ᐅ Windows are becoming damp on the inside—what can be done? Older building (built around 2000)

Hello,

we have purchased a house built in 2000, energy certificate class C, constructed with Ytong masonry, and double-glazed windows.

Our problem:

The windows in the kitchen (external corner wall) always get damp in winter (condensation collects on the edges).
However, this only happens in the kitchen; the living room, children’s room, bedroom, and other rooms remain more or less dry.

Of course, I understand that this is caused by the temperature difference between the window glass and the indoor humidity.

But what can be done about it, apart from ventilating properly and heating well (which is not exactly ideal for the heating bill in freezing temperatures)?

We have considered installing triple glazing, at least in the kitchen... but then the question arises whether this might lead to mold growth on the wall with the existing masonry?

Are there any experts here who can help us with:

- From which U-value of the exterior wall is it safe to install triple glazing (meaning, when the temperature difference between the wall and the window on the inside is roughly equal)?
- Why does condensation occur in the kitchen, but not on the other windows in rooms with external walls?
- Could the windows be defective?
- Is it advisable to install triple glazing only in certain rooms?
- When installing triple glazing, is it necessary to integrate ventilation for moisture into the wall?
- Do you have any other suggestions?

Thank you!

roadrunner88 schrieb:

What can you do about it besides ventilating and heating properly (which isn’t necessarily great for heating bills at below-zero temperatures)?

Actually, that is exactly the right solution during cold outdoor temperatures.

roadrunner88 schrieb:

We have considered installing triple-glazed windows, at least in the kitchen... but then the question arises whether the existing masonry might cause mold to form on the wall (or could cause it)?

It can, but it doesn’t have to.

roadrunner88 schrieb:

- From which U-value of the exterior wall can you safely install triple glazing (meaning the temperature difference between the wall and the window on the inside is roughly the same)?

Basically, this is possible with almost all exterior walls. The glazing itself is not the problem, but the airtightness of new windows is. Ventilating and heating are then extremely important. Given your construction year, I assume the house is already quite airtight.

roadrunner88 schrieb:

Why does the kitchen window fog up, but not the other windows in rooms with exterior walls?

Cooking causes high humidity, combined with insufficient heating and ventilation.

roadrunner88 schrieb:

- Could the windows be defective?

Crystal ball says: no idea. Probability says: no.

roadrunner88 schrieb:

- Is it recommended to only install triple glazing in certain rooms?

It doesn’t matter.

roadrunner88 schrieb:

- When using triple glazing, is it absolutely necessary to integrate a moisture ventilation system into the wall?

See above. The type of glazing doesn’t matter. You should follow the same measures even with new double-glazed windows.

roadrunner88 schrieb:

- Any other ideas?

No.

Personally, I would focus on more frequent ventilation and heating. Start by measuring the indoor temperature and humidity. If possible, supplement this by measuring wall temperature with an infrared thermometer.

roadrunner88 schrieb:

We have considered installing triple glazing, at least in the kitchen... but then the question arises whether this might lead to mold growth on the wall due to the existing masonry?

If I were to calculate internally what heating costs ventilation causes and what the triple-glazed windows cost to purchase and install, I’d assume—even without relying on a crystal ball—that you could ventilate for a very long time before coming anywhere close to the costs of replacing the windows...

Ventilate and heat properly, and everything will be fine.
Calling a house built in 2000 an old building is also quite bold...

roadrunner88 schrieb:

Windows in the kitchen (external corner wall) always get damp in winter (condensation forms around the edges).
But this only happens in the kitchen; the living room, children’s room, bedroom, etc. all stay more or less dry.

This is a completely normal and non-critical issue. Warm indoor air in the kitchen can hold a lot of moisture. If the windowpane’s temperature is lower than the dew point, condensation will form on it. The fact that this does not happen evenly over the entire glass is due to air movement in the room. Where the air “stagnates,” moisture settles more quickly.
Basically, you have three options:
1. You can ensure a warmer glass surface. This is the effect of double or triple glazing—the inner pane cools down less.
2. You can increase air circulation near the window. When there is airflow, the condensation effect on a surface is reduced. This principle is used in the ventilation of cabinets.
3. You can remove moisture from the room by ventilating. Moist, warm air goes out, cold air comes in. This works even if it is humid outside because cold air holds less water mass, and as it warms up inside, the relative humidity decreases.
Therefore, ventilation is a good solution. Shock ventilation (opening windows fully for a short time) is more energy-efficient than the commonly used tilt window method, since shock ventilation removes less heat from furniture and objects in the room.

In the 2000s, it was common to install radiators below kitchen windows. If you have one and the area is sealed off by kitchen cabinets, ventilation grilles above the radiator under the window can help to warm the area and promote air circulation as described above.

SoL schrieb:

Calling a house built in 2000 an old building is quite bold...

52 years too late to be considered an old building.

Jesse Custer schrieb:

If I were to calculate internally how much ventilation costs in heating expenses and compare that to the purchase and installation cost of triple-glazed windows, I would assume (even without a crystal ball) that you could ventilate for a very long time before you even come close to the cost of replacing the windows...

Apart from the fact that double glazing (which I prefer to call cavity glazing) is by no means inherently outdated, individual glass panes can definitely be replaced without removing the entire frame.

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