Natural and waste materials as building insulating elements: experimental measurements of thermal conductivities

Current policies addressing energy efficiency of buildings and the need to control the overall primary energy demand, imply not only that the edifice envelope has to be properly designed, with a view to optimizing its thermal performances, but also that the ecological properties of the building materials have to be considered for the whole assessment of the involved environmental costs. To achieve this target, for the last few years, researchers concerned with 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 fibre) 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 biocompatible inert materials (such as dry platanus acerifolia fruit, natural cork, etc.) diversely assembled. The measured parameter is the thermal conductivity and the measurement method employ a heat flow meter apparatus which, complying with the ASTM C518 – 04 Standard, is able to establish and assess the steady state one-dimensional thermal transmission through flat slab specimens.