Back in 1940, Fritz Leonhardt published an article in the journal Bautechnik entitled “Lightweight Construction – A Requirement for Our Time”. Written against the backdrop of the prevailing economic situation in Germany – a nation experiencing a severe lack of resources following the recent outbreak of war – Leonhardt’s essay examined such topics as mass flows and the availability of raw materials. This discussion led him to issue guidelines for the building industry, resulting in a call for “lightweight construction” that was answered with particular dedication by the Stuttgart school in the decades following the war.
Today, the significance of the developments initiated by Fritz Leonhardt, Frei Otto and others is greater than ever: The increasingly tangible consequences of global population trends, major migratory movements and the exhaustion of material flows pose stark challenges to every single one of us. Handling our limited resources with care is a global problem. Never have we had a greater need for a “lightweight construction for all” that encompasses more fields of enquiry and achieves wider geographical adoption than ever before. As well as striving to create the lightest possible structures, the future of lightweight construction must also be guided by the need to develop recycling-friendly building methods and to minimise the production of grey energy from fossil fuels.
A few reflections can give us the first rough (but entirely adequate) estimates of what the construction industry will have to achieve worldwide in the near future. Around two billion of the 7.7 billion humans alive on our planet today are children and young people (that is, individuals under the age of sixteen). Over the next few years, these children will grow up and will demand their own places to live, their own places to work, and all the infrastructure that goes with it.
If two billion children move away from home over the next 16 years, it follows that we will need to produce a built environment for 125 million people each year. That is equivalent to 1.5 times the entire stock of buildings that currently exists in Germany today. Each German citizen owns approximately 480 tonnes of building materials. If we take this value as a benchmark – and on what grounds should we deny anyone this standard of living?! – we will need to come up with approximately 60 billion tonnes of additional(!) construction materials around the world every single year.
These materials have to be created, transported and used (and disposed of again sooner or later). Sixty billion tonnes of building materials is a hard figure to visualise, so let us illustrate it with a more memorable example: This quantity of material (which, if you recall, is only the amount required per annum!) would be enough to build a 30 cm-thick wall around the equator that would stand at a height of over 2,000 metres.
These figures are unbelievably vast. They provide vivid demonstrations of the scale of the challenges that lie before us. But how can the construction industry help to solve these problems? The answer might be summarised in a single, overarching headline: natura mensura. According to this motto, it is not man (homo mensura), nor a god (deus mensura), but nature that is the measure of all things. Taking this concept as a guide allows us to sketch out the following goals:
- We need to expand the built environment while using less material.
- All construction materials must be incorporated into a recycling process.
- We have to stop emitting gaseous waste into the atmosphere with immediate effect.
Saving energy is deliberately not listed as an objective here, and for good reason: Humanity does not have an energy problem. It is much more important to put a decisive stop to using power from fossil or nuclear sources.
An examination of the relevant material flows has shown that the rocketing demand for an expanded built environment can only be satisfied if we succeed in drastically reducing the amounts of materials we employ. As well as minimising our resource consumption, we also need to make the materials we do use available for reuse at a later date. This means that a “Design for Disassembly” – the production of recycling-friendly constructions and designs – is imperative for two reasons. Firstly, it reduces the volume of new building materials that need to be created. And secondly, it minimises or even eliminates the production of waste that cannot be fed back into the biological or technical materials cycles.
The changes that are necessary to future-proof the building industry can be outlined in just a few words. Nevertheless, we are still a long way from implementing them on a widespread, practical scale. Altering this state of affairs is the great future task that lies ahead of all construction professionals.