Wood-based hygromorphic materials for sustainable responsive architecture

PhD ThesisAdaptive building systems that are able to adjust their properties depending on ambient conditions in order to regulate and employ the effects of natural light, heat and ventilation on the interior building environment can help address the challenges of continuously maintaining occupant comfort whilst reducing the energy use of buildings. The climate-sensitive behaviour of contemporary adaptive systems is usually achieved by means of technologically-imposed intelligence. The detection and interpretation of the external stimuli and control and actuation of the response in these systems are performed by separate mechanical and electrical components. This results in their dependency on energy supply, high complexity and cost and potential reliability and maintenance issues which hinders wider diffusion of smart technologies in mass housing market. This points to the need for alternative design approaches that could combine the simplicity of zero-energy bioclimatic design and the dynamic adaptive capacities of high-tech smart architecture. The inspiration for such an approach can be drawn from nature where elegance and functionality often coexist and the robustness and efficiency of responsive systems, such as conifer cones, is enabled by the employment of inherent properties of their constituent materials. The structure of the responsive scales of conifer cones can be artificially replicated to produce low-tech low-cost smart materials with passive mechanical response to variable levels of atmospheric moisture that is driven by shrinkage and swelling of wood (hygromorphic materials). Previous work on wood-based hygromorphs has provided a proof of concept of this technology and has demonstrated that it can potentially be applied in large-scale adaptive building systems. Yet, the key properties of the materials that determine their applicability in architecture have not been studied sufficiently. This project expands the existing knowledge about wood-based hygromorphs by establishing the principles for selection and fabrication of their material configurations, describing methods for pre-programming and numerical modelling of their cyclic response and exploring the long-term durability of the materials. The opportunities and challenges for deployment of wood-based hygromorphs in architecture are discussed in the context of a wide range of sustainability considerations