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Heat, Air and Moisture (HAM) modelling of building performance is a quite young research subject but the experimental determination of 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 HAMtransport simulations. The paper presents such an approach, called an engineering model for hygrothermal material characterisation.The paper poses the question, how to arrive at input data that can be used for a model based on thermodynamically defined potentials (Only such a model allows introduction of new potential components (freezing depression, osmotic pressure, air pressure, overburden envelope pressure)) (e.g., Grunewald, J. (1997) and Grunewald, J. (1999)) and yet the respective functions used to describe changes in the material response as a function of the variables of state. Such functions should have a reasonable precision and goodness of fit while the number of measured points must be reduced to a minimum. Those measurements should be relatively easy to perform (i.e., they would not require determination of temporal and spatial profiles of moisture).

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The erection of new buildings, the renovation and preservation of building structures and monuments requires the quantification of the temperature, moisture, salt and pollution distribution in porous materials. The thermophysical modeling leads to a coupled nonlinear differential equation system. The temperature T and the capillary pressure pc will be used as driving potentials in this transport system. The air and salt transport and the crystallization and ice forming have been neglected in this paper although this processes have been formulated, too. In order to solve the transport equation system with modern numerical methods the material functions thermal conductivity λ(w( pc),T ), capillary conductivity K(w( p c),T ) and vapor conductivity δ(w( pc), T ) and the moisture retention function w( pc,T ) are necessary. This paper will be focused on the determination of w( pc) and K(w( pc)) in the isothermic case. The results will be compared with measurement results of the capillary active insulation material ``calciumsilicate''.