Numerical simulation programs have been developed recently in order to support the investigation of the coupled heat, air, salt and moisture transport in porous building materials. Without the use of HAM models it is not possible to evaluate the wetting and drying behaviour of building materials exposed to transient boundary conditions. One needs computer models to deal with issues such as shrinkage, swelling, hysteresis, bypass flow, dual porosity, mobile and immobile water, salt transport, and numerous applications related to durability of materials. To this end, however, one needs to develop a simplified but solid foundation of material characterization (engineering model) and select appropriate material properties. The basic criteria for such a selection are :

? Material characteristics must relate to thermodynamically defined potentials (e.g. free energy of Gibbs)

? Material characteristics must be determined in such a manner that introduction of new potential components is possible (freezing depression, osmotic pressure, air pressure, overburden envelope press ure etc.)

? Material characteristics must be determined in such a manner that any modification of the relation between moisture content and total moisture potential is possible (capillary moisture hysteresis)

? Numerical or analytical functions used to describe changes in the material characteristic as a function of degree of saturation must have a reasonable precision and the goodness of fit

? A number of measured points must be reduced to a minimum and those measurements must be relatively easy to perform (i.e., they would not require determination of temporal and spatial profiles of moisture)

This work should be backed by a fundamental level of material characterisation that allows an ?individual description" of material properties by alternative usage of different models. The following paper introduces such an approach that has been implemented in the Material Database of the simulation program DELPHIN4 developed at the Institute of Building Cl imatology.

see also

Bomberg, M., Carmeliet, J., Grunewald, J., Holm, A., Karagiozis, A., Kuenzel, H. and Roels, S., 2002, Position paper on material characterization and HAM model benchmarking

• HAM: material properties
• HAM: simplified models - simplification
• HAM: theory and modelling

1. Documentation of the Numerical Simulation Program DIM3.1, Volume 1: Theoretical Fundamentals
2. Evaluation of discretized transport properties for numerical modelling of heat and moisture transfer in building structures
3. Modified cup for testing of water vapour transmission through thick, permeable materials
4. Numerical and experimental investigation of coupled heat and moisture transport problems
5. On the hysteresis in moisture storage and conductivity measured by the instantaneous profile method
6. Position paper on material characterization and HAM model benchmarking
7. Towards an engineering model of material characteristics for input to ham transport simulations - Part 1: an approach  

1. A comparison of different techniques to quantify moisture content profiles in porous building materials
2. Analysis of selected water absorption coefficient measurements
3. Numerical and experimental investigation of coupled heat and moisture transport problems
4. On the hysteresis in moisture storage and conductivity measured by the instantaneous profile method  

1. Numerical and experimental investigation of coupled heat and moisture transport problems
2. Towards an engineering model of material characteristics for input to ham transport simulations - Part 1: an approach