I have a Schüco aluminum window installed in my living room about 2 years ago. Since the beginning of October there's always condensation between the panes, even when it's not that cold. The humidity in my house is normal, I have ventilation. Is this a window defect or is it just because of the changing weather?
Condensation between the glass panes is a sign that the window's sealant may be compromised, allowing moisture to enter the sealed space! With a Schüco that's 2 years old, this should still be covered by warranty, so my advice is to call their technical support to assess it. It's possible that the fall temperature and humidity shift is just revealing a problem that already existed, but quality windows shouldn't do this even with climate variation. If you're sure your house's ventilation is ok (air circulating well, no mold in corners), it's definitely worth getting an inspection because this isn't normal for a recent window.
Condensation between the glass panes is a sign that the air chamber seal has failed, and it's not normal even with temperature changes. If it started recently after 2 years, it could be a manufacturing or installation defect that's showing up now, so it's worth calling Schüco to check the warranty. Changing weather contributes to speeding up the problem, but a window that's working properly won't accumulate moisture inside the double glass even in autumn.
The problem you're describing isn't normal, even taking seasonal changes into account. When the air between the panes starts to fog up, it means the hermetic seal of the chamber has failed and moisture has penetrated that insulated space. It's not a matter of poor ventilation in your home or high relative humidity - it's a specific defect in the window. Schüco is a serious brand and their windows come with a warranty, so you have the right to claim it.
Before contacting the manufacturer or installer, take a clear photo of the fogging during the day (preferably during a colder time) and note exactly when it started. This helps prove the defect and speeds up the process. One thing nobody usually mentions: if you manage to drastically dehumidify the room for a few days (with a dehumidifier or air conditioner in dry mode), the fogging may seem to improve temporarily, masking the problem - but it won't actually solve anything. This is just useful to test whether it really is a seal failure.
Since the window is 2 years old, it should still be covered by the manufacturer's warranty. Contact Schüco directly or whoever installed it, showing the photos and making it clear that the problem appeared spontaneously. They usually sort this out without too much red tape when it's a proven factory defect.
Have you already tried drying the window thoroughly and then closing all the open windows in the house for a few hours to see if the condensation persists? Because if it disappears, it's just air humidity. But if it stays there between the panes, then that's a serious problem.
When the air chamber sealant fails (and with 2 years on a Schüco that's rare, but it happens), moisture gets into that space and gets trapped there - there's no way for it to get out, so it fogs up constantly. That's a defect, not a seasonal thing. The good news is that at 2 years old a window like that should still be under warranty, so contact whoever installed it or Schüco directly to file a complaint. Don't try to mess with it yourself because anything you do could void the warranty.
One thing nobody mentions that's really simple: put some moisture absorbers (those silica gel packs they sell at hardware stores) near the window during the day to see if it reduces the fogging while you wait for the technician. It won't fix the actual problem, but at least it gives you a better idea of whether it's just humidity circulating or if water is actually getting into the sealant. Also open the windows in other rooms a lot to create airflow - sometimes the room gets too closed off and moisture builds up.
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