Physical model to predict surface condensation on naturally ventilated church windows

In order to protect old leaded windows of historical churches against corrosion hy acid rain, air pollution and vandalism, protective glazing is placed at the outer side of the original windows. An extra advantage is the smaller heat loss by transmission. Situating the protecting window at the outer side of the original window induces an extra possihility for surface condensation. Depending on whether the cavity is naturally ventilated with warm indoor church air, or cold outdoor air, surface condensation may occur on the outside protecting glazing or on the inside original glazing. This contribution describes a developed computer model to predict the prohability of surface condensation on the original or protecting glazing. The modeI was validated by measurements at an experimental mouel in a so called hot-hox amI by in situ measuremellts in a church in Gennany.