Before each airing, turn the heating to snowflake.
Underfloor heating is an exception. They can stay on because their thermostat is not close to the window.
Did you already know? After airing, set the rotary valves back to the way they were before. The room will not warm up faster if you turn it all the way up. It only costs more.
Close the door when you are cooking, cleaning or showering. When you have finished: Open the window so that steam and moist air do not remain in the flat.