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In this paper, a double-skin steel building-demonstrator, set up using panels of five bio-based insulators and a classical mineral insulating material, is studied. The panels used in the demonstrator are made from industrially manufactured and commercialized bio-materials. To assess the suitability of these panels for use in cold formed steel envelope buildings, their advantages and/or the drawbacks (if any) of the synchronized records of temperatures, relative humidity and thermal flux of each panel are obtained using a system of continuous measurements. Data from 6 months of records in the roof of the demonstrator are used to assess the infield properties of the panels and the seasonal evolution of these properties in relation to the presence of the vapor barrier. The thermal resistance of each panel is determined from these data using two methods: the ISO 9869-1:2014 based on the Heat Flow Meter (HFM) method and an inverse problem identification method. All bio-sourced panels manifest higher thermal resistance than the classical insulation system, whatever conditions of use with or without barrier vapor. The seasonal variations of thermal properties are attenuated when a vapor barrier is used. No risk for water condensation inside the bio-insulations is revealed so far.

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The use of bio-based composite as building materials is one of the innovative solutions for dealing with environmental disorders caused by the construction sector. Among these materials we find biocomposites based on vegetable aggregates, which have proven their effectiveness as insulating materials in numerous studies. Despite the growing interest in these materials and the recognition of their performance, their use remains hampered by the lack of implementation rules specific to these materials to move towards a control of their use and their durability affected by the climate and use conditions to which they will be exposed at the level of a building. The objective of this work is to study the compatibility of a protective coating with a block substrate of biocomposites based on cereal straw. It is in fact a mixture of vegetable aggregates (straw), a binder composed of lime and additives also obtained from a renewable source (Ismail et al., 2020). These additives (air-entraining agent, casein protein and a biopolymer) have been added to improve both the fibre-binder interface and the porosity of the binder. The use of these bio-based materials for external or internal thermal insulation of the building requires the application of a coating to protect them against climatic aggressions and to give them an aesthetic appearance. The lime-based coatings, air-entraining agent and casein protein selected for this study have been the subject of an experimental investigation (Brahim Ismail, 2020). In order to assess the compatibility of these coatings with the straw-based insulating material, we were interested in studying the adhesion between the biocomposite and the coating after aging cycles in accordance with the EN 1015-21 standard. The samples (biocomposite + coating) were subjected to two types of aging, one using water and the other using a saline solution of sodium sulphates (Na2SO4). The results of the bond tests after aging showed that the cohesive fracture (at the level of the substrate) is a pattern observed in all the studied systems. In Addition, It has been found that the coating to which a percentage of fine fibers has been added undergoes considerable degradation after aging with salt solution, demonstrating the need of an additional layer of outer coating without fibers in order to ensure the sustainability of the system.