Hygric properties of materials used for isobio wall solution for new buildings

Abstract

The European ISOBIO project allowed to both develop new bio-based building insulation materials and improve industrial products from the partners of the project. It leaded to several multi-layers solutions to be used as typical wall for new building or for retrofitting. The hygrothermal behavior of these walls is studied experimentally (two demonstrator buildings and one laboratory test-wall) and numerically.

This study investigates the hygric characterization of the materials used to produce the core of the new wall solution: compressed straw board (CSB), commercial oriented strand boards (OSB), soft insulation panels (Biofib trio, CAVAC), rigid insulation panels developed within ISOBIO project (CAVAC panel). This paper presents the methods and the results obtained on absolute and apparent densities, total porosity, sorption isotherm, water vapor permeability at dry point and at wet point, and moisture buffer value. The studied materials are highly to very highly porous (60 to 98 %). They are hygroscopic. Their water vapor resistance factor is low for Biofib insulation, high for OSB and medium for CSB and CAVAC panels. It decreases between dry point and wet point in link with the hygroscopicity of materials. Their MBV gives them moderate to good moisture buffering ability (respectively for CSB and OSB, and for Biofib and CAVAC panel). The study provides an entire set of results that widely characterize the hygric behavior of studied materials and allow to compare them. It underlines very different behaviors, particularly under transient conditions. These data are useful to be implemented in numerical models that simulate hygrothermal behavior at wall scale.