The main objective of this study is to examine the heat insulation potentialities of the incorporation of wood wool in a sand mortar, in order to value the use of this type of lightened materials as lightweight insulating concrete. The wood wool has been incorporated, without any preliminary treatment, into a sand mortar. Four mortars containing different ratios of wool have been prepared and have been examined herein. It was shown that the incorporation of wood wool in the mortar decreases considerably its thermal conductivity and diffusivity. Thus, the thermal insulation capacity has been improved. Also, the influence of the water content on the thermo physical properties of the studied samples has been examined. Thus, the thermal conductivity increases rapidly with water content and the thermal diffusivity presents a maximum corresponding to a water content value $W_m$. However, the materials used for building constructions must present sufficient mechanical strength. According to the experimental results, the compressive strength values are compatible with the use of these materials as lightweight concrete. The examination of the water absorption of the studied samples shows the high hygroscopic nature of the elaborated composite.