Acoustical properties of hemp-clay: from material to wall scale
Résumé
Hemp-clay is a promising materiel dedicated to sustainable building thermal insulation. It brings avery low embodied energy (up to 20 times lower than hemp-lime materials) and can be largelyavailable at a local scale. In the framework of Ecoterra project, special attention is given to theacoustic properties of these materials.A first study has been carried out to investigate the acoustical behavior of this mix at the materialscale. In this work, more than 200 hemp-clay samples were characterized to get a global view ofthe 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 alsobeen highlighted.In order to continue these investigations, studies were then carried out at the wall scale, to testmore representative systems of building envelopes, including coatings effect as well as timberframe effect. A new experimental campaign has been carried out with more than 20 samples(60*60 cm²) using an intensimetry approach. The results give us an interesting visibility on spatialhomogeneity 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 therelationships existing between material and wall scales on the basis of a multilayer modelling, thetransfer matrix method