Practical Use of Materials of Natural Origin as Loose-Fill Insulations in Open-Diffusion Constructions—Observation and Numerical Simulation

The increasing requirements concerning the consideration of the environmental impact of building materials, along with the simultaneous preservation and enhancement of building thermal parameters, have led to a surge in interest in insulations based on organic or recycled materials. Despite the growing interest in these materials, there remains a scarcity of scientific studies regarding their hygrothermal properties. Within the scope of the research described in the text, the insulation properties of loose-fill materials (hemp shives, cellulose fibers, loose wood wool, and mineral wool as a reference) in wooden frame walls were analyzed. The authors simulated walls with the same U value filled with these materials using Delphin 6.1 software. The simulation time was 3 years, considering the appropriate climatic conditions of Olsztyn and different microclimatic conditions inside the rooms. Insulations made of natural organic can absorb and reveal moisture to the internal environment, while mineral wool transports the moisture to the outside, which may cause condensation problems. Insulations made of hemp shives or wood wool do not increase the level of accumulated moisture over time, which results in thermal stability. In contrast, cellulose and mineral wool store more moisture, which in wet conditions increases the heat flux by 6.9% and 5.2%, respectively.