Importance of a Proper applied Airflow in the Façade Air Gap when Moisture and Temperature are Calculated in Wood Framed Walls

The airflow in the air gap behind the façade panel has shown to be of importance when risks of moisture and mould damages in wood frame walls are calculated. This study demonstrates the importance of a properly applied outdoor air flow in the air gap behind the façade panel when temperature and moisture conditions are calculated. The paper present and compare how variations in airflow in the air gap influence temperature and moisture conditions in a modern Swedish wood framed wall. Different references present various air flows that are adapted in the air gap. Calculations are made in the one dimensional temperature and moisture calculation program WUFI 4.2. The results shows that the air flows in the air gap behind the panel affect relative humidity in all positions outside the vapour retarder. At the same time temperature in the whole construction and relative humidity inside the vapour retarder is not affected by different air flows in a significant way. The conclusion is that a correct airflow in the façade air gap is of importance for calculated moisture conditions in modern Swedish wood constructions. An incorrect air flow can also give significant errors for calculated moisture conditions.