When the glass gets cold enough it will draw moisture from the air, just like condensation on a glass of iced water. This doesn't imply that the windows are bad, just cold.
Modern buildings are sealed much better than old older buildings. This is generally a good thing, but one of the problems is that it is harder to get rid of excessive humidity.
This condensation can cause problems such as mold, mildew, and/or damaged paint.
To help with this you need to reduce the humidity inside your home:
- Use exhaust fans to vent steamy air during (or after) running the shower
- Similarly, if boiling water on the stove, use a hood vent (or open a window)
- Make sure your clothes dryer's vent hose isn't leaking warm moist air into your house.
- If these aren't sufficient, buy a dehumidifier
A relatively inexpensive dehumidifier simply sits in the corner and collects water from the air. The water collects in a reservoir, which you have to empty regularly. However, I would highly recommend installing a drain hose. It's amazing how much liquid can be gathered in just a few hours!