Aluminum-wood triple-glazed window with internal condensation despite the warm edge

Hello everyone,

as some of you have noticed, I am currently paying a bit more attention everywhere and today, at -15 degrees, something caught my eye.

A few windows have developed condensation on the inside at the lower corners, despite low indoor humidity of 40% and controlled residential ventilation.

The windows are aluminum-wood, triple-glazed with warm edge, part of a KFW55 house.

Is this a defect or unavoidable and acceptable given the outside temperatures? I am surprised that out of 20 windows, only 4 are affected. Personally, I also find that if you put your finger in the corner, you can almost feel cold air through the seal.

Would it be appropriate to demand a pane replacement from the window supplier?

I have attached a picture for you.

I don't know enough about it, but I'm sure the experts like can definitely say something about it. However, I agree that if it only happens with 4 windows, something must be different with them. A little anecdote about this: I store sparkling water on the balcony in the winter, and during the long period with -10 degree night temperatures, it tends to freeze sometimes. Interestingly, not every bottle in a six-pack does. It also doesn't depend on the proximity to the wall unit. I assume that some bottles are simply tighter than others and therefore freeze later...

Hi,
have you ever measured the temperatures of the panes? If the gas filling of the panes is not okay (or their sealing is shot), the panes could already insulate worse.
But it could also be that you have slightly higher humidity in these rooms than in the others. We also have a controlled residential ventilation system, and there is indeed a few percentage points difference there.
Or the wind is hitting the panes, and due to the wind chill, it is considerably colder outside than -15 C.

Best regards,

Andreas

Is the pleated blind always completely closed at the bottom? We had that in our old apartment with the skylights in the bathroom, where there was often condensation behind the pleated blinds. We then always left a gap open at the bottom, then it was better. But whether that is allowed with new triple-glazed windows, no idea... it also seems strange to me, we haven't had this problem anywhere else so far.

... A few windows have condensation on the inside at the lower corners, ...

The same thing happened to me with two small windows, where it was below -20 °C yesterday. The windows are each in storage rooms that are not heated and refrigerators stand under the windows ... Coincidence? Today nothing can be observed.

A few windows have developed condensation on the inside at the lower corners, [...] Is this a defect or unavoidable given the outside temperatures and therefore acceptable? I'm surprised that out of 20 windows only 4 are affected. Personally, I also find that when you put your finger in the corner you can almost feel cold air through the seal. Would it be appropriate to demand a glass replacement from the window supplier?

As I read the picture, "inside" here only means the room side of the panes, not inside the glass unit. So no glass replacement. But probably seal replacement: it looks as if the seals in the corners were not cut at miters but rather bent. I would not deny it as a defect in this respect. It is always soothing to my soul to see that other window manufacturers work just as "pragmatically" as "my" guys did back then ;-)