Seven new different thermo-insulating materials based on wool and /or skin wastes were obtained. To emphasize this capability, the effective thermal diffusivities were determined at a material moisture content of 10%, in a temperature range of 10 to 40oC. Depending on the material composition, the results showed that the effective thermal diffusivity varies between the limits of 6E-8 and 8.5E-8 m2/s. The smallest values were obtained for the untreated wool and for the material obtained from both untreated wool and finished leather powder. The obtained values underline the fact that the investigated materials can be used to obtain composites with good thermo-insulating properties.