Combined heat, air, moisture modelling: A look back, how, of help?

• Review paper covering the field of combined heat, air, moisture modelling.
• Starts with sketching its history from the mid 1930-ties till today.
• Follows a walk along the physics involved.
• Evaluates applicability as basis for correct design and aid in practice.
• Concludes that the art of engineering has still its importance.

Trials to model combined heat, air, moisture transfer in and through building assemblies started in the 1930-ties, when the first methodologies surfaced that coupled steady state vapour diffusion to steady state heat transport. Thanks to H. Glaser and his papers published end of the 1950-ties, that diffusion/conduction approach gained physical correctness. Some 13 years later, capillary suction was added as transport mechanism. At that time, computer software already helped solving models that linked transient heat transport to moisture transfer by diffusion and suction in composite assemblies. Later, air got included as carrier for heat and vapour while increased computer power allowed analyzing two- and three-dimensional geometries. After 2000, the turn from the assembly to the whole building level gained attention.Although the theory looks well established and the computer software, actually available, quite complete, still it does not always help explaining and curing the damage cases, encountered in practice. As built complicates things and physics related pitfalls remain: simulations base on too simple drawings, inability to correctly include airflow, overlooking pressure and gravity driven water flow, uncertainty in material properties, difficulties to grasp the real initial and boundary conditions, the complexity of the envelope/building interactions, etc.