- Turn off your furnace's humidifier. Because adding water to the air will cause this.
- Get rid of the humans. Their breathing, bathing and cooking add moisture.
Between the two, they are the source of this.
The deal is that relative humidity is a different thing than absolute humidity. The difference is, warm air can hold a lot more moisture than cold air.
You are heating your air, greatly increasing its capacity for moisture. You are then adding moisture by breathing, bathing, cooking, or by running a humidifier if your furnace is equipped with one. That greatly increases the absolute humidity in the air, and it can hold a lot because it's warm.
Then, the warm air gets near the window, and chills due to contact with the window. This now-colder air has less capacity to hold moisture, it is driven above 100% humidity so it must condense.
Your house slowly interchanges air with outside through normal leaks (that's why you don't get CO2 poisoning) and it ejects warm, humid air, and intakes subzero, fantastically dry air. Newer homes are much less leaky.
In this case you only want to heat your home enough to keep the pipes from freezing, and you want enough exchange to eject your wet air and admit cold, very dry air. With you not adding any new moisture, window condensation should stop happening.