Handling resources in the building industry

Our earth’s resources are being used more intensively today than ever before, although it has long been clear that they are often only available now to a limited extent. The building industry has a special role to play here. It is not enough to link the theme of the sustainability of buildings solely to energy efficiency and carbon emissions during operation, which is also the starting point, for example, for the amendment to the German Building Energy Act. An integrated view across the entire life cycle of the building – from the building materials through construction, operation, change of use to dismantling and recycling – is required, because the manufacture of building materials in particular, along with the construction and demolition of buildings consume vast quantities of energy. This is described as grey energy. The proportion of grey energy for buildings is between 40% and 60%, which makes up roughly half of the energy balance of a building throughout its life.

Raw material extraction by the building industry

The construction sector has a major influence on the use of raw materials and thus also on the use of resources worldwide. This means that the building trade plays a key role in the handling of finite raw materials, since at the moment very little use is made of the potential for saving offered by the efficient use of resources.

Considerable quantities of non-renewable resources are used, for example, in the manufacture of building materials required for conventional solid structures, such as cement or concrete. Alongside the extraction of raw materials, the production of building materials also represents a considerable factor in the ecological balance of the building trade. When it comes to sustainability, the safeguarding of resources and protection of the climate, it will therefore become ever more important in the building industry to keep existing materials increasingly within material cycles and to reuse them as often as possible without any loss of quality.

Urban mining and recycling-oriented building

hen planning a building, its demolition is generally not yet taken into account. The idea of building for eternity still prevails, but demolition is often a reality and uses vast quantities of energy, generally leading at the moment to a massive waste of resources.

According to information from the Federal Statistics Office, in 2020 in Germany alone, for example, around 198 million tonnes of building and demolition waste were produced by the building sector, corresponding to 55% of all German waste materials. This is where the idea of urban mining comes into play. This means the recovery of reusable or recyclable building materials and components from buildings that were not designed or built with the concept of recycling in mind. In Germany, almost 90% of building and demolition waste is already being reused as a sort of anthropogenic raw material store.

However, the problem is that this waste is generally downcycled. This is the term for the further utilisation and recycling of used building components or building materials where there is some loss of quality – if concrete is shredded and then used as a filler in road building, for example. In this respect, the building industry is still far from a circular economy, which is defined as being a self-recovering and self-renewing system that aims to maintain the highest possible quality of its materials and products in enclosed material cycles.

Where does modular construction stand in relation to recycling-oriented building?

Steel modular buildings match the concept of a building designed with foresight and planned intelligently in terms of the materials cycle.  They stand out among permanent buildings as being “mobile real estate”. With steel modular construction, it is possible to demolish buildings by dismantling them into their individual modules, then to transport these to another location and reassemble them there. The basic steel structure means that it is possible to give the buildings a new life in this way.

Modular buildings thus embody the principle, way beyond the concept of urban mining, of recycling and even reusing. Reuse is the term used if a material or component is used again 1:1 in a further utilisation phase. This is the case when a steel modular building is dismantled and reassembled without any changes at a different location.

Generally, however, it is the principle of recycling that applies for modular buildings. In contrast to reuse, the building is adapted for a new requirement, e.g. by changing the floor plan or the technical building equipment, or to bring it into line with new overall building regulations.

What makes modular buildings so flexible to use and thus so sustainable?

The reason why a building in the ALHO system can be easily relocated is its self-supporting steel frame structure with non-loadbearing walls. This allows the modular buildings to be flexibly adapted to changing requirements and adaptive reuses by changing the floor plan. Walls can be moved or opened up, storeys and extensions can be added easily and quickly. To this extent, the modular construction system is extremely flexible and very suitable for later alterations and changes of use. This type of adaptive reuse often happens when the building stays in the same place. This ability to change the use of a building is an important feature for assessing sustainability according to DGNB and BNB requirements.

The ALHO modular construction method is based on three-dimensional structures made up of individual steel modules. These are joined to each other mechanically and can be separated again. Because of the double-shell structure of the supports, floors and ceilings, it is easy to dismantle the building into its individual modules once the welded joints are loosened. Consequently, complete conversion, partial conversion or reassembly of a building’s modules are all possible. All the installations required for a room are pre-installed in the individual modules at the factory and then connected to the mains services on site. They can be separated off again just as easily for dismantling, e.g. using plug connections for electrics. Because the buildings have generally been used for many years in one location before being moved to another, reconstruction measures are often required for any new use, resultant alterations or extensions to rooms or technical upgrades due to changes in laws and standards.

These can easily be carried out either after dismantling, during interim storage at a processing site, or after reassembly at the new location, largely without any additional work on the bearing structure and thus without affecting the structural load calculations. Because a change in a building’s location usually involves meeting new customer requirements and the latest statutory regulations also need to be taken into account, one-to-one reuse is almost impossible in practice. But by recycling a modular building with a high proportion of reuse of the building materials, especially the steel structure, modular construction is setting new standards in terms of sustainability and the efficient use of resources in the building industry.