Glossary

Preface

This Digital Construction Theory is intended as a bridge between the established fundamentals of construction and the dynamic possibilities of digital tools that shape our design and planning processes today. While classical construction principles continue to form the foundation of architectural design, increasing digitalisation opens up new ways of understanding and visualising constructive relationships.

This work is designed to offer orientation to both architecture students and practitioners alike. It conveys fundamental methods of construction, demonstrates work processes, and places their practical application at the centre. Interactive models, simulations, and comprehensible examples support the intuitive experience of complex content.

The Digital Construction Theory is conceived as a living document: it grows with the progress of technology and research and is intended to evolve. In doing so, it invites you to sharpen your own constructive thinking, to boldly try out new paths, and to responsibly contribute to a sustainable construction industry.

The Digital Construction Theory aims to awaken curiosity, foster creativity, and strengthen the joy of developing sustainable solutions.

Digital Construction Theory

Costruire correttamente – in English "building correctly" – is the title of a book by Pier Luigi Nervi, that designer who brought architecture and engineering together in his projects like few others. "Building correctly" could also be the motto of the Institute of Constructive Design (IKE), not least because "correct" refers not only to material efficiency – and thus the sustainability of structures – but also to the activity itself. "Building correctly" also concerns the social and ethical dimensions of architecture. Construction brings structure, tectonics, space, material, and materiality together in expression. A construction is "correct" when it refers to these aspects and meets all requirements – which is becoming increasingly demanding today, not least because of the complexity of building and the tightness of the normative corset. Construction theory is thus the place where engineering and architectural knowledge come together and experience a synthesis. It is the place where one learns to construct "correctly". But it is also the place where one learns those techniques with which one can create projects – "worlds" – and thus architecture.

Construction is always conditioned by the economy – including the economy of means – and therefore relies on proven systems. Over the last sixty years, these have been repeatedly "disrupted" by various crises – above all the oil price crises of 1973 and 1979/80 – and have had to adapt. This led, for example, to double-leaf masonry and ventilated facades in the 1980s or increased insulation for Minergie in the 1990s. In the sign of the climate crisis, a new engagement with construction has developed in recent years, which no longer recognises it as a monolithic system, but as a sum of parts, each of which has specific tasks to fulfil. Hybrid systems made of steel, concrete, timber, and earth (other regenerative materials are also suitable here) show themselves to be promising, as they react differently to requirements and combine different qualities intelligently. This also means questioning contemporary narratives: concrete is not bad per se and timber good per se; it is necessary to differentiate here and consider the wider context, right up to the availability of materials and their cycles.

In this context, the reuse of building components is gaining importance, with all the difficulties and challenges that entails. However, this is not something new, as the book Bauteile wiederverwenden (Reuse Components), published by IKE (Park Books, 2019), has shown. The periodic "necessity" for architecture to reinvent itself manifests itself not only in the rediscovery of "old hats", but also in the fact that knowledge is lost and must be regained. The use of regenerative materials or the building of solar-active or passive houses also naturally has a very long tradition to which we must refer.

Since the separation of design and execution, which was carried out by architects in the Renaissance in the name of ennobling their profession, the question has repeatedly arisen as to how knowledge of execution and corresponding planning can be conveyed. As long as building was based on traditional materials and constructions, the transfer of knowledge presented less of a challenge and could be acquired through classical construction theory at academies and architecture schools as well as through the supervision of construction sites. With the increase in the complexity of building as a result of industrialisation and the emergence of new materials and processes, the need for corresponding literature and instructions arose more and more.

There are countless books on building materials, structures, and/or construction and building technology; hardly any architect has not dealt with these topics more or less intensively. The publication Elementare Bücher zum konstruktiven Entwerfen (Elementary Books on Constructive Design), published by IKE in 2018, provides an overview of the most important literature. The success of Ernst Neufert's Bauordnungslehre, first published in 1943, which deals with construction only marginally, shows the desire for a certain systematisation of knowledge. The Manuale dell’architetto (1946), published shortly afterwards in Italy, testifies to the need for a dissemination of rational construction methods.

This type of transmission was very helpful, but also had a standardising effect, as it offered little room for creative exceptions and also the atmospheric character of the construction. The latter is primarily the subject of the hitherto unsurpassed Architektur konstruieren (Constructing Architecture). A handbook by Andrea Deplazes and his chair team, which was first published in 2005, has since been reprinted several times and translated into countless languages. The numerous translations testify to the great interest in a construction theory "Made in Switzerland", because here execution down to the smallest detail has a long tradition that is still lived today.

Why digital? Basically, as an institute, we are critical of digitalisation in the construction industry, not least because although it makes new applications available to architects, these are hardly changeable as closed systems. Such applications can sometimes optimise processes, but often have a drastic effect. Since quality can hardly be translated into parameters, architecture is thus reduced to a question of quantities. This is particularly evident in the new AI-supported tools. Building Information Modelling (BIM) also undoubtedly brings rationalisation gains, but at the same time pushes for a shortening of the concept phase, and changes are difficult to incorporate because the digital model is seen as "absolute".

From our point of view, this calls on architects to engage more strongly with this technology and makes it necessary to develop their own digital applications.

The Digital Construction Theory is indeed also built on parameters and data, but these are only the basis for an in-depth engagement with exemplary projects that can be examined in detail. This takes place via three-dimensional and animated models that offer themselves to a dynamic viewing. It is important that one remains aware of the high abstraction of digital space and that there is always feedback in "real" space, be it through drawings or models. Thus, the Digital Construction Theory should offer precisely that openness which we often miss in contemporary digital tools.

With the climate crisis, not only construction and the way it is viewed have changed, but also the way it is conveyed. This now happens not only via drawings, dimensions, and tolerances, but also via Life Cycle Assessment and thus primarily via numbers. It is precisely here that digitalisation offers great potential, since, for example, the automatic link with the KBOB list allows these numbers to flow into the constructions and thus relates them to architectural qualities. That these are not exact values, but merely approximations, should be clear to everyone, since this is, after all, a design tool.

A further advantage of the Digital Construction Theory is that it can be further developed and also improved by new constructions and extensions coming from research. It is thus not just a static snapshot, but a constantly growing instrument.

It should also be emphasised that the Digital Construction Theory emerged from the Workpiece Hall of the Institute of Constructive Design at the ZHAW. The 1:1 mock-ups of hybrid and climate-appropriate ceiling constructions, which are exhibited and researched in the Workpiece Hall, were the starting point for those first constructions that were included in the digital collection of construction types. Accordingly, there is a connection via these to "Halle 180+ Raum für Wissen" (https://wissen.halle180plus.zhaw.ch/index), the digital archive of the Department of Architecture, Design and Civil Engineering at the ZHAW.

In the end, it only remains for us to express a big thank you: to the architects and clients who granted us access to their projects, as well as to everyone who participated in the development of the Digital Construction Theory. We hope to have made a contribution to a more sustainable way of constructing with this tool, which integrates the perspective of architects more strongly.

Standards

Why is something done in a certain way at a certain time in a certain place and not otherwise? In his work, Michel Foucault focuses on this actual doing of people. He refers to it as practice. According to his observation, this human making is neither particularly purpose-oriented nor intentional – and far less shaped by great ideas, ideals, or ideologies than we might think. In Foucault, the concept of practice becomes the pivot of a fundamentally new conception of history, which the ancient historian Paul Veyne calls "revolutionary" (Paul Veyne, Foucault révolutionne l’histoire, Paris 1978; as an example of a particularly long-lived practice, he describes the history of Roman gladiatorial combat). If we refer to Foucault and take up the concept of practice, other phenomena that defy decoding at first glance may become somewhat more tangible.

If we concern ourselves, for example, with the question of how the local construction industry is reacting to the demands of climate change, we may be somewhat perplexed. As is well known, the building sector accounts for a large share of the CO2 balance. In view of this, the practices of the construction industry appear astonishingly resistant to the claims for control and change in society vehemently represented in the media. To achieve climate goals, the reduction of greenhouse gas emissions to net zero by 2050 has been enshrined in law in Switzerland. The Paris Agreement, with which Switzerland committed itself to this goal, was ratified in 2017. Has anything decisive changed in the construction industry since then? Sustainability as a term is indeed omnipresent in the everyday life of the building industry. But whatever is neither prescribed by the authorities nor required to achieve any labels has a hard time. The processes, the practices of building, are apparently too ingrained.

Central to the regulation of the Swiss building and planning system are the national rules of the building art, known as SIA standards. In Switzerland, they are not developed and issued by the state, but by a professional association, specifically the responsible bodies of the Swiss Society of Engineers and Architects (SIA). They are categorised into technical standards, contractual standards, and understanding standards. The technical standards represent the collectively accepted state of the art in construction. SIA standards are not considered laws. Only through contractual agreements do the private standards of the SIA become legally binding according to the Code of Obligations. In this way, they acquire a quasi-legal claim in practice, which is supported by the courts in legal cases. In many cases, SIA standards are also the basis of laws passed by parliaments.

Consequently, there is a broad social consensus that compliance with SIA standards is essential for the safety of buildings and facilities, for functionality, durability, and economic efficiency, in short: for the quality of structures. The SIA, as the most powerful professional association for planners in the construction industry, goes even further with the claim to validity of its standards. In its self-image, the observance of SIA standards guarantees Baukultur (building culture) itself.

Considering the broad consensus with which the respectively valid SIA standards are recognised, it may be surprising at what rate the set of rules is changed. Standards are incessantly revised to adapt them to changed framework conditions. These revisions, as well as the numerous newly added regulations, reflect the constantly rising safety, health, and comfort demands of an increasingly wealthy society. It would now actually be assumed that with ever tighter regulation, the achievement of climate goals would become more probable. However, that is not the case: revisions of SIA standards are not coordinated to achieve sustainability goals. Contradictions arise from this.

These conflicting goals become obvious when building further within the existing fabric. To reduce CO2 consumption in the building sector, the preservation of existing buildings with the embodied energy built into them long ago could actually contribute a great deal. But existing buildings do not only stand in the way of achieving economical use of land for the purpose of internal densification. Historical buildings are based, if at all, on long outdated and mostly laxer standards. If the current SIA standards designed for new buildings are applied to the existing stock, conflicts therefore arise. For many building parts and components, preservation is more complex than replacement. The effort and benefit of individual construction measures, for instance in energy retrofits, must therefore be carefully analysed and weighed up in every case – in ecological, economic, and design terms. If compliance with current standards is declared the supreme goal, things usually look bad for the existing stock.

One of the biggest drivers for replacement buildings is the impossibility of meeting currently valid building acoustics standards by means of renovation. The problem exists primarily with floor structures in older apartment buildings. It is considered unreasonable to hear noises from neighbours a floor below or above, and if the deficiency cannot be renovated away, the house must go, according to current practice. However, the same standards have also led to questionable practices in the floor structures of new buildings. In terms of building components, floors account for the largest share of the CO2 balance, which should actually create incentives for material savings. Instead, concrete flat slabs have established themselves as the standard, becoming thicker and heavier over the last decades to meet continuously increased building acoustics requirements with additional mass. The problem is exacerbated by poor, but common system separation: building service pipes such as ventilation ducts are often laid into the slabs, which significantly reduces sound insulation values and must be compensated for with additional concrete thickness. These strange habits result in the fact that often not the structural engineer, but the building acoustician determines the slab thickness.

What the SIA can always point to when its standards and their effects come under criticism: standards reflect a social consensus. They show a mirror of social demands – of a society with contradictions, which sets itself climate goals and yet lives beyond its means. Thus the circle closes. We live in a society where climate goals are gladly repressed; where in 2021 a stricter CO2 law was rejected at the ballot box; where the year-round guarantee of an indoor climate between 21 and 26 degrees is taken for granted; where it is considered normal to fly on holiday twice a year; where the petrol or electricity consumption of private vehicles is considered a private matter, etc. The construction industry is embedded in the context of this society. Is it therefore surprising with what persistence the construction industry cultivates and defends its practices?

The great transformation in the construction industry can only succeed if the idea of sufficiency gains a different status within society. This fact should not discourage us, but spur us on to work for improvements. As architects, we can achieve more in the construction industry than we think. Resource-optimised design takes place in the everyday life of architectural offices. System separation in construction should become as natural as separating household waste. And SIA standards are made by experts, including committed architects. It is therefore also up to us and our engagement to establish new, resource-saving standards through association work.

Concrete

Although the Roman opus caementicium was already widely used, it was not until the béton armé introduced by François Hennebique in 1892 or the "mushroom slab" patented by Robert Maillard in 1908 that building with concrete was significantly further developed and versatilely applied. However, the interim intensive engagement with rod-shaped construction methods such as the filigree cross-ribs of the Gothic period or the wide-spanning roof trusses and wooden bridges by Hans Ulrich Grubenmann (1709–1783) were groundbreaking for a successful structural engineering development of the "new" material concrete.

Concrete can be load-bearing and also space-enclosing. Hardly any other building material has such a wide field of application as reinforced concrete: walls, flat slabs, columns, frames, beams, barrel vaults, shells, etc. Therefore, it is suitable for bridges and tunnels, foundations and retaining walls, for massive and skeleton construction methods as well as for rod-shaped prefabricated building elements and high-quality spatial enclosures. Its widespread application is also due to the fact that reinforced concrete is extremely high-performance, cost-effective, and structurally simple to implement.

Tectonic potential is achieved in particular by the joining of prefabricated concrete elements. Groundbreaking in this regard were Angelo Mangiarotti's (1921–2012) industrial buildings masterfully implemented in Northern Italy, where in addition to high structural performance and efficient assembly processes, the tectonic joining and the specific shaping of the individual elements were thematised.

The application of concrete is increasingly being questioned due to its poor CO2 and energy balance. Due to a lack of alternatives, however, it is inevitable that reinforced concrete will continue to find wide use. For this, cement production must be optimised, new recipes applied, and material consumption significantly reduced in its overall balance through additional effort in formwork and reinforcement technology. Paired with the great potential to use reinforced concrete specifically only where it is high-performing and can be synergetically combined through suitable fasteners and in composite with other materials.

Character (Expression)

Based on the finding that "a general loss of quality of the built environment" is emerging, the social importance of a high-quality Baukultur was officially established by European Ministers of Culture in 2018 in the run-up to the World Economic Forum. For political and strategic anchoring, the so-called "Davos Quality System for Baukultur" with "Eight criteria for a high Baukultur" was adopted. Interesting here is the eighth assessment criterion to be fulfilled: the aspect of BEAUTY. With a view to future-proof and sustainable architecture, this often marginalised aspect was thus officially defined as a social necessity. It is now up to us architects to fundamentally include the search for an architectural expression with a positive appeal to emotion in the design.

The charisma and character of a building are based on its spatial and material presence. Thus, the material conditions of building are a direct and decisive parameter for an immediate and sensuous expression – and fundamental importance is attached to the constructive design. It not only regulates technical and building physics requirements, but always also defines an order in the interplay of components, as symbolised for instance by the term tectonics. In every constructive structure, relationships are formulated: relationships of the components to one another, but also scale relationships from the small to the large, from the building to the observer, etc. According to studies in happiness research, humans are strongly oriented towards relationships – and in Hartmut Rosa's "Sociology of the Good Life", for instance, "resonant" relationships are a yardstick and fundamental prerequisite for a fulfilled life. In this sense, it is not absurd to see constructive design, with the potential for orchestrating relationships that resonate with us, as a fundamental instrument for a fruitful search for the aspect of beauty – and ultimately for happiness.

Design for Disassembly (DfD)

Design for Disassembly pursues the goal of designing buildings in such a way that they can be dismantled into reusable individual parts at the end of their service life. This relies on reversible connection techniques such as screw or plug connections to separate components from one another without damage, instead of permanent methods like gluing or welding. True DfD is only achieved when all components of a building can be dismantled individually and exactly in the reverse order of the assembly process. In the context of circular construction, DfD is a central approach, as buildings are no longer viewed as a final product, but as temporary material depots. DfD is particularly effective for above-ground components, while foundations or underground infrastructure, due to their construction method, can only be constructed reversibly with difficulty. Prefabricated, modular systems reinforce the advantages of DfD: standardised modules and connections allow complete building parts to be dismantled and reused elsewhere. This reduces the consumption of new raw materials and extends the lifespan of materials.

However, the practical implementation of DfD entails some challenges. Currently, legal standards and targeted incentives to promote the reuse of used building elements are lacking. The reuse of structural components also requires complex certifications, and dismantling a building often takes more time and incurs higher costs than traditional demolition. In addition, reversible constructions often require additional material usage and increased constructive complexity. For example, prefabricated concrete elements often require supplementary in-situ concrete for final stiffening, which makes the system irreversible. A completely dry connection system, on the other hand, demands more connecting elements made of steel and possibly additional concrete or steel. Likewise, reversible timber connections often require more complex joints with metal plates and screws, while permanent solutions like welding are simpler, yet not dismantlable.

Historically, there are significant projects that have successfully implemented DfD principles. As early as 1851, the Crystal Palace in London was erected as a modular pavilion made of glass and steel, dismantled after the exhibition, and rebuilt elsewhere – an early example of reversible building. Jean Prouvé developed modular steel houses in the mid-20th century, the components of which could be assembled and dismantled as often as desired. Renzo Piano conceived a mobile IBM exhibition pavilion in the 1980s that was relocated and rebuilt multiple times. Contemporary projects like Werner Sobek's residence R128 in Stuttgart, which consists entirely of dry-assembled steel and glass elements, also show the high potential of DfD. In Zurich, Bauart Architects created schools in timber module construction with the Züri-Modular programme, which are flexible and reversibly usable. Pool Architekten also realised modular sports halls with reversible constructions here.

Windows (Reuse)

Windows are essential building elements that not only let daylight into interiors but also contribute significantly to energy efficiency and living comfort. In recent decades, window technologies have developed considerably, especially with regard to thermal insulation and soundproofing.

A significant advance was the development of insulating glass. While older windows consisted only of a single pane of glass, modern windows rely on multi-pane insulating glazing with gas fillings such as argon or krypton. These gases as well as optimised spacers minimise heat losses and improve energy efficiency. In addition, today's windows have Low-E coatings that reflect thermal radiation and thus prevent both heat losses in winter and overheating in summer.

Thermal insulation is evaluated by the so-called U-value – the lower this value, the better the window insulates. Modern triple glazing achieves values below 0.6 W/m²K. The g-value, which indicates how much solar energy passes through the window, also plays a role in the passive use of heat.

The reuse of windows is a major challenge because their technical properties are difficult to assess. Factors such as manufacturer, type of glazing, and frame material significantly influence a window's performance. Important parameters for reuse are the U-value, the g-value, and light transmission. Sound insulation, air tightness, and safety aspects must also be considered.

Some manufacturers mark windows with technical specifications in the spacer, but in Switzerland there is no uniform standard for this. This makes the classification and further use of windows considerably more difficult.

The dismantling of windows can be demanding, as today's installation methods (according to current standards) use adhesives, sealants, and spray foam to guarantee air tightness, sound insulation, and fire protection. These materials make removal complicated, as windows are firmly bonded to the wall.

Embodied Energy

Embodied energy (often referred to as Graue Energie in German contexts) is frequently used in architectural discussion as a synonym for a building's ecological footprint, as the term played a central role at the beginning of the ecological discussion. In the leaflet SIA 2032, embodied energy is defined as follows: "Total amount of non-renewable primary energy in the construction area" (Merkblatt SIA 2032, Graue Energie – Ökobilanzierung für die Erstellung von Gebäuden, Zurich 2020). This means that the sum of fossil energy carriers expended for the extraction, production, and disposal of a building material is taken into account. The result is given in the unit "kWh oil-eq.", whereby all fossil energy carriers used are converted into oil equivalents. For this reason, it does not matter which non-renewable energy carrier was ultimately used in the life cycle of a building material.

With progressing climate change and the goal of reaching Net Zero in greenhouse gas emissions by 2050, the focus is shifting from embodied energy to greenhouse gas emissions. As with embodied energy, greenhouse gas emissions are a value used to quantify the Life Cycle Assessment. Greenhouse gases are expressed in the unit kg CO2-eq., with CO2 serving as the reference quantity, even if, for example, methane (CH4) has a 28 times greater global warming potential, or nitrous oxide (N2O) a 273 times greater potential.

A further indicator is Environmental Impact Points, or UBP (Umweltbelastungspunkte). These have been calculated since 1990 according to the method of ecological scarcity. The FOEN (Federal Office for the Environment) defines the method as follows: "Here, the tolerated target quantities are based on the legally anchored Swiss ... goals" (Ökofaktoren Schweiz 2021 gemäss der Methode der ökologischen Knappheit, BAFU, Bern 2021), i.e., a value linked to the goals of Swiss environmental policy and taking into account factors that show how far we are currently removed from the target values. UBP take into account the ecological footprint of a building material by including, for example, resource consumption, biodiversity, toxicity, and ten other categories.

In every object to be examined, the different characteristic values can be used for calculations to make a specific statement about sustainability. The leaflet SIA 2032 reports construction assemblies in "kWh oil-eq./m2", while the standard SIA 390/1 calculates with "kg CO2-eq./m2". The reference per "m2" usually refers to the energy reference area (definition see SIA 380/1) and enables a comparison of different building projects or constructions. However, this reference quantity is not sensible for every building task. Therefore, the Life Cycle Assessment can also be reported per gross floor area (see SIA 416) or per person.

Hempcrete

Hempcrete (also known as hemp lime) is a composite building material made from one of the oldest cultivated plants and the proven building material lime. The mineral-biogenic mixture consists of four parts hemp shives – a waste product from the industrial fibre production of industrial hemp – and one part each of aerial lime and water. As a natural thermal insulation material, the building material offers excellent moisture and temperature regulation. It also scores with positive properties in fire protection as well as in sound insulation. Hempcrete binds 150 per cent of the emitted CO₂ emissions over its entire service life and can be reused and recycled. A monolithic wall of about 40 cm thickness is sufficient to meet current thermal insulation standards.

The mixture is used in various ways: tamped on site, pressed into bricks and air-dried, or by means of spraying methods. When setting in the air, quicklime first reacts with water and subsequently carbonises with the carbon dioxide of the ambient air. The result is a solid, but not load-bearing building material that can be worked with simple tools and is suitable for self-building. Due to the low load-bearing capacity, hempcrete requires a skeleton construction of timber, steel, or concrete. At the end of its life, hempcrete can be crushed and fully reused by adding a small amount of lime. Current Swiss legislation prohibits reuse as compost for soil improvement; this would be technically feasible, but releases the bound greenhouse gases again.

Despite the widespread basic materials, hempcrete remains a niche product in current architecture. Only in France does the building material find wider distribution, as the use of industrial hemp was never banned there. In the course of the transformation to a climate-responsive construction industry, hempcrete offers great potential, which is currently being researched at several universities.

Timber

Timber as a building material lies in the area of tension between tradition and innovation. As a material with deeply rooted traditions, timber has experienced a veritable boom in recent times, driven by the climate crisis and digitalisation. As a renewable raw material, it combines high load-bearing capacity with low dead weight. In Central Europe, timber is regionally available, easy to process, and binds CO₂ during growth via photosynthesis. As a durable component, it stores carbon, and both in processing and at the end of life, timber allows for cascade use right up to the biochemical utilisation of cellulose, lignin, or tannin. One cubic metre of utility timber grows in Switzerland within four seconds; according to the FOEN, only slightly more than half of the potential was harvested in 2023.

Timber is not a homogeneous material. Its properties vary depending on growth, location, and species. The choice and use of the timber ideally takes place in direct relationship to the natural form of the raw material. In addition to solid timber, engineered wood products such as glulam or particle boards are used today, which enable high dimensional stability or large spans through industrial production and also make inferior raw material usable.

Constructive challenges exist in fire, sound, and weather protection. The hygroscopic properties of timber, i.e., its ability to absorb and release moisture, influence the construction and the design formulation. Durability depends essentially on constructive measures: protection of the end grain, ventilation, covering, and avoidance of direct ground contact.

The tendency to view timber as the exclusive option for climate-responsive building should be critically questioned. The non-optimised use of engineered wood products also raises questions about material justice, the use of fossil adhesives, and the constructive logic of the starting material.

Its simple workability and the tradition of prefabrication favour the digital production of precise elements, from compact systems to five-axis milled free-form beams. Joining decisively shapes timber construction. Historically, timber was often joined by pure wood connections without glue or metal, an expression of a material-appropriate and craft-based understanding of building. Today, glued or metallic connections dominate, enabling rational prefabrication. In combination with other materials, hybrid constructions arise that combine the advantages of timber with the properties of other materials and at the same time open up as yet unexhausted room for innovation.

Hybrid Floor Systems

Floor systems usually consist of a load-bearing structure, floor buildup, and ceiling cladding. The term hybrid describes the use of different materials in the load-bearing structure. In many cases, this enables a material-efficient construction method, as the respective materials are used according to their strengths and complement each other. In multi-storey construction, floors serve for load transfer and space enclosure. This essential task is performed by the load-bearing structure; it often also serves to stiffen the building. In combination with floor buildup and ceiling cladding, existing requirements for fire and sound protection are achieved. Through a multi-layered construction setup of different material layers, heat can be stored where necessary, the transmission of structure-borne and impact sound reduced, and fire flashover from one storey to another prevented. Building service pipes are also often routed within the floor assembly. Due to the diverse requirements, different floor systems have developed. Depending on the type of construction and materials used, they differ in their weight, the height of the assembly, and their Life Cycle Assessment, in addition to their performance.

Construction

Following the etymological meaning of the Latin construere (con = together; struere = to layer on top of or next to each other), constructing describes the geometric ordering and assembling of parts. Construction in architecture can be defined as the ordering and layered joining of materials and components, which determines their interaction in a building. What appears in the building in physical form is based on the designed disposition of architects, which is first established in precise construction drawings and later transferred into built reality by various trades. Thus, building construction assumes a bearing significance in architecture in the sense that it makes the material implementation of a design idea possible in the first place and thus represents an indispensable component of architectural design.

Structures are divided into load-bearing structure, building envelope, and interior envelope, or simplified: into load-bearing framework and enveloping cladding. Both are characterised by the properties and conditions of material and connection and determined in their essence by physical and constructional laws. Building construction in turn receives its specific, formal appearance via materiality. Architectural expression and construction correspondingly always stand in immediate reciprocal action. Constructive solutions must correspond to the currently valid rules of the building art, are thus anchored in their time, and are based on substantial, available, building-cultural knowledge. Moreover, building construction is always committed to practical suitability in order to guarantee the long-term preservation of structures. Construction does not follow the formal, architectural intentions of the designers alone and supremely – constructing rather represents a multi-layered, multi-faceted process that seeks to bring design, functionality, and building technology into harmony.

Earth

Earth (or loam) is regionally available, requires little energy for processing, and is fully reusable. In contrast to concrete or bricks, it causes hardly any CO₂ emissions.

Earth is formed by the weathering of rock and consists of gravel, sand, silt, and clay. The clay content determines the binding power, while the other components contribute to stability. Earth has a high thermal storage capacity and can thus balance out temperature fluctuations and thereby increase the energy efficiency of buildings. In addition, thanks to its moisture-regulating properties, it contributes to a pleasant indoor climate.

However, there are challenges: earth is sensitive to water and has a low load-bearing capacity. Nevertheless, modern research and new production techniques open up promising possibilities. Hybrid construction methods combine earth with timber or concrete to expand its application. Prefabricated earthen building elements enable faster construction methods and increase efficiency.

Earth is usually extracted on site, which avoids long transport routes and energy-intensive manufacturing processes. Moreover, it is completely reusable – a building made of earth can become soil again at the end of its life.

Earthen building techniques are versatile: rammed earth is compacted in layers and forms stable walls. Adobe bricks, formed from moist earth and air-dried, offer simple processing. Light earth, enriched with straw or wood shavings, improves thermal insulation and allows lighter constructions.

Although earth has proven itself over many centuries, it was hardly developed further as a building material in recent decades. Now numerous research projects are underway to optimise industrial production processes and construction site workflows. Thus, earth could play an important role in climate-responsive building in the future.

Life Cycle Assessment (LCA)

A meaningful indicator for the assessment of sustainability is the Life Cycle Assessment (LCA). Through the LCA of building materials, constructions, buildings, and even settlements, statements can be made about their environmental impacts. Ultimately, all everyday processes can be described with an LCA, which is also known as "Life Cycle Analysis". The chosen object of observation is divided into 16 process phases (A–C) along its life cycle using standardised methods. This overall view takes place in the classical sense from cradle to grave, beginning with raw material supply (A1) and ending with disposal (C4). This linear phase view can also be adapted for circular use.

In the construction industry in Switzerland, the leaflet SIA 2032 "Embodied Energy – Life Cycle Assessment for the Construction of Buildings" defines the procedure for calculating an LCA. The leaflet in turn serves as the basis for the standard SIA 390/1 "Climate Path" as well as for various building labels. For the basic data, all calculation models rely on the values of the "LCA Data in the Construction Sector" of the KBOB (https://www.kbob.admin.ch/de/oekobilanzdaten-im-baubereich). In a comprehensive Excel table, interested persons get access to material characteristic values such as embodied energy (kWh oil-eq.), greenhouse gas emissions (kg CO2-eq.), environmental impact points (UBP), and the biogenic carbon stored in the material (kg C).

The calculation of an LCA requires a quantity survey of all construction assemblies, the entire building envelope including underground components and interior walls.

Pedagogy of Construction

In the perception of architecture, the constructive detail appears as a material counterpart thanks to the concrete material level of expression, radiating an immediate effect. Thus, the constructive formulation of a structure is of fundamental importance and must be developed precisely with the architectural design. Just as the meaning of a word in spoken language depends on the context and changes depending on the context, in architecture too, the structural, constructive detail gains its meaning only from the overall urban and cultural context. The construction never stands alone, but requires urban interpretation and cultural perception, which act as catalysts to lend meaning to the design process. One's own design stance plays a decisive role here.

Here, putting individual constructive elements into relationship – both with one another and in the larger context – can only be learned and practised if a multitude of viewing levels are taken into view simultaneously and different scale levels are worked on in parallel. Conveying this is the focus of architectural construction theory.

Our word construction (from Lat. con-struere = to construct) is based on the Latin root struere, which in its original meaning means to layer, to pile up. The same root also underlies instruction, i.e., teaching, guiding. While one is about joining components, the other is joining know-how. Building is therefore related to teaching insofar as both are about meaningful layering. Both are edifying activities.

Render

Render (or plaster) is a material of the surface, for together with paint it forms the outermost protective layer of a facade construction, the so-called "sacrificial layer". Like human skin, this protective layer requires constant care and repair or renewal within the life cycle. Render is probably one of the most underestimated building materials; render is the material of everyday life. The impression is deceptive: as simple as render is in its appearance, its composition and its dependence on the construction beneath it can be complex. Especially with the disappearance of monolithic external wall construction and the associated dissolution of the wall into individual layers, combined with the emergence of External Thermal Insulation Composite Systems (ETICS), the formerly simple rendered facade became a complex component.

Render is not a material that can be extracted from nature like timber or natural stone. It is a building material composed of several materials. Renders are composed of binders such as lime or cement, aggregates such as gravel and sand, and water. Additives such as pigments may be added. Until industrialisation, render was a regional building material – lime came from the local lime pit, sand from the sand pit, and gravel from the river. Put simply: there are as many renders as there are sands. The world of render surfaces is infinitely diverse. There are the most varied surface finishes such as scratched, thrown, smoothed, combed, or stencilled. There is a close connection between tool, grain size of the render, and application technique: the type of surface treatment is already inscribed in the render mixture; smooth renders, for example, can only be processed with small grain and high sand content. If the render is not applied by machine but by a craftsman, it bears their individual handwriting. Thus, every hand-applied render is unique and a one-off.

Steel

Steel is a collective term for materials consisting mostly of iron. Compared to traditional building materials like timber, natural stone, and brick, steel was not accepted as an independent material in the construction industry for a long time; iron served as a highly loadable fastener, but not as a building material with architectural expressive potential. Thus, in the Greek temple, metal bolts connect columns and architrave, or in Notre Dame de Paris, thousands of steel cramps connect the natural stone walls. It was not until the second half of the 19th century, with the triumph of the railway in infrastructure buildings like stations and bridges, public buildings like the dome of the Federal Palace (Bundeshaus), or exhibition architecture like the Eiffel Tower, that steel gained broader acceptance as an independent building material.

Structural steel has an unrivalled modulus of elasticity of 210,000 N/mm², whereas spruce, also a high-performance building material, reaches just 6,000 N/mm² in the fibre direction. Disadvantages are corrosion upon contact with oxygen (not toxic to humans) and poor fire resistance.

Our view of steel today is shaped by the industrialisation of the 19th century. Starting from England, there was strong growth in heavy industry for coal and iron ore throughout Europe. Blast furnaces fired with coke (degassed coal) allowed for the first time the large-scale and cheap production of pig iron. While at the beginning of the 19th century about 0.02 million tonnes of steel were produced per year in Europe, this amount increased a hundredfold at the end of the 19th century to 2 million tonnes; a sheet metal and steel industry emerged. Metal entered everyday life, from the automobile to mechanical engineering to seating furniture. Global steel production now amounts to 2,000 million tonnes. It is the only material that can be recycled without loss of quality; worldwide, about a quarter of the tonnage today comes from reuse.

The numbers speak for themselves; the application of steel in industry is undisputed. The Institute of Constructive Design at the ZHAW has shown and explored the spatial and constructive potential of steel in residential construction as well, based on three historical and six contemporary examples in the widely noticed research work Zuhause im Steel (At Home in Steel).

Sufficiency

The term "sufficiency" stands for the right measure in the sense of "sufficing" (from Lat. sufficere = to be enough, to suffice). In the sustainability debate, it stands for the lowest possible energy and resource consumption. In a broader sense, it stands for appropriateness, reduction to the essential, and self-limitation right up to renunciation of consumption. The term was first used in the German-speaking world in 1993 by Wolfgang Sachs. According to Sachs, the terms "efficiency" ("dematerialisation", saving of energy and resources) and "consistency" ("nature compatibility", use of regenerative resources) must be supplemented by "sufficiency" ("self-limitation", restriction and renunciation). Only in the interplay of all three terms can the gap between growing demand and shrinking resources be closed and truly sustainable, future-proof models be developed.

While efficiency and consistency are generally accepted and recognised, as they are measurable as quantitative categories and can be supported by data, sufficiency is difficult to describe and convey. It is a qualitative category that is perceived individually and is not measurable. In general, it is associated with a restriction of freedom, comfort, and prosperity. A "less is more" is difficult to convey convincingly, especially since the "less is more" of Modernism has fallen into disrepute through abstracting solutions as too ascetic and hostile to life. Yet renunciation was already seen as a gain in monastic societies. However, in a society based on individual freedom, "sufficiency" cannot be decreed. It is therefore the most difficult sustainability strategy to convey and naturally comes up short in discussion and application compared to the technically shaped solution approaches of efficiency and consistency.

At best, "sufficiency" is associated with cost-effective building. But it points beyond that, for example, to the lowest possible use of building technology in "Low-Tech" solutions or with regard to the newly discussed "Building Standard E". An important step is the reduction of individual living space from 40 m² to 26 m² in the city of Zurich, which leads to a gain for society by enabling more flats (Housing and Commercial Settlement Guggach III, Foundation Einfach Wohnen Stadt Zürich).

Tectonics

The term "tectonics" is derived from the Greek word tekton, which means "carpenter" or "builder". In the work of the Greek poet Sappho (6th century BC), the carpenter significantly also assumes the role of the poet. In the 19th century, Gottfried Semper defined the term as "the art of joining rigid, rod-shaped parts into an inherently immovable system". The two practical aestheticians Gottfried Semper in the German-speaking and Eugène Viollet-le-Duc in the French-speaking cultural sphere dealt with the question of style that arose in the age of advancing industrialisation. Both sought the answer to this question in the logic and correctness of the constructive joining of building components and devised two different, indeed opposing models of thought. While Semper ascribes the protagonist role for the spatial definition of a building to the constructive cladding elements – Tectonics of Cladding – for Viollet-le-Duc it is primarily the elements of the building structure – Tectonics of Bearing – that should determine the formation of space and the architectural expression of a building.

The present digital construction theory attempts to trace the "logic and correctness" of tectonic joining in the age of digitalisation. The representation of assembly sequences as well as the possibility of viewing 3D models from different angles use the advantages of the digital medium over the traditional print medium. Thus, the animations also draw attention to the increasingly procedural aspect of tectonic joining in connection with the omnipresent topics of emissions and resource conservation, as well as to the future perspective in which the process of building will be increasingly connected with that of deconstruction. In the context of our school of architecture, the digital design theory is intended to give our students a tool with which they can work on their own stance as responsible professionals beyond the development of their projects.

Typology of Construction

The complexity of self-imposed and external requirements in design, planning, and building is high. Originally conditioned by local, cultural construction methods, but having become virulent through industrialisation and the associated standardisation, typologies are always defined for the demarcation and ordering of "systems". The term "typology" is etymologically composed of "model" and "science" or "doctrine".

Typology can therefore not only be understood as the science of ordering and classifying, but much more also as a "process of type formation". The collection and application of typologies must therefore be open and dynamic. Crosses and hybrids of existing types favour the development of new construction solutions, provided they spring from an internal logic. Decisive here are considerations of "joining", which come about due to (perhaps new) material properties and construction principles.

Prefabrication

Prefabrication as a concept in architecture and the construction industry describes the industrial production of building elements or entire building parts with the aim of optimising construction processes, reducing costs, and increasing quality. The term refers to the process of systematic, often modular production of building elements, which are prefabricated in a factory and then assembled on the construction site.

The idea of prefabrication has a long tradition reaching back to antiquity. However, particularly since industrialisation, it has become a central topic in architecture and construction.

With industrialisation in the 19th century, prefabrication was used on a large scale for the first time. In England, Joseph Paxton introduced one of the first examples of industrial prefabrication in construction with his Crystal Palace. The entire structure of the building consisted of prefabricated glass and cast iron elements, which were assembled in a modular construction method.

In the 20th century, prefabrication increasingly moved into focus, especially after the Second World War, when the demand for quickly available and affordable housing was enormous. In numerous European countries, standardised panel systems were developed and used between the 1950s and 1980s to create living space on a large scale.

Although industrial prefabrication was considered a promising solution for mass housing in the 1950s to 1980s, it failed in many places due to social, urban planning, and technical challenges. The low adaptability of these systems and the lack of identification of residents with their homes increasingly led to the rejection of this typology among the population.

While prefabrication in concrete lost importance, it established itself in modular timber construction as a central construction method of the present.

Reuse of Components

In our built environment, the existing stock is usually demolished for new buildings. The materials are cleanly separated and if possible sent for recycling, but the large amount of energy required to produce form-fitting components is destroyed. Building with reused components is therefore an effective option today for reducing the CO2 emissions of new buildings.

If reuse remains a rare exception in today's construction industry, which is characterised by time and cost pressure, the repeated use of valuable parts was historically the rule rather than the exception. Not for ecological, but much more for economic considerations, worked building components were considered valuable already in prehistoric times, in the high cultures of antiquity, or in the vernacular buildings of our mountain cantons, and were reused in new buildings wherever possible.

Beyond economic pressure, the reuse of building materials was also an expression of respect for the craftsmanship of the past. Relicts of historical structures were formed into something new with painstaking devotion and visibly incorporated into new buildings. Today, too, reuse opens up the transfer of the history inherent in the components into new buildings. Surprising new allocations can prove to be a chance to establish a new architectural expression.

Building with reused components is a further question for our generation of architects in our generalist job profile, for which we must acquire the corresponding constructive and architectural competencies. The ability to assess the economic, social, energetic, and building-cultural value of building substance is a further field whose laws we must understand and weigh up naturally and responsibly in every building task.