This inescapably looks different, too. A changing understanding of what good architecture means for our environment and all of us – and our and need for it – is leading to a new aesthetic. Loam also has an added benefit: Because its ecological balance is much more advantageous but its load-bearing capacity is worse than that of concrete, designers must (once again) focus more on structure and tectonics. We are all called upon to distinguish more thoroughly between what is conceivable and what is livable, and to begin to surrender, at least to some extent, our strong resistance to the long-overdue and urgently necessary structural transformation.
Today, the term “hybrid construction” is used inconsistently. On the one hand, it can refer to components in which heterogeneous materials are inseparably joined and which cannot be separated into distinct materials later on. On the other hand, it can refer to a mutually beneficial combination of various materials that perform better together and can later be easily separated later on. This results in a better ecological balance and a more sustainable material cycle. This captures the interest of Roger Bolthauser and his team in both research and practice.
The Editors