Hygrothermal characterization of a fictitious homogenized porous material to describe multiphase heat and moisture transport in massive historic walls

Abstract

The hygrothermal analysis of historical building envelopes is an important part of renovation concepts for existing buildings. Using dynamic hygrothermal simulation is an effective approach to predict moisture-related damage, such as the risk of mold infestation or susceptibility to frost damage. However, modeling a historic wall of brick / stone and mortar joints with a detailed two- or three-dimensional model is complex and time-consuming. Old masonry is often simplified into a one-dimensional stone / brick layer in hygrothermal simulations, whereby mortar joints are neglected. In a previous work, we identified cases where this method led to unacceptable simplifications. This study presents a method to replace a complex historical masonry (our reference), which consists of different material components with a fictitious homogenized porous material. The aim is to optimize the material properties of the homogenized material so that the behavior of the reference model is well approximated for the most important applications. The method is applied and validated on nine combination of three mortars with five different stones and bricks. Finally, the satisfactory behavior of the homogenized material under dynamic conditions is verified for the praxis example of an internally insulated wall in different climatic conditions by comparing it with its two-dimensional reference model. The improvements in using the developed method with respect to the one-dimensional stone/brick layer approach are considerable especially for hygrometric parameter and are more pronounced the more different the hygrothermal properties of the materials in the reference model are.