InterTwig—Willow and Earth Composites for Digital Circular Construction

The construction sector has high resource demands and generates a significant amount of waste, a consequence of its linear approach. A shift towards renewable and local material sources and the implementation of closed material cycles represent a significant opportunity for the construction industry to curtail the depletion of raw materials. To address these challenges, this paper presents a strategy for a novel circular construction method that combines willow, a rapidly renewable material, with earth and is enabled by digital fabrication, which can sustain their industrialisation through tailored processes. Emerging from a materiality perspective, the research revisited vernacular building techniques that used plant- and earth-based composites, exemplified by the vernacular wattle and daub, to understand how these can be enhanced through digital design and digital fabrication. Willow (Salix) is a woody 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. To use willow for construction, geometry and textile techniques were implemented to create stable structures. In combination with earth, a finite but abundant and infinitely recyclable material, it creates a sustainable and circular composite that exploits the structural characteristics of each constituent material. Digital design methods enabled the exploration of different geometrical variations and ensured an increased degree of control over their complexity at different scales. The research results were tested in a full-scale prototype, demonstrating the principles of the envisioned construction systems.