Monitoring and thermal characterization of flax shives for building thermal insulation

Abstract

This work involves the study of flax shives, natural product derived from the flax production. We want to valorize it as a local resource for thermal insulation of buildings, guaranteeing a low impact on the environment, especially that it doesn’t go through any transformations apart from the addition of a biological fire retardant. Flax shives arise from flax plant that is grown in Western Europe. From retting flax phase to scutching, flax fibers are separated from the stem. When grinding, the central stem is broken into small fragments called flax shives which represent about 50% of flax production. The developed research focuses on flax as additional fiber for cementitious materials such as manufacturing flax concrete blocks. The use of flax in the building sector concerns essentially the insulation. This solution mobilizes the short fiber flax, called tow. The insulation is usually available in soft rolls or semi-rigid panels of wool. Currently, the shives are used as bedding for animals or are integrated in the component mixture of particle board. The main scientific issues related to the study of heat and mass transfer is to determine the evolution of the thermal characteristics of the material and its durability. For a first step, we propose a laboratory analysis of hygrothermal behavior of shives by conventional thermal methods for characterizing thermal conductivity and volumetric heat (flow meter methods), sorption curve is also determined. Then comes the experimental part that involves an independent house in which the old insulation of the attic (glass wool) was replaced by flax shives. We followed the hygrothermal behavior of this new insulation. This work takes place as a part of a project named "Citizen Researchers" of the “Hauts de France” region.