Material and wall scales investigations on the acoustical properties of light earth (hemp-clay)
Résumé
Hemp-clay is a promising material dedicated to sustainable building thermal insulation. It brings a very low embodied energy (up to 20 times lower than hemp-lime materials) and can be largely available at a local scale. In the framework of Ecoterra project, special attention is given to the acoustic properties of these materials. A first study has been carried out to investigate the acoustical behavior of this mix at the material scale. In this work, more than 200 hemp-clay samples were characterized to get a global view of the acoustical performances of such materials. In addition to that, the unusual multiscale behavior, the poroelastic dissipation, and the first order effect of hemp concentration in hemp-clay have also been highlighted. In order to continue these investigations, studies were then carried out at the wall scale, to test more representative systems of building envelopes, including coatings effect as well as timber frame effect. A new experimental campaign has been carried out with more than 20 samples (60*60cm2) using an intensimetry approach. The results give us an interesting visibility on spatial homogeneity and sound transmission loss levels as a function of various parameters (thickness, density, manufacturing process, coatings and frame existence). The purpose of this presentation is to discuss the main results of these studies, and to draw the relationships existing between material and wall scales on the basis of Biot model coupled with the transfer matrix method.
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