This study focuses on impact of vapor proofing and airtightness on hygrothermal performance for wooden exterior walls. Partial air and moisture penetration into fibrous insulation layer of the wall were mainly addressed in terms of practical issue for the hygrothermal design. Laboratory experiments using wall assemblies with partial defects for vapor proofing such as outlet were implemented to better understand moisture distribution and air flow within the walls when pressure difference occurs between the indoor and the outdoor rooms. After a developed HAM analysis model was verified by the lab-experiments, long-term simulations were performed to clarify moisture accumulation within the wall under various climate conditions. The simulation results indicated that requirements of both the vapor proofing and the air tightness can be mitigated in mild climate regions. Additionally, the results showed that the partial defect at the top of walls causes the moisture accumulation.
