Heating in the bedroom: How many degrees are comfortable at home?. According to consumer center.de, “at least 16 degrees” is best.
The Federal Environment Agency recommends opening the windows fully several times a day and ventilating briefly and vigorously for five minutes. Leave the windows tilted at night - but not when the heat is on. You should also make sure there is enough fresh air. Shock ventilation is recommended during the heating season. A tidy and well-kept ambience also generally ensures more well-being.