ᐅ The roof window experiences heavy condensation, with a significant amount of moisture forming in the morning.

In an older attic apartment, there is always the problem in winter that the skylight window sweats heavily overnight.
In the morning, the glass and frame are very wet.
This probably happens because the glass is cold while the room temperature is higher.
Room temperature is about 18°C (64°F).
The skylight window is additionally covered from the inside by a blackout roller blind. There is about 25 cm (10 inches) of air between the blind and the glass.
The room itself is small, about 6 m² (65 square feet).

Does the window sweat so much overnight because the blind separates the skylight glass from the room air?

Using blackout is necessary because otherwise, it would be too bright (street lighting).

Thank you very much.

Insufficient ventilation.

Mycraft schrieb:

Not enough ventilation.

Of course, ventilation takes place in the morning, at noon, and in the afternoon. But not during the night.

6 m² (65 ft²) of space and your breathing air is too much.
You can leave the door open, keep the heating on, or leave the window open for ventilation or tilt it.

Nida35a schrieb:

6 m2 (65 ft²) room and your breathing air is too much,
You can leave the door open, or keep the heating on, or leave the window open on ventilation or tilt mode

No, opening the window or tilting it at below freezing temperatures...
In winter, even the lower edge of the windowpane where the seal is located freezes.
The heating is on low at night. That’s why it’s 19 degrees (66°F). The door is always open.
So the blind (25 cm (10 inches) away from the window) does not cause any issues with air circulation? The blind must remain closed though.

We had the same issue in our previous house. In winter, the skylight would get wet or even freeze around the edges during severe frost. The glazing was only double-pane. However, it was just a heated storage room of about 10 m² (110 sq ft). My solution was a simple small fan (not a heater fan!) that constantly blew air toward the window. That helped.