Condensation forms wherever warm moist air comes into contact with cold surfaces. Due to their nature and location, roof windows can be more susceptible to condensation, which, if it occurs, is a sign of excess moisture within the room.
The best way to reduce condensation is to have a fully functional ventilation system. In order for the ventilation system to work properly, a constant access for fresh air through windows and air inlets must be ensured. Condensation can also be limited by careful use of heaters (directly beneath the window), and by installing linings beneath vertical combination windows. When a window cill is in place beneath a window, a gap should be kept between the cill and the wall, in order to provide proper air circulation.