Several research projects have already indicated the importance of airflow and air leakage when considering hygrothermal responses of building components. In order to study the influence of airflow on the hygrothermal behaviour of lightweight wall structures, a test-setup has been constructed at the K.U.Leuven Vliet test building. A terraced house has been built up. First measurements are carried out on the ground level part. The test-setup has two outer walls. The SW-wall is a cavity wall with a plaster finish on the inside. The NE-wall consists of three separate wall-sections, each with different air tightness. Measurements are carried out on the NE-walls, in order to evaluate the influence of air tightness on the thermal and hygric performance of the walls. These walls are subjected to an exfiltration airflow and thus have a higher risk of internal moisture problems. Variations in the test-setup are made by adding extra infiltration and exfiltration openings, thereby influencing the airflow pattern in the test-house and the NE-walls. Furthermore the impact of minor perforations, imperfections in construction but also the influence of wind speed and wind direction are studied.