ReGrow Willow
Basic information
Project Title
ReGrow Willow
Full project title
Natural Composites for Digital Circular Construction
Category
Shaping a circular industrial ecosystem and supporting life-cycle thinking
Project Description
ReGrow Willow is an earth-willow hybrid structure for architectural and construction applications, promoting low emissions construction technologies and circular material cycles enabled by cutting-edge bespoke digital fabrication and computational tools. As a digital reinterpretation of vernacular construction methods, it showcases a novel construction system based on rapidly renewable bio-based material and earth, which can be composted or recycled at the end of the life cycle.
Geographical Scope
Regional
Project Region
Baden Württemberg, Germany
Urban or rural issues
It addresses urban-rural linkages
Physical or other transformations
It refers to a physical transformation of the built environment (hard investment)
EU Programme or fund
No
Description of the project
Summary
The project ReGrow Willow presents an earth-willow hybrid structure for architectural and construction applications that enables circular material cycles through bespoke digital fabrication systems and computational tools. Reinterpreting the European vernacular wattle and daub material system, this project introduces an alternative resource stream in which willow, a rapidly renewable bio-based material, can be composted at the end of its life cycle, while earth remains infinitely recyclable without loss of value. ReGrow Willow aims to reintroduce irregular locally grown low embodied energy materials into scalable contemporary construction practice through digital technologies and diversify the repertoire of grown building materials by complementing classical forestry products. The synergistic combination of willow serving as tension reinforcement for the earth, is advanced through tailored computational workflows while the development of customised fabrication processes hints at the scalability potential of the prefabricated building elements. Additionally, integrative digital design tools manage the interdependencies between architectural design, material systems, structural performance, and fabrication processes.
The implementation in a full scale construction demonstrator addresses multiple target groups such as decision makers and political representatives, the general public, stakeholders of the construction sector such as architects, civil engineers and the building industry as well as researchers and innovators.
The underlying research of the project delves into the complete value chain, examining local sourcing and into which steps to take in order to create a sustainable, circular product for market applications that are both affordable and replicable.The project aims towards a short term reduction of emissions in construction and a long term perspective for circularity in sustainable architecture though fully recyclable and waste free construction.
The implementation in a full scale construction demonstrator addresses multiple target groups such as decision makers and political representatives, the general public, stakeholders of the construction sector such as architects, civil engineers and the building industry as well as researchers and innovators.
The underlying research of the project delves into the complete value chain, examining local sourcing and into which steps to take in order to create a sustainable, circular product for market applications that are both affordable and replicable.The project aims towards a short term reduction of emissions in construction and a long term perspective for circularity in sustainable architecture though fully recyclable and waste free construction.
Key objectives for sustainability
This project aims to introduce an innovative circular construction method that integrates willow, a renewable bio-based material, with earth and is enabled by digital fabrication, which can sustain their industrialisation through tailored processes. Willow is a fast-regrowing plant native to Europe whose stems can be harvested yearly, thanks to specific forestry practices, namely short rotation coppice, that allow the plant to regenerate in rapid cycles. This is an advantage compared to timber and can diversify the renewable materials used in construction. When combined with earth, an abundant yet finite resource, it forms a natural composite where willow serves as tension reinforcement for the earth, enabling a scalable application of local natural building materials as alternative to established steel reinforced concrete building elements.
The construction system is designed to work with reversible, easily accessible joinery systems. This means that the structure can be easily taken apart using reversible connections, facilitating partial or whole repurposing. Eventually, the materials can be separated into earth-based and plant-based components. The earth can be recycled for new construction, while plant-based materials can return to the biosphere, contributing to the regeneration of renewable resources.
Additionally, the project incorporates microclimatic adaptation and local energy harvesting concepts. The integration of plants and water evaporation is employed to locally reduce temperatures, exemplifying a comprehensive transition towards sustainable future construction and climate adapted built environment. This approach not only addresses the construction materials' life cycle but also embraces environmentally conscious strategies for enhancing local climates and harvesting energy sustainably.
The construction system is designed to work with reversible, easily accessible joinery systems. This means that the structure can be easily taken apart using reversible connections, facilitating partial or whole repurposing. Eventually, the materials can be separated into earth-based and plant-based components. The earth can be recycled for new construction, while plant-based materials can return to the biosphere, contributing to the regeneration of renewable resources.
Additionally, the project incorporates microclimatic adaptation and local energy harvesting concepts. The integration of plants and water evaporation is employed to locally reduce temperatures, exemplifying a comprehensive transition towards sustainable future construction and climate adapted built environment. This approach not only addresses the construction materials' life cycle but also embraces environmentally conscious strategies for enhancing local climates and harvesting energy sustainably.
Key objectives for aesthetics and quality
The design methodology prioritises the creation of a construction system through the development of its constituent parts, adopting a bottom-up approach. It explores an architectural language rooted in materiality and fabrication systems, leveraging the functional and intricate complexity achievable through digital design and fabrication. These digital workflows empower architects, engineers and users to experiment with diverse designs, adjusting them to meet specific goals while navigating the complexities of implementing an innovative construction method.
To enable a seamless integration of this construction method into architecture and construction, ReGrow Willow is a research demonstrator whose design intent is to test the research but also to make the research accessible to everyone and serving as a focal point for discussion with the general public. The project is presented as a series of walls forming semi-enclosed spaces with diverse themes, ranging from energy harvesting integration on buildings to the microclimate aspect, which enhances the onsite visitors' experience.
Structure, form, design, fabrication, circularity and function each become expressive elements coexisting and participating together, while maintaining their unique characteristics. The design language is conveyed through the interplay of open and filled meshes, which highlights the combination of the delicate and intricate filigree of willow with the robustness embodied by the earth and willow components.
The digital reinterpretation of historic local and natural building materials, willow and earth, presents an immediately appealing and widely accepted design language. This is achieved through straightforward, low-tech building elements that emerge as not only relevant and scalable but also economically, ecologically feasible, and poised for future-proof construction practices, leveraging the intricate complexities of high-tech digital design and fabrication processes.
To enable a seamless integration of this construction method into architecture and construction, ReGrow Willow is a research demonstrator whose design intent is to test the research but also to make the research accessible to everyone and serving as a focal point for discussion with the general public. The project is presented as a series of walls forming semi-enclosed spaces with diverse themes, ranging from energy harvesting integration on buildings to the microclimate aspect, which enhances the onsite visitors' experience.
Structure, form, design, fabrication, circularity and function each become expressive elements coexisting and participating together, while maintaining their unique characteristics. The design language is conveyed through the interplay of open and filled meshes, which highlights the combination of the delicate and intricate filigree of willow with the robustness embodied by the earth and willow components.
The digital reinterpretation of historic local and natural building materials, willow and earth, presents an immediately appealing and widely accepted design language. This is achieved through straightforward, low-tech building elements that emerge as not only relevant and scalable but also economically, ecologically feasible, and poised for future-proof construction practices, leveraging the intricate complexities of high-tech digital design and fabrication processes.
Key objectives for inclusion
The project aims to create accessible and affordable system, starting from relatively inexpensive materials to custom but open-source and low-cost technology for the fabrication process. This approach ensures widespread adoption of the sustainable building system. The fabrication process, rooted in low-complexity, cost-effectiveness, and versatility, involves custom-made machines built from mostly readily available and inexpensive hardware store components. By applying these principles to the development of fabrication processes for bio-based materials, the emerging technologies can enable the reduction of the dependence on specialised craft while allowing production scalability and automation feasibly. This adaptable approach holds the potential for transferring the building system to diverse regions, accommodating different materials and contexts. Ultimately, it promotes accessible, tailor-made fabrication solutions for communities typically excluded by cost, availability, or specialized knowledge barriers.
Results in relation to category
The project ReGrow Willow serves as a tangible design and technology demonstrator for waste free circular and digitally enabled construction methods. During its research development fundamental aspects of fabrication automation for inhomogeneous natural materials have been addressed and documented in scientific publications and conference presentations. The exhibition at the Buga 23 in Mannheim opened the scientific expert discourse towards a wider public including decision makers and political leadership.
A central investigation of the project was dedicated to the wider context of a local bioeconomy and sustainable circular material streams in construction. Willow can be cultivated in flood prone areas thus circumventing a land use competition with classical forestry or agriculture zones. In cooperation with the Ministry for Rural Areas in Baden-Württemberg, former wetlands which are currently emitting substantial amounts of greenhouse gases were identified for renaturation as wetlands in combination with willow cultivation. While the emissions from former wetlands can be stopped the rapidly growing willow plantations can simultaneously sequester substantial amounts of CO2 during their rapid growth. The potentially available willow cultivation wetlands in Baden-Würrtemberg have been identified and quantified as a substantial source of fast regrowing construction material, substantiating the concept of a scaled application of willow/earth construction elements.
ReGrow Willow provides the knowledge base for currently ongoing applied research and development of a certified ceiling construction component, covering structural, fire, and sound certifications in preparation for the architectural application of fully certified willow/earth/wood hybrid ceiling components. We anticipate exploring its market potential in 2025. Given the urgency of climate concerns, the speed of innovation and its practical scalability is crucial for a societally relevant impact.
A central investigation of the project was dedicated to the wider context of a local bioeconomy and sustainable circular material streams in construction. Willow can be cultivated in flood prone areas thus circumventing a land use competition with classical forestry or agriculture zones. In cooperation with the Ministry for Rural Areas in Baden-Württemberg, former wetlands which are currently emitting substantial amounts of greenhouse gases were identified for renaturation as wetlands in combination with willow cultivation. While the emissions from former wetlands can be stopped the rapidly growing willow plantations can simultaneously sequester substantial amounts of CO2 during their rapid growth. The potentially available willow cultivation wetlands in Baden-Würrtemberg have been identified and quantified as a substantial source of fast regrowing construction material, substantiating the concept of a scaled application of willow/earth construction elements.
ReGrow Willow provides the knowledge base for currently ongoing applied research and development of a certified ceiling construction component, covering structural, fire, and sound certifications in preparation for the architectural application of fully certified willow/earth/wood hybrid ceiling components. We anticipate exploring its market potential in 2025. Given the urgency of climate concerns, the speed of innovation and its practical scalability is crucial for a societally relevant impact.
How Citizens benefit
The project, a spatial structure featuring interconnected arched walls to create semi-enclosed spaces, serves as a tangible representation of the research and the design possibilities. The research demonstrator was constructed at the c in Mannheim, Germany. This event format has historically provided a platform for architectural innovations, particularly in the local context of Mannheim, where Frei Otto realized the "Multihalle" for the BUGA exhibition in 1975. On one hand, this choice aimed to raise awareness about potential solutions for a more environmentally conscious future. On the other hand, the choice of such a prominent event, with a diverse audience, was deliberate, allowing for engagement with a broad cross-section of the public and fostering open discussions. This was further highlighted by the choice of building the demonstrator in three phases so it would be possible for people to observe, interact and discuss with the researchers on site.
On-site research included gathering public feedback through questionnaires. These surveys inquired about the visitors' overall experience and thoughts and, more specifically, their perceptions of microclimatic aspects and comfort levels.
To bolster this outreach, a symposium on "Natural Resources in Digital Circular Construction" was conducted on-site, facilitating dialogue between the public and leading European researchers in the field of sustainable construction. In this way, the project served as a bridge between research and society, making research findings accessible to a broader audience.
On-site research included gathering public feedback through questionnaires. These surveys inquired about the visitors' overall experience and thoughts and, more specifically, their perceptions of microclimatic aspects and comfort levels.
To bolster this outreach, a symposium on "Natural Resources in Digital Circular Construction" was conducted on-site, facilitating dialogue between the public and leading European researchers in the field of sustainable construction. In this way, the project served as a bridge between research and society, making research findings accessible to a broader audience.
Physical or other transformations
It refers to a physical transformation of the built environment (hard investment)
Innovative character
ReGrow Willow has the potential to expand the possibilities and architectural language of earth construction and holds significance for the broader adoption and diversification of renewable materials in architectural applications.
In comparison to contemporary attempts to reintroduce earth structures into construction, that are constrained by either limited craftsmanship or a repertoire of robotically extruded elements based on compression, ReGrow Willow broadens the structural possibilities of earth structures. The repertoire of feasible components could then be extended to elements that are affected by tensile forces, such as beams. This is achieved through biogenic tension reinforcement and enhanced scalability via digital prefabrication processes. It lays the groundwork for a significant transformative potential with societal relevance, currently being further explored in subsequent research projects. Recent research stemming from ReGrow Willow has produced a horizontally spanning, universally applicable slab component, structurally certified to withstand 3.5 times the loading capacity of the steel-reinforced concrete benchmark. Developments like these underscore the significance of demonstrator projects, such as ReGrow Willow, as catalysts for a digital and sustainable transformation in the built environment.
In comparison to contemporary attempts to reintroduce earth structures into construction, that are constrained by either limited craftsmanship or a repertoire of robotically extruded elements based on compression, ReGrow Willow broadens the structural possibilities of earth structures. The repertoire of feasible components could then be extended to elements that are affected by tensile forces, such as beams. This is achieved through biogenic tension reinforcement and enhanced scalability via digital prefabrication processes. It lays the groundwork for a significant transformative potential with societal relevance, currently being further explored in subsequent research projects. Recent research stemming from ReGrow Willow has produced a horizontally spanning, universally applicable slab component, structurally certified to withstand 3.5 times the loading capacity of the steel-reinforced concrete benchmark. Developments like these underscore the significance of demonstrator projects, such as ReGrow Willow, as catalysts for a digital and sustainable transformation in the built environment.
Disciplines/knowledge reflected
The objective of the research was to devise an integrated digital process that could include all aspects of architectural design, component production, assembly and construction in a holistic approach. Simultaneously, it sought to incorporate pioneering concepts capable of influencing local urban microclimates and propose strategies for local and sustainable energy cycles. It also aimed to establish tools for assessing and guiding such innovations, particularly through lifecycle assessments.
To achieve this, a collaborative and interdisciplinary team was essential, comprised of researchers and students specializing in architecture, structural design, mechanical and automation engineering, building physics, technical building services, photovoltaics, and lifecycle assessment. On one front, the research focused on creating digital algorithmic models that could visualize the various scales and implications for design and construction right from the initial design phases. This also involved conducting physical prototypes and tests to generate valuable feedback loops. The research methodology therefore intertwined design, performance, and fabrication processes, supporting the digital redevelopment of traditional material systems, their processing, and digital manufacturing.
On another front, it involved the concurrent development of architectural design and research themes centered around microclimatic conditions, local energy harvesting, and feedback loops with the life cycle assessment of this innovative material system in order to inform the development of the overall construction system.
Finally, by involving students at every step, at the interface of research and teaching, the project aspires to continue shaping the future of construction. It emphasizes, from the early stages of education, that construction can and should serve as a domain for experimentation.
To achieve this, a collaborative and interdisciplinary team was essential, comprised of researchers and students specializing in architecture, structural design, mechanical and automation engineering, building physics, technical building services, photovoltaics, and lifecycle assessment. On one front, the research focused on creating digital algorithmic models that could visualize the various scales and implications for design and construction right from the initial design phases. This also involved conducting physical prototypes and tests to generate valuable feedback loops. The research methodology therefore intertwined design, performance, and fabrication processes, supporting the digital redevelopment of traditional material systems, their processing, and digital manufacturing.
On another front, it involved the concurrent development of architectural design and research themes centered around microclimatic conditions, local energy harvesting, and feedback loops with the life cycle assessment of this innovative material system in order to inform the development of the overall construction system.
Finally, by involving students at every step, at the interface of research and teaching, the project aspires to continue shaping the future of construction. It emphasizes, from the early stages of education, that construction can and should serve as a domain for experimentation.
Methodology used
The ReGrow Willow project is evolving through an innovative research and education strategy, situated at the crossroads of interdisciplinary exploration. This approach swiftly translates speculative and forward-looking investigations into tangible, application-focused prototypes. The innovation pipeline operates at the intersection of research and teaching, where it expeditiously evaluates cutting-edge digital circular construction concepts via exploratory prototyping within research-oriented teaching formats. Subsequently, it transitions these concepts into interdisciplinary research grants.
After an extensive exploration of speculative concepts in teaching formats, the most promising ideas undergo testing in 1:1 prototypes to generate pertinent research questions for interdisciplinary research grants. The construction, technological, and architectural potential of the research outcomes is subsequently assessed through full-scale demonstrator projects like ReGrow Willow. These projects serve as comprehensive proof of concept implementations, offering visibility and forming the basis for evaluating economic and ecological application potential under market conditions in architectural building projects. This process serves as preparation for technology transfer to industry partners or university spin-offs.
In just two years, our research on willow-earth composite structures achieved rapid success. We explored digitally enabled design and fabrication concepts for willow structures, integrating them with earth as a hybrid material system in 1:1 demonstrators within teaching formats. This provided future architects with crucial insights for sustainable construction. Subsequent in-depth research on digital design and fabrication methods for willow/earth hybrid construction received funding through projects like "ReGrow" and "WillowWeave." These methods were successfully tested at the Bundesgartenschau Mannheim 2023 in the "ReGrow Willow" demonstrator project.
After an extensive exploration of speculative concepts in teaching formats, the most promising ideas undergo testing in 1:1 prototypes to generate pertinent research questions for interdisciplinary research grants. The construction, technological, and architectural potential of the research outcomes is subsequently assessed through full-scale demonstrator projects like ReGrow Willow. These projects serve as comprehensive proof of concept implementations, offering visibility and forming the basis for evaluating economic and ecological application potential under market conditions in architectural building projects. This process serves as preparation for technology transfer to industry partners or university spin-offs.
In just two years, our research on willow-earth composite structures achieved rapid success. We explored digitally enabled design and fabrication concepts for willow structures, integrating them with earth as a hybrid material system in 1:1 demonstrators within teaching formats. This provided future architects with crucial insights for sustainable construction. Subsequent in-depth research on digital design and fabrication methods for willow/earth hybrid construction received funding through projects like "ReGrow" and "WillowWeave." These methods were successfully tested at the Bundesgartenschau Mannheim 2023 in the "ReGrow Willow" demonstrator project.
How stakeholders are engaged
This research underscores the significance of conducting a multidisciplinary investigation that involves collaboration with farmers, industry, governmental organizations and policymakers.
From a feasibility standpoint, it engaged closely with local willow growers within a 20-kilometer radius of the research location to assess factors such as availability, various willow species, forestry practices and the future potential for large-scale production and application.
Likewise, the research reached out to various participants in the earth construction value chain, encompassing companies specializing in earth mixtures and local machinery manufacturers relevant to the implemented processes. This aimed to support the development of the fabrication process.
The research received funding from the Baden-Württemberg Ministry of Food, Rural Areas and Consumer Protection (MLR) as part of the Bioeconomy Innovation Programme for Rural Areas. This funding was crucial in aligning the research with the needs and potential of the local region, while also fostering a relationship with policymakers. The project, its underlying research results, its implications and requirements for future societal, economic and ecologic frameworks that enable a circular bioeconomy in construction were presented and discussed with political representatives such as German federal and Baden-Würrtemberg state ministers as well as members of the parliament and the Minister-President of Baden-Württemberg. The project's outreach also benefitted from the involvement of BioPro, a state agency dedicated to catalysing the transition of the economy and society towards bioeconomy, enhancing the connectivity between society, industry, and research.
Finally, the project's association with the Federal Horticultural Show served as a platform to showcase microclimatic conditions for urban interventions and present the entire project, from the forestry of bio-based materials to application, to the general public.
From a feasibility standpoint, it engaged closely with local willow growers within a 20-kilometer radius of the research location to assess factors such as availability, various willow species, forestry practices and the future potential for large-scale production and application.
Likewise, the research reached out to various participants in the earth construction value chain, encompassing companies specializing in earth mixtures and local machinery manufacturers relevant to the implemented processes. This aimed to support the development of the fabrication process.
The research received funding from the Baden-Württemberg Ministry of Food, Rural Areas and Consumer Protection (MLR) as part of the Bioeconomy Innovation Programme for Rural Areas. This funding was crucial in aligning the research with the needs and potential of the local region, while also fostering a relationship with policymakers. The project, its underlying research results, its implications and requirements for future societal, economic and ecologic frameworks that enable a circular bioeconomy in construction were presented and discussed with political representatives such as German federal and Baden-Würrtemberg state ministers as well as members of the parliament and the Minister-President of Baden-Württemberg. The project's outreach also benefitted from the involvement of BioPro, a state agency dedicated to catalysing the transition of the economy and society towards bioeconomy, enhancing the connectivity between society, industry, and research.
Finally, the project's association with the Federal Horticultural Show served as a platform to showcase microclimatic conditions for urban interventions and present the entire project, from the forestry of bio-based materials to application, to the general public.
Global challenges
The construction industry, with its high resource demands and substantial waste generation, operates on a linear model where resources are extracted, utilized, and ultimately discarded as waste. This project showcases a shift towards alternative, local sourcing and material usage, presenting an opportunity for the global construction sector to minimize raw material depletion and embrace circular material cycles.
Examining vernacular architecture, particularly the European wattle and daub method, reveals a sustainable construction approach. This traditional method incorporates bio-based, renewable, and locally-sourced materials like willow or poplar, combined with earth-based materials, forming an environmentally friendly composite. While such vernacular techniques have been overshadowed by the industrial revolution, this research proposes a localized approach that harnesses the customisation potential of digital design and fabrication towards the development of a digital circular construction. The underlying methods can serve as a model for revitalizing architecture closely tied to its environment. This approach can lead to a construction and architectural practice where development strategies, workflows, and open-source technologies become shared foundations for a novel global approach, rather than a standardised global style.
Furthermore, the project addresses challenges in the built environment by integrating innovative concepts. It proposes solutions that can locally impact microclimates within cities, such as incorporating plants and water mists. Additionally, these are supported by strategies for local and sustainable energy cycles are advocated, with the integration of solar panels as a tangible example. By actively engaging with these challenges, the project promotes a holistic and sustainable approach to construction and architecture, contributing to a more environmentally conscious and locally responsive built environment.
Examining vernacular architecture, particularly the European wattle and daub method, reveals a sustainable construction approach. This traditional method incorporates bio-based, renewable, and locally-sourced materials like willow or poplar, combined with earth-based materials, forming an environmentally friendly composite. While such vernacular techniques have been overshadowed by the industrial revolution, this research proposes a localized approach that harnesses the customisation potential of digital design and fabrication towards the development of a digital circular construction. The underlying methods can serve as a model for revitalizing architecture closely tied to its environment. This approach can lead to a construction and architectural practice where development strategies, workflows, and open-source technologies become shared foundations for a novel global approach, rather than a standardised global style.
Furthermore, the project addresses challenges in the built environment by integrating innovative concepts. It proposes solutions that can locally impact microclimates within cities, such as incorporating plants and water mists. Additionally, these are supported by strategies for local and sustainable energy cycles are advocated, with the integration of solar panels as a tangible example. By actively engaging with these challenges, the project promotes a holistic and sustainable approach to construction and architecture, contributing to a more environmentally conscious and locally responsive built environment.
Learning transferred to other parties
To replicate and transfer elements of the project, the portable and cost-effective machine, easily deployable for prefabrication from local sources, presents a scalable model adaptable to diverse regions.
In a wider perspective, the custom digital design workflows and fabrication technologies offer a model for revitalising an architecture that is deeply tied to its environment, addressing local climate, resources, and culture. This fosters a construction practice where shared foundations, inclusive of development strategies and open-source technologies can encourage the emergence of sustainable vernacular architecture. The methodology also serves as a model for developing novel construction systems through interdisciplinary exploration.
Advancing to the next stage, the willow-earth hybrid component logic is applied to create floor slab components, adding relevance to the building industry and paving the way for mass market applications. Certification in fireproofing and sound insulation is targeted for 2024.
Finally, highlighting the cross-pollination potential of the project, the bio-degradable willow components are currently being investigated as a way to help restore coastal ecosystems.
In a wider perspective, the custom digital design workflows and fabrication technologies offer a model for revitalising an architecture that is deeply tied to its environment, addressing local climate, resources, and culture. This fosters a construction practice where shared foundations, inclusive of development strategies and open-source technologies can encourage the emergence of sustainable vernacular architecture. The methodology also serves as a model for developing novel construction systems through interdisciplinary exploration.
Advancing to the next stage, the willow-earth hybrid component logic is applied to create floor slab components, adding relevance to the building industry and paving the way for mass market applications. Certification in fireproofing and sound insulation is targeted for 2024.
Finally, highlighting the cross-pollination potential of the project, the bio-degradable willow components are currently being investigated as a way to help restore coastal ecosystems.
Keywords
Natural materials
Digital circular design
Novel construction systems
Local and vernacular materials
Bespoke digital fabrication
