When it comes to windows, there is a type of sealed unit of windows commonly known as double glazing. Just like the word suggests, it perimeter of this window is usually sealed thus trapping the air that is found between the panes. Unlike other types of windows these types of windows have insulating qualities that is brought about by the air trapped inside. Overtime you may be requires having double glazing repair to the windows because of the wear and tear that occurs to the windows resulting from expansion and contraction of air.
Once the seal breaks, the continued contraction and expansion of air leads to infiltration of the moisture. This moisture then evaporates then it gets some heat and later condenses on the cold glass. If not taken good care of early enough, it can get worse with time.