Towards an engineering model of material characteristics for input to HAM transport simulations

The experimental determination of hygrothermal material properties is often based on classical methods. One should review the manner in which we define characteristic material parameters and there is a need to develop an approximation used to generate the required material functions for input to simulations. The paper presents such an approach, called an engineering model for hygrothermal material characterisation. The critical element of the proposed approach is the relation of two primary material characteristics: moisture conductivity and moisture storage to the pore structure of the material. Moisture retention curve is established by a few measurements in hygroscopic and above hygroscopic regions. Heat, air and moisture transport (HAM) models are increasingly applied to assist in evaluation of the hygric behaviour of building materials and structures. One can classify the HAM models into three groups: the simplified, engineering and research models for hygrothermal material characterization. The experimental determination of hygrothermal material properties is often based on classical methods. The most important material characteristic is the moisture retention curve (MRC) or moisture capacity. A precise characterization of the MRC implies not only an accurate description of moisture storage, but also the possibility of generation of transport characteristics through pore/network models and enhanced precision in transformations between liquid water conductivity and diffusivity.