Yes, Windows constructed with tempered glass may have a permanent bow due to the tempering process. Bowing of the glass from tempering can be significant, with as much as a 1/16th of an inch per foot of glass. The bowing will remain regardless of whether the unit has pressure equalized.
There is no current solution for this problem and the homeowner should be aware that the windows with internal bars (shadow, muntin) and tempered glass could have an objectionable gap, which is not considered a defect, between the bars and glass.
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