A key feature of architecture is the constant adaptation of external influences such as culture, climate, and ideologies. Architects have always been eager to develop new concepts, analyze existing problems, and transform them into preferred situations. Architecture is influenced by the changing needs of society. In order to adapt to these demands, there is a constant process of rethinking and improving established typologies. Through innovative new developments, the present spirit of the time (Zeitgeist) is used and formed to find sustainable solutions for the architectural and structural problems of our time.
However, the constant further development of architecture’s form and function is still continuously achieved by the guidance of a rigid linear design thinking process. This classical design tool is based on a fundamental idea, whose emphasis follows the order: defining the problem, brainstorming, problem solving, and finally, testing [1
]. It was this specific design tool structure that made it possible to develop most of the current adapted architectural solutions.
Although many ecological problems could largely be improved by architecture, the approach of applying specific ecologically friendly materials as a first phase in the design approach is still not largely applied. Due to the need for rapid reconstruction and the high housing shortage, the post-war architecture missed a sufficient discussion with important factors such as the ecological influence and the re-usability after the building elements’ relatively short life cycle, such as for instance building skins that have an approximate lifespan of around 20 years [2
]. The still current guiding principle of the construction industry is anchored in the ‘take, make, waste’ principle [3
]. In Europe, this leads to up to 50% non-recyclable construction waste [4
The construction sector account for more than 35% of global final energy use, nearly 40% of energy-related CO2
], and almost 45% of global resources consumption. As the global population will grow from seven billion to almost nine billion by 2040, the demand for resources will rise exponentially so that by 2030, the world will need at least 50% more food, 45% more energy, and 30% more water at the same time when environmental boundaries will have new limits to supply, especially with climate change [6
]. Aggregate materials and concrete are currently the predominant building materials by weight used in Europe, which together with high-emission materials such as steel and aluminum are responsible for the largest share of greenhouse gas (GHG) emissions stemming from the building sector [7
]. This paradigm from cradle to grave is no longer feasible, which is why the search for sustainable alternatives is of great importance.
The multidisciplinary cooperation among experts from different scientific worlds, including specifically material engineering, architecture, and structural engineering, as well as possibly biologists, physicists, and others, facilitates huge benefits in setting new circular architectural design philosophies, in which each scientific branch creates an input in the design process. Through this collaboration, another strategy to start the architectural design process may totally differ. In this case, the whole design can start by selecting a specific alternative material, which can be for instance biomass-based, to have the ecologic feedback that is needed, and can be further combined with smart design methods that enable combining the building elements in a way that allows dismantling options for re-use in a later stage.
In previous research work by Lepelaar et al. [8
], the usage of green building materials, especially biocomposites, was considered in the design phase of a pedestrian bridge that was built in the campus area of Eindhoven University of Technology (TU/e)in Netherlands. The researchers here worked in a multidisciplinary manner to meet the mechanical requirements as well as the aesthetic ones.
In this paper, the freedom of design was offered when specified green building materials were set as a start input in the design process. Here, linear design thinking was not applied, and a new circular design thinking, which started with ‘Materials as a Design Tool’, took place. In this case, the choice of materials—especially bio-based materials—were the starting point, followed by defining and customizing the material properties, applying diverse form-finding strategies using parametric design methods, conducting structural analysis and applying digital fabrication technologies to finally prefabricate the building elements.
In this case, defining building materials became no longer a subsequent step that follows the linear design phase; rather it became the circular design’s strong foundation. Accordingly, a new design philosophy was established and practiced. The usage of materials’ capabilities as a main input in the design process opened the door to the opportunity to develop more sophisticated solutions to address diverse architectural challenges.
This design philosophy ‘Materials as a Design Tool’ was combined with concepts that could enable dismantling options, which is referred to as ‘Design for Deconstruction’ (DfD) [2
], to be applied in the form of small and large-scale mock-up structures. The guiding principles were the applied modular structure systems. In this case, the focus was on the simple and logic design of the individual components. In order to reach a proper economic impact, the individual building elements should be always prefabricated in a suitable handy size to ensure quick assembly and disassembly [9
] that do not require special training. Computational form-finding and different fabrication methods can with help achieving structural and material-saving efficiency, which can ensure a positive building balance, hence helping in the reduction of the total CO2
footprint. Therefore, materials cannot simply be regarded as constants. Depending on the desired usage, the selected material should be further developed, customized, and adapted. From the beginning of the design phase, prototyping, mechanical tests, and numerical simulation methods are capable of showing the materials’ capacities and structural performances. Material fabrication is also an important factor, because the manufacturing processes, such as for example extrusion, drilling, or casting also have an influence on both the material behavior and the geometrical variations.
The author here strives to find effective ecologic solutions in the building industry through starting with materials as a design tool, where the research and development of sustainable biomaterials is set as a starting point in the architectural design process. The intention is to produce building elements and systems that are CO2-neutral, recyclable, and/or compostable, and could be partially if not completely produced from biomass resources. This could be only achievable through close cooperation between architects, engineers, material experts, and others. One of the applied materials in the case studies was biocomposite fiberboards manufactured from agricultural by-products such as straw, which is the annual rest-over released after harvesting cereal crops, bound by thermoplastic and thermoset organic binders. The fiberboard structure was dependent on the different binders and applied fabrication techniques, which together settled the main architectural design drivers.
In the following part, three case studies are analyzed, which highlight the philosophy of ‘Materials as a Design Tool’ combined by the ‘Design for Deconstruction’ concept through individual applications. Each of the three pavilions illustrates the benefits of modular construction with green building materials, which were used as architectural and structural elements. The research pavilions were materialized by different green building materials, whether purely structural or not.
Flexible biocomposite fiberboards, [11
], elastic wood-based middle-density fiberboard (MDF) boards, and recycled ‘cartoon’ tubes were chosen as the main materials by the author/architect to be applied as a start driver in the design process. In each case, the selected materials were customized to the needed structural capacities. In the design process, the focus was on not only the usage of bio-based materials, but also above all an in-depth examination of possible end-of-life scenarios, including re-using the building elements that would increase the validation of the circular bioeconomy, which is another scope that is needed regionally, especially at the European level [12
Biocomposites can act as partial replacement to wood, as well as a partial replacement to the classic fiber-reinforced polymer composites (FRP), as this group of materials lie basically between those mentioned materials (wood and FRP). Accordingly, in order to be able to apply these new alternative sustainable materials, it is always needed to mechanically test them after testing the codes of the relevant materials, such as FRP and wood/polymer composites (WPC), so as to apply standardization and verification to settle how reliable the alternative materials are, according to the frame of Eurocodes, to suit the needed applications in reality. This was especially considered in the first case study, which is the largest prototype shown in this paper. In previous work by the author, the improvement of the fire behavior of other developed biocomposites to suit wider applications in architecture was reached [13
The three analyzed case studies were realized by the Department of Bio-based Materials and Material Cycles in Architecture (BioMat) at the Institute of Building Structures and Structural Design (ITKE) at the Faculty of Architecture and Urban Planning of the University of Stuttgart under the author’s supervision.
In all three case studies carried out between 2011–2018, the philosophy of ‘Materials as a Design Tool’ was applied, where green building materials were given a priority to be set as the main driver behind the whole design process until the construction phase. The basic idea, which characterized the three pavilions, was to design modular, reusable closed material systems, based on a strong examination of the building material as an initial stage in the design process. The designs of the research pavilions always focused in detail on their own specific architectural challenges and illustrated their implementation through the use and purposeful modification of different green building materials, such as wooden-based fiberboards, recycled cartoon pipes, or biocomposites.
The most recently constructed BioMat Research Pavilion 2018, which was exhibited on the campus of the University of Stuttgart, focused on finding innovative solutions for modifying a flexible, elastic biocomposite material in a way that allowed it to perform structural functions, as well as create a unique aesthetic configuration. The selection and analysis of the materials in the design process determined not only the global geometry of the pavilion, but also the order, size, and shape of the individual elements of the modular building systems.
The Biomimetic Research Pavilion 2018 depended on the analysis of an interesting stacking/interlocking feature of a biological role model. With the help of the abstracted designs, it was possible to develop an assembly/dismantling method to allow full control over the end-of-life scenarios. The elastic yet self-supporting material properties were also settled in the initial design phase, and for this, wood-based MDF panels were the settled applied materials for this project. Through in-depth analysis, the biological-inspired structures were actively bent and locked in the desired positions to transform the settled integrated concepts into an architectural realm. By this bio-inspired interlocking tooth-like design of individual building elements, a quick dismantling and reassembling was guaranteed. Accordingly, the shell-shaped structure offered the possibility of performing a wide variety of tasks, and could be mounted in different locations.
The third research pavilion, the Eco-Pavilion 2011, was primarily an illustration of the DfD approach combining different green building materials and establishing sustainable building systems. Unlike the other two pavilions, the fundamental idea of the structural framework and the material composition was not re-developed. Here, recycled cartoon pipes were modified by carving slots for the wooden joints, which acted as ‘dry’ structural connections. This recycled and recyclable structure was applied as a background to other biocomposite products, recycled cladding products, and flooring products.
The three research pavilions represent not only the use of green building materials in architectural applications, but also the results of multidisciplinary work. In these projects, architects were not only pure designers, since the close cooperation with external experts naturally expanded the field of the architects’ work. The knowledge gained from material researchers led to functional adaptations of the building materials. The circular design exchange with civil engineers, fabrication technicians, and other external specialists regularly showed the capabilities of introducing the material in the design process, allowing an expression of a new philosophy in design-thinking, based on setting ‘Materials as a Design Tool’. This led to a high level of design creativity and solutions in modular building systems. By constantly adapting to functional demands, the individual components developed their own aesthetics.
In the following, Table 1
, an analytical comparison of the three case studies is illustrated.
The innovative application of newly developed green building materials and their digital fabrication possibilities were the main drivers in the design thinking process, introducing new perspectives of design and establishing new design philosophies. The strong involvement of the choice and characteristics of the materials from the beginning of the design process establishes new ways to develop ideas, which helps solve architectural problems in a much more sustainable way.
Through in-depth knowledge of the properties of these building materials and the ability of further customizing them to reach up to advanced properties and controllable end-of-life scenarios, more sustainable building concepts were developed. The possibility of the individual composition of these green building materials ensured a controlled and directed closed life cycle, which was defined by recyclability, compostability, re-usability, and a holistic improvement of the ecological footprint.
Since the newly developed biocomposite fiberboards were, unlike wood, not bound to a predefined fiber configuration, the same base material enjoyed the ability to function as an insulating, structural, or purely aesthetic building component, according to changes in its internal recipe and by combining it externally with reinforcing elements. That happened especially in the first case study.
In order to ensure further future sustainable solutions within architectural designs and guarantee their implementations, it is important to develop and apply modular building systems that can be assembled and dismantled to allow proper material savings. This will allow the possibility of applying the same building system in different applications. The use of biocomposites and biomaterials with their ability to be adapted and customized to various structural capabilities is a suitable solution for a wide range of new developed architectural applications, which is hereby in many ways proved.
The limitations of this suggested design philosophy’s usage of setting ‘Materials as a Design Tool’ depend on the depth of the architects’ interdisciplinary work and the level of their interest in technicalities and other related disciplines to architecture, such as material developments and fabrication techniques. That is why the development of an architectural design process that manifests itself through the choice of materials, structure, aesthetics, and above all, sustainability, was only made possible by a stronger linking of different fields of studies, such as the areas of natural sciences, construction, material scientists, and fabrication experts, and their exchange of experiences. The multidisciplinary exchange allowed the development of more sustainable and intelligent solutions for architectural challenges, since not only a linear exchange of knowledge took place through materials research, but communication between the architects and experts of diverse disciplines was also established.
Adopting ‘Materials as a Design Tool’ as a design philosophy is hereby initiated from the author, and highlighted through different developments in the form of pavilions and prototypes to spread the word in the architecture community, so as to help initiate this field of design-thinking and philosophy toward more sustainability in the near future of architecture.