By 2050, the Dutch construction sector is required to be fully circular, where bio-based materials can play a promising role in this transition. However, the implementation of bio-based materials is currently limited due to a lack of technical design knowledge within the sector. Additionally, the hygroscopic properties are insufficiently understood, which further hinders the integration of bio-based materials into building designs. The main objective of this thesis is therefore to develop validated 1:5 scale bio-based façade wall reference details for residential top-up buildings that perform well in reducing thermal bridges and ensuring effective moisture transport. The research combines a literature review with research-by-design and digital simulations. Initially, the advantages and disadvantages of bio-based construction materials over conventional ones are examined. Following this, five bio-based materials (cork, flax, hemp, straw, and wood) are selected and incorporated into the developed bio-based reference details. Design principles were first established to ensure the correct implementation of these materials. In total, this thesis presents 11 detail configurations, consisting of 33 validated bio-based reference details. These details were evaluated using the simulation software WUFI for moisture transport, mould growth, surface condensation, and thermal bridges. The thesis outlines both the methodology and the results. The first configuration is discussed in detail in the main report, while the remaining ten validated configurations are included in the appendix. In addition, this thesis presents 33 additional reference details which were not validated but are expected to show similar performance to the validated ones. Based on the simulation results, most of the detail configurations meet the requirements for moisture regulation and thermal performance. The isopleth analyses indicate that mould growth does not occur within the tested material layers in most configurations. Furthermore, no surface condensation was observed at the most critical points within the details. The results also comply with Dutch regulations regarding limited thermal bridging, with the measured values comparable to those of the ‘ISSO reference details’. These simulation results hereby demonstrate that the developed bio-based reference details can be effectively used in residential top-up buildings. However, the established design principles and vapour permeability must be maintained. When applied correctly, the selected bio-based materials can prevent mould growth and surface condensation, while keeping thermal bridging to a minimum. Although the simulations provide valuable insights, the validation is limited by the exclusive use of WUFI. Next, only a medium moisture load for indoor climates and the NEN 5060 for outdoor climates are used making the assessments only representative for the Netherlands. Future research could validate the results using alternative simulation software and by considering various climatic and moisture conditions. Before the developed details can be applied in the Dutch market, additional research must explore the remaining building physics aspects and structural requirements. Nevertheless, the developed design principles and validated reference details provide a solid foundation for the further implementation of bio-based construction in Dutch residential buildings.