Energy-efficient and CO2-neutral: How will we build in the future?

While the whole world is talking about climate protection through electric cars, the building industry is rarely discussed as a "climate killer". You are probably aware of a few aspects of ecologically sustainable buildings, such as good insulation, intelligent energy management and solar panels to heat water. But more than half of the total energy ever used to build a house is consumed by the time it is finished. That's why in this article we draw your attention to the less common aspects of environmentally sustainable buildings, such as the right choice of materials.

To put it in a nutshell: The current way of building will not work for much longer. The following facts illustrate why this is so:
- In Germany, 90 % of the total domestic extraction of mineral raw materials is used in the construction sector. This corresponds to about 517 million tonnes annually.
- Every year, 5.5 million tonnes of construction steel and 26.6 million tonnes of cement are used in this country. Both are extremely energy-intensive and high in emissions in their production. Around 8 % of CO2 emissions worldwide are due to the production of cement, for example.
- More than half of our waste comes from the construction industry: 209 million tonnes of demolition waste have to be disposed of every year.
- In industrialised countries, the operation of buildings consumes between 30 and 40 % of the total national energy.

You can see that the building sector is very resource-intensive at the moment. The current way of building in our country is mostly unsustainable. The resulting emissions alone are many times higher than the maximum level that would still allow us to comply with the Paris Climate Agreement. The way most building sites look at the moment, instead of a maximum of 2 °C, global warming of 6 to 8 °C is more likely.

In addition, some resources are simply limited. Sand, for example, is already in short supply on the world market, and in Germany there is also a shortage of gravel. The situation will be similar for materials based on mineral oil in the future, although these should also be discontinued as soon as possible for reasons of environmentally friendly disposal.

The good news is: More and more people want to stay in sustainable buildings. A healthy indoor climate through natural materials is worth it to them to invest more in construction. In the end, the building costs may well pay for themselves through lower operating costs.

Before we talk about the principles of sustainable building, we would like to state briefly: In the vast majority of cases, renovation makes more sense than new construction. Since a large part of the material, emissions and energy is generated during construction, the continued use of existing properties is the order of the day. This also eliminates the need to develop a new area and thus seal a piece of nature. In some cases, however, there is no other option than to build anew. Then, for the sake of sustainability, the following criteria must be taken into account:

- Minimise resource consumption
- Minimise land consumption
- strive for the lowest possible environmental impact during construction, use and deconstruction
- Do not neglect pleasant living atmosphere and appealing design

Even though these points are easy to address, their implementation is still problematic when planning new buildings. On the one hand, this may be due to the habitual thought patterns of architects and builders. On the other hand, the strict German safety regulations as well as the ubiquitous DIN standards make the establishment of innovative materials and sustainable designs complicated.

In terms of resource consumption, one idea has already established itself: energy efficiency. Here, ideas range from sophisticated thermal insulation to self-sufficiency in electricity and hot water through solar energy. In this context, people unfortunately overlook far too easily that highly developed technologies consume enormous resources in their production. Here, in future, builders must rely on rigorously thought-out solutions that put the energy efficiency of a property in relation to the consumption of energy during construction. Added to this is the intelligent use of building materials, which on the one hand should come from recycling wherever possible and on the other hand must themselves be able to be disposed of or reused later in an environmentally friendly manner.

Ultimately, the aspect of sustainability must be taken into account in the entire building industry. It is not enough to design building construction ecologically. This is where urban planners come in and take care of the development of an appropriate infrastructure. Exemplary projects such as Lokstadt in Winterthur or Le Central in Düsseldorf vividly show how the design of the entire living space promotes environmentally friendly behaviour among residents. Here, particular attention should be paid to the arrangement of living, working and leisure space, the accessibility of shopping markets and the design of routes. If all the necessities of everyday life are close to the home, a car becomes superfluous. Preferential use of footpaths and cycle paths instead of roads and the expansion of public transport do the rest.

It is difficult to make a general statement about which material is suitable for sustainable building. On the one hand, the aspect of regionality plays a major role. The shorter the transport routes, the more ecological the corresponding raw materials are. On the other hand, research is constantly developing new technologies and processing possibilities for raw materials that reduce the ecological footprint of a new building. At this point, we can only offer you a few examples of sustainable resources on German construction sites:

In the past, people inevitably used as building materials the things that were in the immediate vicinity of the construction site. In Germany, for example, these were wood, straw, clay or natural stone. This resulted in perfectly acceptable dwellings that achieved a long half-life, as many a half-timbered house still vividly demonstrates today. In addition to the aspect of regionality, it is important that the raw material is obtained without damaging the environment and is used in as natural a way as possible. In the case of wood, this means that it must come from sustainable forestry and must not be treated with chemicals.

So far, the trend has been to invent ever more complicated composite materials that provide ideal conditions in the finished house. These include, for example, so-called phase change materials for insulation. They alternate between solid and liquid states and can thus absorb excess heat or release it again. The problem with such materials, apart from their energy-intensive production, is their subsequent disposal. A solid compound of different raw materials is usually a case for hazardous waste. Therefore, in the context of ecological sustainability, the focus must be on compounds made exclusively of biodegradable composites. In addition to wood, for example, minerals, calcium or hemp fibre can also be used as raw materials. All these raw materials are stable, flexible, durable and easy to process.

An ideal in the sky of sustainability is the self-sufficient house. This means that it is not dependent on any energy from outside, but can supply itself. It produces its own electricity from the sun, wind, geothermal energy or whatever is available on site. To get by with as little energy as possible, the green buildings of the future must be smart. Sophisticated technology will control the home to be as energy efficient as possible while accommodating all the needs of the occupants. The perfection of this idea is probably the so-called "Eartships". They are not only energy independent, but also have their own closed water circuit.

The current way of building houses pollutes the climate and the environment. The demand for raw materials is enormous. In addition, the energy consumption and emissions are so high that a climate goal, as stated in the Paris Agreement, is hardly achievable. Ecologically sustainable construction mainly uses regional raw materials that are sustainably obtained. They must be easy to recycle or biodegradable, such as wood. The sustainable house itself is energy-efficient, at best even self-sufficient. In addition to building construction, the ecologically sensible design of localities or urban districts is also a central aspect in terms of sustainability. Environmental friendliness and quality of life should have a high priority here.