Ventilate in very cold weather: this is what the experts recommend…

Brrr, it’s freezing cold outside right now. Even if it is not very welcoming: you still need ventilation, especially in winter. But how often and for how long should you ventilate when it’s cold? Here are the most important rules.

A household of four people releases between six and twelve liters of water into the air per day, which is almost unimaginable. This quickly explains why it is necessary to ventilate regularly – especially in winter. Warm air in living spaces can absorb more humidity than cool outside air. It is therefore more humid – and regular exchange through ventilation is important. The air should be completely changed at least three to four times a day – especially if you are at home all day.

How does good ventilation work when temperatures are negative?

In winter, three to five minutes of intermittent or cross ventilation are sufficient when the outside temperature is low or there is wind. “Contrary to what is often feared, interior walls are hardly cooled by careful thorough ventilation,” explains Frank Lange, director of the German association Fenster + Fassade (VFF). In detail, the association recommends:

  • Temperatures below 0 degrees Celcius: If it’s colder than 0 degrees Celsius, you should only open the windows for 5 minutes.
  • Temperatures between 0 and 10 degrees Celcius: at these temperatures, it is sufficient to ventilate for approximately 10 minutes.
  • More than 10 degrees Celcius: If the temperature is above 10 degrees, the windows can be opened for approximately 15 minutes.

After sleeping or cooking: Open the windows!

The best time to ventilate also depends on the room and its use. After showering, bathing, cooking or sleeping, the humid air should be immediately renewed.

Just after getting up, you should ventilate the bedroom well. “Then, during the day, heats to a temperature of at least 16 to 18 degrees Celsius,” continues the consumer association: “The higher the air humidity and the lower the ambient temperature, the greater the risk of mold is important.”

Frequent ventilation is in any case necessary when drying laundry in the apartment, whether on the drying rack or in the dryer. Many plants and aquariums are also sources of humidity – in this case you should also ventilate more often.

A healthy living climate is achieved by finding a suitable ratio between temperature and air humidity: Depending on whether the residents are sitting on the sofa or working in the household, the temperature should be between 18 and 22 degrees Celsius and relative air humidity between 40 and 60 percent.

Consumer protection associations recommend using a hygrometer to measure the humidity in the air in the room. Hygrometers can be found for a few euros, they can help to correctly regulate the humidity of the air.

The level of air humidity depends on the condition of the building and the outside temperature: In a well-insulated building, a value of around 60 percent in the apartment may not pose a problem “for a time “. If the building is poorly insulated, 40 percent at thermal bridges and in room corners may already be too high in cold weather.

Open the windows – even when temperatures are negative

“The important thing for good ventilation is to open the windows completely,” explains VFF director Lange. Constantly remaining “on the tilt” cools the parts. He advises: “During ventilation, radiators should be turned down, either manually or through automatic heating valves, which can be installed easily and inexpensively.”
Combine different ventilation modes

Opening the window several times is sometimes not enough to get rid of moisture accumulated in towels, duvets or wall and furniture surfaces, according to experts from the consumer association. Regular air exchange after forced ventilation can be supported, if necessary, by a ventilation system, such as an exhaust air system in the bathroom.