Condensation, set this temperature of the radiators and it will no longer be a problem

Use a dehumidifier

Another way to avoid condensation on the windows is to use occasional ventilation , or a dehumidifier, an ideal device for sanitizing the house whenever you want and to use for as long as you want.

You can program it and make it work at pre-established times , obtaining excellent results. The dehumidifier condenses water vapor, recovers it in a liquid state and allows you to face the winter season without the risk of condensation humidity.