This phenomenon appears mostly in the early morning when the moisture levels where very high during the night.

It’s a result of a high performance double glazing with powerful thermal insulation. These glass surfaces have top quality thermal insulation which prevents the heat transfer towards outside and thus, the outer glass remains extremely cold (especially during the night). As soon as the sun rises and heats the surrounding air, resulting in higher temperature than on the surface of the outer glass, condensation happens and there is a possibility of moisture appearing outside, depending on the orientation of the building and the environment. This phenomenon is not a defect of the double glazing but rather the proof of its excellent thermal insulation! The moisture disappears with the gradual increase of the temperature.

References:
Guardian Europe (Handbook/GB-EU/09-12, p. 44)
AGC (YOURGLASS POCKET/EN/2014, p. 132)

Double Glazing: 4mm ClimaGuard Solar – 90% argon gap – 33.1 laminate clear
U-value: 1,0
Solar Factor: 42%
Light Transmission: 65,2%
Aluminium Profile: MU 2500T (Muskita)
Orientation: Βόρειος