Understand, first, what is causing the condensation, and you'll be well on your way to 'fixing' the problem! :-)
In short, warm, moist air is condensing on your cold windows. That's really the long and short of it. Eliminate or dramatically reduce the moisture in the air, and you SHOULD be just fine. If your home is real tight, then even the moisture from the kitchen or upstairs bathroom will affect the situation. If opening the windows helps alleviate the problem, then you can see how getting the moisture out of the air (via opening the windows) is working.
I'd hold off with installing fans and opening windows at night too. Check to see if your neighbors have dehumidifiers either free-standing or incorporated into their Heating and Ventilation system. Well, for all I/you know, they run their stove fan and/or bathroom exhaust fan all day! This is certainly not the appropriate long-term solution. There are a number of 'devices' on the market that measure the humidity in the air. One that's low cost, small, and quick is a Capacitive Humidity Sensor. Try an Electronic Shop or hobby store for something. Remember, warm, moist air + cold surface = condensation.