Adequate ventilation in extreme cold: this is behind the 5×5 rule
The rumor has spread that it is better not to open the windows for a long time, but rather open them completely and then ventilate them briefly. This is called intermittent ventilation or, if you open opposite windows, cross ventilation.
In spring or autumn, a complete air change can take 15-20 minutes, and if you do it three to five times a day, the windows stay open long enough. This tactic no longer works in winter because the outside temperatures are too low.
However, it is advisable to ventilate the room as often, that is, even when the temperature is below zero three to five times a day. But then that’s enough three to five minutes with the window open. From there, as a reminder, the 5×5 ruler derivative: Translated, this means broadcast five times a day for five minutes.
It’s easy to keep on vacation or weekends or if you work from home a lot. However, if you’re away from home during the day, you need a different strategy. The good news: if you’re away all day, a less frequent broadcast is enough. Minimum in the morning and in the evening, but it is better to go with the 3×5 ruler. which means Ventilate for five minutes three times a day.
Air out in the morning when you get up from work and just before going to bed.