The interest in low-energy, sustainable architecture and consequently, in buildings with minimized environmental impact has been growing over the years. As a result, the use of bio-based insulation, as well as constructionmaterials, has become more and more prevalent in many countries around the world. Today the market share of bio-based insulation materials is well below 10% worldwide. In Germany, where the market share has increased by 2% points in the past 10 years, the share of bio-based building insulation reached 9% in 2020 which is among the highest in the EU. Almost 60% of these are wood fiber materials another 30% are based on cellulose fibers and the last 10% include all other bio-based insulation products. The hygrothermal performance of bio-based materials, especially theirmoisture buffering capacity and their high vapor permeability represent real benefits, while themoisture susceptibility is the most important downside.