Condensation in a closed cavity double skin facade: a model for risk assessment

Double skin facades are a popular feature in office buildings worldwide, because of their aesthetic, thermal and acoustical properties. This paper discusses a dynamic model that allows the designer of such a facade to assess the risk for condensation in the enclosed cavity between the panes of the facade. Prediction of this risk is crucial because of the associated need for cleaning and accessibility of the cavity. First, the assumptions made for the thermal, airflow and hygric behaviour within the cavity are discussed. Next, the results rendered by the model are compared to those obtained in a full scale test setup. The good agreement demonstrated when hygroscopic behaviour is included yields the conclusion that this model is a powerful tool to describe the hygro-thermal behaviour of the cavity in a double skin facade and stresses the importance of including non-isothermal moisture buffering behaviour in the such a model.