The outside pane of a double-glazed window in my house is broken, and I'm curious to know why. Picture below.
I've done some Googling to investigate, and as I it understand the possibilities are:
Impact
This is a second floor window so it would have to be a projectile. My research suggests that this would appear as a series of points originating from a central point-of-impact. I don't see the typical spiders-web pattern, so I don't think this was an act of vandalism.
Heat induced
At the time of the breakage, it was 70F in my house and 39F outside. I don't think this is a sufficient gradient to cause a spontaneous breakage.
Mechanical stress
I'm less sure about this – I can't find consistent information on how this looks.
Edge failures
I don't think the breakage appears to emanate from the edge, so I can rule this out.
Summary
All in all, I'm at a bit of a loss, and was hoping some expert here might be able to help me figure out why my window broke.
Best Answer
That pattern indicates that a blunt object hit it, something relatively soft and larger. A rock or other hard and small object would leave a clear indicator like the picture below, with a central point and circular lines. What larger and blunt object would hit a second level window? Probably a bird. I think that this is a bird strike in the middle of the glass
As an interesting side note, here's an eagle that flow through someone's window last month