Effect of airflow velocity on moisture exchange at surfaces of building materials

The moisture transfer between air and construction are affected of the boundary layer conditions close to the surface, which is influenced by the airflow patterns in the room. Therefore an investigation of the relation be-tween the surface resistance and the airflow velocity above a material sample has been performed. The experiments are performed by use of the ordinary cup method for permeability tests. A total of 3 different types of experiments have been performed and for each type different airflow velocities have been tested and compared. As expected the results show that the surface resistances decrease for increasing airflow velocity above the boundary layer of the material surface. The measured resistances are somewhat smaller than the ones esti-mated by use of the Lewis relation.