Windows in the attic very wet

Around 45 [So 45] is good in my opinion. Some condensation can still form on the windows if the room cools down at night and especially if the windows remain closed. Right after getting up, open the windows fully for 5 minutes, possibly also create a draft (well, at -10°C maybe just 3 minutes ;)), then a large portion of the moisture is gone. Doing this about 3 times a day would be pretty good. And don’t worry, it doesn’t consume much energy, the room quickly returns to a comfortable temperature…

Ventilate at the top several times until 45-50% is reached and the condensation on the windows is gone. Ventilate in the evening before going to sleep, and do not turn down the heating at night.