Mistakes when airing: why does condensation form on the window?

Here's how you can avoid it

Created: 09/01/2023 17:02

By: Helmi Krappitz

Misted windows despite long airing - an energy expert explains why the moisture settles on the windows and what you can do about it.

Rostock – you know it: fogged up windows and no matter how long you air the room, the drops stick to the cold surface.

Condensation occurs more frequently in winter than in summer.

But what is behind it and what can you do about it?

Arian Freytag from the Mecklenburg-Western Pomerania consumer center explains to the dpa how to deal with stubborn condensation.

Misted windows: how does condensation form?

The fogged windows are condensation, which can also drip down.

Condensation forms due to excessive humidity hitting cold surfaces in a room.

These surfaces are mostly windows, but can also be walls.

When they meet, the moisture, which is 100 percent at the point, condenses.

Even if a hydrometer measures a lower humidity elsewhere, condensation cannot be ruled out elsewhere.

To avoid this, you should ventilate so that no moisture damage or mold growth occurs.

Because condensation forms the perfect breeding ground for spores.

Ventilate properly: Wipe the window pane, ventilate, wipe again.

© IMAGO/Michael Bihlmayer

Humid air: when does mold form?

The danger of mold formation already exists before 100 percent humidity.

Because mushrooms can grow from a relative humidity of 70 to 80, explains Freytag, head of the building, living, energy department at the Rostock consumer advice center.

With such humidity, you usually don't see any condensation on the walls and it doesn't feel damp either.

This is deceptive, as the structure of the wall can absorb some of the moisture.

It's different with windows.

Here you can see the condensation earlier.

Humidity: How do you ventilate properly?

The optimum humidity is between 40 and 60 percent - this is usually how you are safe from an infestation.

Freytag recommends airing two to three times a day.

Each for a maximum of three to five minutes.

Wiping damp window panes dry also helps prevent mold.

Ventilating until the condensation disappears from the panes is not worth it.

This is how you ventilate for too long and the heat is withdrawn from the room air and the walls.

Warming up then costs more energy and, above all, money.

According to Freytag, optimal ventilation works like this: First wipe the condensation off the window panes and then air the room.

New hardware enters almost immediately when the window is opened.

When it has disappeared, the window should be closed again.

Finally, wipe the remaining water residue off the pane again - and you're done.