Now that the temperature outside has dropped, the windows start to accumulate water vapor. I am assuming that it might also lead to that black stuff forming. Is there a more efficient way of dealing with the condensate than wiping it dry every day?
These are common in the US. IDK how common they are in Europe.
We have roller shutters. . Way better. Those obviously block the light, but since it's coldest at night and nights in winter are long they help a lot.
But, just like with storm windows it's not necessarily allowed to add those due to zoning laws and landlords.
In any case, if you're ready to spend money and alter your building, then just buy new windows. New windows in Europe typically have at least three panes and a metal layer against infrared.