Corrected entry: When the rider summons the cold, the window freezes. If window glass were to get that cold that fast it would shatter. The cold does manage to find it's way in and everyone's covered in frost and there are huge icicles in the house. First off, somebody would've woken up if they weren't dead already. Second, icicles need liquid water to grow and they don't grow in extreme cold. Also, even falling icicle's that large would likely injure but not kill someone (the ones that weren't controlled by magic).