Wood, clay and straw: good for the climate

27 August 2020

Everyone knows that there’s no good alternative to a roof over your head. However, the way buildings are currently constructed and operated is extremely harmful to the environment. Something that the “Architects for Future” are keen to change. This free association of architects and civil engineers is committed to an ecological rethink in the construction industry. We talked to civil engineer Tore Waldhausen about why refurbishment is better than building from scratch and how wood and clay can be good for the climate, both in our homes and around the world.


#explore: What makes construction so harmful to the environment, Mr Waldhausen?

Tore Waldhausen: Construction is associated with the consumption of immense amounts of resources. 50 percent of the world's energy and 50 percent of the resources mined are used in the construction and operation of buildings. And that’s not all: a lot of ground is sealed by buildings, roads and car parks. And while a lot is already happening in terms of energy saving in building operation, the public is often unaware of how much energy gets used in construction and the production of materials.


What are the central goals and demands of “Architects for Future”?

One of our main demands is to take a fresh critical look at demolition. A lot of buildings get demolished because it’s often cheaper that way. From an ecological point of view, however, it would make more sense to continue to use the existing substance to avoid having to sink new energy into new materials. We’re also calling for the use of healthy, climate-friendly building materials. A very important point here is the adoption of the circular economy in construction. We should choose and develop materials and products in such a way that we can continue to use them in closed cycles in a way that prevents them from becoming waste in the first place. And this is where the next point comes in: we need to avoid downcycling. Although materials are often already recycled on construction sites, their quality and functionality usually deteriorate. This is then officially referred to as recycling, even though these building materials gradually lose their value. We also want to use urban mines: in other words, to use the existing substance as a matter of priority. Last but not least, we’re also concerned with preserving and creating biodiverse habitats – for example, with green roofs and green facades in urban environments. We basically want construction to play a part in creating an open society. We spend 90 percent of our lives indoors. For this reason, architecture has a huge influence on how we live together.


What might this kind of circular system look like in the construction industry?

We’re strongly influenced by what’s known as the cradle-to-cradle principle. Transferring this idea to construction, this means that we think in terms of two different cycles: one technical and one biological. One example of a biological cycle would be the use of wood as a building material. When it’s properly used in construction, wood has a very long service life. If it has to be removed and taken apart, then there’s a long chain of other uses: It can be used as a chair, then as wood-fibre insulation board and, finally, as fuel. If it hasn’t been chemically treated, it can also be composted. Then it becomes a nutrient for woodlands or benefits the soil in other ways. In a similar way, we also have to design technical materials in such a way that they get reintroduced into the cycle as a “nutrient”. For example, if steel is used in construction in such a way that it is separable from all the other materials, it can then either be reused directly or melted down to produce new steel. This assumes, of course, that we can develop methods to produce or process steel exclusively with renewable energy.


Why do we need alternatives to cement and concrete in the first place?

Cement and concrete are incredibly practical building materials with a lot of applications. But there’s a major problem here: during production, enormous amounts of CO2 are released. Cement production is responsible for four to eight percent of global CO2 emissions – more than global aviation. Climate-friendly building materials offer enormous savings potential here. In some areas of application - tunnelling, for instance - there’s still no suitable alternative to concrete. Here we need to continue researching into alternatives. But especially in housing construction, where the structural engineering requirements are less stringent, there are some very good substitutes in the form of wood, clay and straw, which, if used properly, will also benefit the health of the residents.


What are the advantages of wood, clay and straw for the environment and residents?

Wood is a natural CO2 storage system. And every kilo of CO2 stored is currently worth its weight in gold. Wood also has good thermal insulation properties and is breathable. In other words, it’s really good for the internal climate. The same applies to clay, which has temperature- and moisture-regulating properties. Spending time in an indoor space made of, or clad in, clay is simply a very pleasant experience. Clay has even better credentials than wood as a regional product which doesn’t have to be transported over long distances. Straw, in turn, has wonderful insulation properties and is a natural raw material. It only has to be compacted and can be delivered directly to construction sites by the farmers from the region. Straw walls can be easily plastered with clay. Combining these two gives rise to a wonderful indoor climate.


When it comes to straw buildings, the layman might be forgiven for thinking of the fairy tale of the three little pigs, in which the evil wolf razes a straw house to the ground in no time. How strong and fire-resistant are straw buildings?

Just adding a layer of clay cladding guarantees basic fire safety and also ensures that vermin will not eat the straw. Building a straw house in a city is a bit more difficult at the moment. According to fire safety regulations, a building must be able to burn for sixty to ninety minutes without collapsing. Ensuring that straw meets this requirement is challenging, but possible. In structural engineering terms, a straw house must of course meet the same requirements as any other house. In Germany, such houses are mostly built with a wooden frame, and the straw is only pressed in as thermal insulation. Even using straw in load-bearing walls, for example in a semi-detached house, wouldn’t technically be a problem, but this isn’t yet allowed in this country. There’s currently a move to adapt building regulations to allow its use.


Are such materials suitable for all building types and regions?

Yes, absolutely. In some cases, there’s even a compelling physical case for their use. The building structure is more flexible than it would be with steel or concrete, which means that it would cope better with the requirements of an earthquake region, for example. Bridges for heavy goods traffic are now also being built from wood, for example in the Netherlands. In Norway they’ve built an 85-metre wooden skyscraper; in Japan, a 350-metre wooden skyscraper is planned. Such projects attract attention and will help to ensure that wood is used in a wide variety of contexts. This has to be a good thing. However, when it comes to meeting the growing demand in cities, we don’t necessarily have to build new high-rise buildings. Depending on the structure of the building, one or two floors can be added to residential buildings – this is often seen in Vienna. In this way, new living space is created without sealing any further space. We can also implement such concepts with the kinds of alternative building materials we’ve been talking about, and we should also adopt a much more consistent strategy to that effect here in this country.


Investors often just find green construction too expensive. How can we change this?

Investors and builders often think too short-term. And yet, ecological construction is always also high-quality construction. It may require a little more investment at first but is more durable and holds its value better. Such a building can be passed on to the next generation in 50 years’ time or resold without any loss of value. This is because the building materials are circulated in closed cycles, meaning that they don’t lose value throughout their service life. In other words, green construction can already be worthwhile today. For the environment, for the residents, but also for the investors.


Which political course must be set to promote sustainable construction?

The most important measure would be to make the CO2 emissions released in the production of the materials and in the construction process more costly. Refurbishment would then become more economical than demolition and building from scratch. At the same time, this would also do wonders for the demand for and availability of renewable building materials. To make renovations more attractive, a possible option would be to introduce mandatory approval processes, like those associated with construction, for the demolition of buildings. This could include mandatory decommissioning plans. The aim must be to share responsibility for disposal more fully with the manufacturers.


What role does sustainable construction play in studies and training?

Far too small a role, sadly! The German Society for Sustainable Building has got things moving in recent years, creating various modules and seminars for architectural training. But the programmes on offer at universities and for the training of craftsmen are still very limited. For this reason, many students are turning to our regional groups to find out more about circular construction using clay or straw. Some early developments are currently underway to encourage more universities to offer courses in climate-friendly construction. But there's still a great deal to do here. We at “Architects for Future” are therefore trying to ensure that this need on the part of the students is actually met.


How do you at “Architects for Future” intend to advance the sustainability agenda in construction?

In my view, the concept of sustainability falls a little short, because it suggests that it’s only a matter of making our negative carbon footprint a little smaller. Instead, our buildings could actually leave a positive footprint and benefit people and the environment. At "Architects for Future", we want to use public relations and educational work to educate people about the possibilities of this kind of climate-friendly construction method. At the same time, we’re also directly involved in politics in that we’re contributing our expertise, for example, to urban construction projects.


"With its green facade, the town hall in Venlo been shown to cleanse the air within a radius of 500 metres."

Tore Waldhausen, spokesman “Architects for Future”

Which projects have already implemented this kind of climate-friendly construction and could set an example to others?

Anyone who’s trying to build differently and better is already making an important contribution! In my view, the town hall in Venlo in the Netherlands has set the benchmark in terms of specific construction projects. With its green facade, it’s been shown to cleanse the air within a radius of 500 metres. And it’s having a positive impact on the health of the employees, who take less time off sick than other people in comparable jobs. Moreover, a lot of cradle-to-cradle-certified materials have been used in this building. And it’s especially significant that the initiators have attached a great deal of importance to bringing together all those involved in the construction from the very beginning to jointly create a building that provides positive added value for the region. In conventional projects, you all too often find that all those involved are working against one another. The town hall in Venlo is a great example of how you can build differently and better if everyone pulls together.


What does the ideal sustainable building of the future look like for you?

Houses that look like trees, cities that look like forests – that's how I’d describe my vision: How would it be if our houses were to store CO2 like trees? If they improved air quality and were powered exclusively by renewable energy? If our buildings used local resources which were circulated in closed cycles and were home to a lot of different people and living beings? We can and should increasingly put these principles into practice in specific buildings.


Tore Waldhausen is a civil engineer and spokesman for “Architects for Future” in Leipzig. He focuses mainly on ecological construction methods and building renovations. Waldhausen is currently involved in a construction project near Bamberg, in which a climate-friendly residential development based on circular economic principles is to be built for around 100 people.