The main goal of this master thesis is experimental research of change in thermal conductivity depending on the depth of the char layer and weight loss of wood fiber matherials in the process of thermal degradation. The thesis consists of two main sections. The theoretical section is devided into four chapters. The first chapter descibes the fundamentel structure of wood, its composition, and burning technological properties. The second chapter focuses on large-scale wood based materials, different wood types and specific characteristics, especially wood fiberboards of which samples are used for this experiment. The third chapter describes used raw materials, production process and use of glues in fiberboard production. The fourth chapter analyses the termophysical properties which are tested in this thesis. The practical section focuses on the way of conduct the experiment which is the main goal of this thesis. It describes used raw materials, measuring devices and calculations of termophysical properties. Finally, it graphically represents and evaluates measured and calculated values.