ᐅ New Window Pane Cracked – Possible Causes?

Thank you for your responses.
My children did not place anything against the window (double-glazed), I do not have any internal blinds, so there is no heat buildup, no partial shading, and no glass insurance.
The old wooden windows lasted for over 40 years without temperature fluctuation issues; they even survived the Lothar storm.
Could the cause of the damage in the new windows be improper installation, a manufacturing defect, or something similar?
Is it possible that the external glass pane will break soon as well, perhaps when I am at work, on vacation, or during the next major storm?

Hello everyone,

We also experienced a thermal crack on a fixed glazing panel nearly 2m (6.5 ft) in size.

We built with a general contractor. Are glass components also covered by the 5-year warranty, or am I just out of luck in this specific case?

Does anyone have experience with glass breakage, warranty claims, and general contractors?

Thank you

You mentioned a fixed panoramic glass panel. In my opinion, it is quite possible that the glass was under stress because the frame was not installed correctly (not square, misaligned).

Possibly a stress crack caused by loads transferred from above through the frame (and glazing)? (i.e., incorrect installation or measurements)

allstar83 schrieb:

We also had a thermal crack in an almost 2m (6.5 ft) large fixed glazing.

We built with a general contractor (GC). Are glass components covered under the 5-year warranty as well, or am I just out of luck in this particular case?

Does anyone have experience with glass breakage, warranties, and GCs?

I have personal experience with a crack in a pane – but it wasn’t handled through the GC/window installer (they went bankrupt). In my case, it was covered through household insurance (glass breakage included). Maybe that could be an alternative.

Otherwise, in my opinion, it’s difficult to claim this under warranty because you first need to prove the crack was caused by stress (incorrect installation, excessive load) rather than a thermal crack (“something was probably placed in front of it”). That’s at least how I would approach it as a GC.

I can only report that the exact same thing happened to us, but in a small triple-glazed window sash—and shortly after installation. Two days after installation, a crack appeared “out of nowhere,” even though nothing was placed against it or exposed to excessive heat. Reporting this to the window manufacturer led to an immediate replacement of the glass by them. It was apparently a material defect, which can happen. Whether this actually helps, I don’t know; it depends on the contractor’s understanding and goodwill. It’s similar to mold in a rental apartment: the landlord knows about the thermal bridge—or just blames incorrect ventilation. Both are difficult to prove, but the latter is easier initially to avoid responsibility.