ReGrow Willow is an innovative hybrid material system that combines the tensile strength of willow and the compressive strength of earth for architectural applications. The Karlsruhe Institute of Technology also uses digital fabrication processes and computational tools to create lightweight, mobile, and adaptable fabrication equipment.
The project further seeks to present a potential remedy for resource depletion and waste generation. Willow is a rapidly renewable material that grows up to two meters annually and replenishes yearly after harvesting.
The digitally prefabricated components are designed to be reusable thanks to simple, reversible screw connections. Once they have reached the end of their life cycle, the earth can simply be washed out and repurposed. The willow stems and other natural fiber reinforcement can be composted.
A comprehensive fabrication system was developed, starting with a two-axis machine capable of extruding and depositing continuous macro-fibres made from spliced willow stems.
The earth is shot into selected cells within the willow formwork using a plastering machine that employs high-pressure pneumatic extrusion.
The geometry of the willow formwork allows for seamless integration with the earth, eliminating the necessity for any additives or adhesives.
The ReGrow Willow research demonstrator in Mannheim, Germany, demonstrates the possibilities of digitally fabricated willow-earth components. To illustrate a holistic transition to creating a sustainable built environment, it also incorporates concepts of microclimatic adaptation and local energy harvesting.
The installation comprises 63 prefabricated components that incorporate a joinery system for assembly connections, enabling a fast assembly process completed in three stages, each taking two days.
Earth is primarily used at the foundations and willow predominating at the top. Two finishing treatments are used to assess weathering impact, an important challenge for earthen construction.
The willow-earth building system is also being developed as horizontally spanning reinforced earth floor slab.
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