Multiscale modelling for better hygrothermal prediction of porous building materials

¹ Université de La Rochelle - CNRS, LaSIE UMR 7356, Avenue Michel Crépeau 17042 La Rochelle Cedex 1, France
² LMT, ENS-Cachan, CNRS, Université Paris Saclay, 61 avenue du Président Wilson, F-94230 Cachan, France
³ ENISE, Université de Lyon, LTDS CNRS UMR 5513, 58 Avenue Jean Parot, 42023 Saint Etienne, France

Abstract

The aim of this work is to understand the influence of the microstructuralgeometric parameters of porous building materials on the mechanisms of coupled heat, air and moisture transfers, in order to predict behavior of the building to control and improve it in its durability. For this a multi-scale approach is implemented. It consists of mastering the dominant physical phenomena and their interactions on the microscopic scale. Followed by a dual-scale modelling, microscopic-macroscopic, of coupled heat, air and moisture transfers that takes into account the intrinsic properties and microstructural topology of the material using X-ray tomography combined with the correlation of 3D images were undertaken. In fact, the hygromorphicbehavior under hydric solicitations was considered. In this context, a model of coupled heat, air and moisture transfer in porous building materials was developed using the periodic homogenization technique. These informations were subsequently implemented in a dynamic computation simulation that model the hygrothermalbehaviourof material at the scale of the envelopes and indoor air quality of building. Results reveals that is essential to consider the local behaviors of materials, but also to be able to measure and quantify the evolution of its properties on a macroscopic scale from the youngest age of the material. In addition, comparisons between experimental and numerical temperature and relative humidity profilesin multilayers wall and in building envelopes were undertaken. Good agreements were observed.