I hadn't had a problem with humidity until our recent arrival of winter (-10). Windows were sweating profusely. Changing the furnace fan to run continuously made a HUGE difference. Colder out now (-15), and there is very minimal condensation (about 1" on the bottom of the windows only, where they were completely covered before.

Probably not the ideal permanent solution (I am going to look at a HRV), but I think this will get me through this winter.