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Необязательно, может просто брак. Тут был случай, когда на жилой высотке стекло в ограждении балконов вообще без причины разбивалось. Импорт откуда-то. Вроде как-то неправильно его закалили, или ещё что-то, в общем брак, так что наверно даже перепадов температур хватило для разрушения. Может как-то так получилось и с субжем.
з.ы. Вот кое-что:
Shattered glass: what causes panes to fall off buildings - Canada - CBC News
"The amount of stresses generated simply from hot versus cool is not enough, I don't think, to induce the kind of fractures we're seeing."
"I think it's more likely this glass has impurities, and the most likely culprit is something called an inclusion that [is] the result of the glass manufacturing."
"That's a process that involves heat treatment and needs to be done properly to essentially build stress into the glass to help strengthen [it],"
If the glass is not treated properly, the internal, or residual, stress of the glass will be too high and, coupled with the unavoidable imperfections, will result in spontaneous, also known as delayed, fractures that grow over time.
И т.д.