Cold cracking
This sometimes quite shocking occurrence of double glazed sealed units exploding most often happens in the U.K. between around late October, and early February, but mostly in late December – middle January.
An inner pane in a sealed unit can be the one to suffer breakage. This happens when the inner glass is warmed from the heating in the home, and the outer pane of a double glazed sealed unit is cold from a drop in outside temperatures. In addition, an outer pane can also suffer breakage. This happens when a cold outer pane is warmed quickly by the sunlight bearing on it. The pane of glass subjected to the thermal stress cannot cope beyond a certain amount of deflection. This then results in a sudden crack along the whole length of the unit. Hence, this is always along the long length. Alternatively, it can suddenly shatter altogether. This is known as cold cracking
Double glazed sealed units that are relatively a lot wider in size than their height are most at risk. Also, it seems that units facing certain directions suffer more than others. On sealed units that are a lot squarer, the glass is able to flex more, and in both directions, before it would break.
