Current policies addressing the energy efficiency of buildings aimed at the control of their overall primary energy demand, require not only that the edifice envelope has to be properly designed to optimize its thermal performances, but also that the eco-friendly properties of the involved building materials have to be properly taken into account, in order of assessing all the associated environmental costs. In fact, the design of envelope structures that are able to realize proper levels of thermal insulation and, in the same time, to employ materials characterized by low environmental impacts, are believed as the most effective strategies to be adopted in the aim of addressing the above-mentioned issues. In this regard natural materials, such as vegetal fibres or materials derived from the recycling of industrial/ agricultural waste, reveal very attractive characteristics. Indeed, recent studies on the use of natural materials in buildings concentrate on raw materials deriving from either agriculture, waste, or recycling processes. Such topics are the focuses of the present analysis. Specifically, this paper intends to provide a contribution in the field by identifying new types of environment-friendly composites, containing vegetal matters and ecological waste resulting from recycling activities. Outcomes of a series of performed laboratory analyses concerning the thermal conductivity of four different samples of assemblies, are quite promising and candidate these new composites – albeit further analyses are certainly recommended – as a practicable alternative to the mostly used traditional insulating materials.