This diploma thesis is dealing with sheep wool and its thermo-insulating features. In the first part of this work we will clarify what are the basic thermophysical properties. Then we will look to composition of sheep wool and its physical and mechanical properties, which will lead us exactly to values needed when designing thermal protection for buildings according to Slovak Technical Standard STN 73 540-2. Equally important part of this work is dedicated to degradability and ecology of thermo-insulating materials including sheep wool. Next section is about types of sheep wool insulation and its application in wooden houses. Design of thermo-insulating building envelope with use of sheep wool as insulation is also included in this section. In the last theoretical part we will look to preparation and processing of sheep wool into various semi-products, which can be used in engineering. Then we will make samples from these semi-products and use them in experiment in the practical part of this thesis. The experiment will help us to identify thermophysical properties of various sheep wool semi-products. The aim is to specify the relationship between thermal conductivity and change of density. To collect these data we used extended dynamic plane source method EPDS. This method is nonstationary. I will be working mostly with books about thermal protection of buildings, with the latest researches in sheeep wool properties and with the results of the experiment.