Condensation on the window is an indication that the humidity in the room is far too high and that ventilation is urgently needed. Even in freezing temperatures, it is necessary to air every day and even several times – otherwise mold will form in the room. Proper ventilation in winter is possible with little effort – we explain what you should pay attention to.
Whether in summer or winter: You should open the windows briefly several times a day for ventilation – in the middle of a pandemic, of course, even more frequently than usual. If it is frosty-cold outside, but the shock ventilation can be shorter.
Proper ventilation in winter: How many minutes to ventilate?
The association "Window + Facade advises at minus temperatures concretely to a ventilation duration of five minutes. At zero to ten degrees plus it should be ten minutes per airing, at over ten degrees 15 minutes.
Does this apply to all rooms?
How often you should ventilate each room depends on many individual factors. About whether you also stay and breathe in a room. Or sweats in bed at night.
Cooking, showering and bathing are the main sources of humidity. After that – at least in the appropriate rooms – should always be aired directly. In addition, the more people live in the household, the more frequently it should be ventilated.
Why is air exchange so important?
Ventilation is not so much about regulating the temperature, but about, lowering the humidity.
Roughly explained: Warm, heated room air is able to store a relatively large amount of water. When it hits the cooler walls in the room – especially the outer walls of the house – the moist air condenses on them. However, the water film is an optimal breeding ground for mold. Especially in corners of the room, in niches and around the windows, but also behind pieces of furniture directly on the outer wall, the danger is highest.
In addition, of course, fresh oxygen comes into the room when ventilating. And: With the draught of air also (corona) viruses are transported away.
How do I know that the humidity is too high??
The hygrometer, a measuring device for air humidity, gives an indication of when airing is due again. If it shows a value of more than 60 percent humidity, you should open the windows, is the general advice.
But the value also depends on the outside temperature and the insulation standard of the house. On cold days, the upper limit in poorly insulated old buildings can be as low as 40 percent relative humidity, while well-insulated new buildings can easily cope with 55 percent.
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If condensation forms on the window or wall, the humidity in the corresponding places is already 100 percent. But molds grow even at a relative humidity of 70 to 80 percent, explains the consumer center Mecklenburg-Vorpommern. At this value, the surface neither feels damp nor can condensation be seen.
Tip: In Corona times establish themselves increasingly so-called CO2 measuring devices or traffic lights, which are especially suitable for rooms where there are a lot of people. They use tones, readings and/or colors to indicate when to ventilate. Appropriate devices are available from about 50, – Euro.