This paper investigates the airtightness of a wood-frame passive house during the consecutive construction stages. Aim is to investigate whether an acceptable airtightness can be achieved by the external wind barrier only. The wind barrier consists of a promising new type of asphalt impregnated fibreboards. To quantify the different leakage paths, the study applies the reductive sealing technique. In total 12 pressurisation tests have been conducted during the construction process. In addition to these field tests on the entire building, the paper discusses the results from laboratory measurements on specimens of the wind barrier including typical joints, in order to verify the influence of different possible types of local air leakage paths. The results reveal that the external wind barrier has a significant airtightness. Moreover, by sealing only the most critical joints of the outer shell, the overall airtightness of the studied case fulfils the requirements of the passive house standard (less than 0.6 air changes per hour (ACH) at 50 Pa). The results presented in this paper, thus, indicate that the proposed solution may have potential to reduce the labour costs required to reach a sufficient level of airtightness. (C) 2010 Elsevier B.V. All rights reserved.