Experimental measurements of the thermal conductivity of insulant elements made of natural materials: preliminary results

Current policies addressing the energy efficiency of building constructions urge planners and manufacturers to properly design the edifice envelope which has to be conceived with a view to both optimizing its thermal performances and complying with the local and national regulations. To achieve this target, for the last few years, researchers involved in building industry have been devising new structures able to realize proper levels of envelope thermal insulation, also employing materials characterized by low environmental impacts owing to their natural origin (such as vegetal fibers) or because derived from industrial/ agricultural process waste. As a contribution to this topic, the purpose of this paper is to assess the insulation features of various structures made up of totally natural and biocompatible materials, in order to try to single out the optimal configurations. The studied mixtures, as a matter of fact, consist of a natural binder (such as hydraulic lime NHL 3.5) and a biocompatible inert material (such as dry platanus acerifolia fruit, natural cork, etc.) with various mass ratio compositions. The measured parameter is the thermal conductivity and the method used is the one stated by the ASTM C518 – 04 Standard, which employs a heat flow meter apparatus establishing steady state one-dimensional heat flux through a test specimen between two parallel plates at constant but different temperatures. Fourier's law of heat conduction is, hence, used to calculate thermal conductivity of the specimen.