Better life conditions in modern times have brung with them a life in warm, comfortable and well-insulated facilities what also has its bad sides. Modern windows and doors are hermetic and in that way disable air exchange, i.e. ventilation, due to which water vapor, made during the everyday activities, cannot get out from the room. That leads to the condensation in the glass surfaces and mildew on the walls.


The condensation represents the change of the physical state of matter from gas phase into liquid phase. It appeared when water vapor from the air is in contact with a flat, cold surface where occurs bluring or small water drops. As a consequence of condensation, there is mildew on the window edges as well as on the walls and ceiling.


  • One liter of gas for heating can produce one liter of water vapor
  • Combustion of 1 m3 of fuel in the solid fuel stove causes 0.8 l of water vapor
  • after the construction of new facilities, construction materials, which can absorb to seven thousands liters of water, are dried and evaporated
  • two adults produce about 0.64 l of water vapor for 8 sleeping hours
  • Bathing and laundry washing causes 1.5 l of water vapor on average
  • Drying laundry in the room makes about 5 l of water vapor per day

You should take into account that a double glass is an excellent insulator but is not a heat source. Even in the excellent insulated and heated room, internal glass will be the coolest place which the water vapor makes a contact with, what results in condensation.


Ventilate rooms regularly
Everyday ventilate a room leaving a window in the tipping position. Open the window wide a couple of times during the day for 10 minutes in order to enable the best ventilation of the room, especially when the temperature outside is above 0o C.
Restrict humidity process
If you cook, always use a hood. After bathing always open a window wide in order to get out an excess of water vapor from the bathroom. If you don’t have to, do not dry laundry in closed rooms. If you have to, do it less often.
Radiators and stoves put under the window
If warm air continuously flows through the glass, it is less likely that condensation will occur. This is especially important during the colder weather.
Heating and ventilation
Pay special attention in recently constructed facilities. During dry and warm days ventilate rooms more often and keep the temperature slightly higher than usually.