Near the end of the movie, Sam, Brian, and DJ, after finding the medicine on the ship outside the library and fending off the wolves, begin to run back to the library. A shot of the Empire State building that the rapidly descending temperature is able to break through glass. However, the "cold" doesn't reach the room in the library until it seeps on the floor of the library and finds its way into the room. Shouldn't it have just cracked open the window and killed them all? Why would the cold break windows of other buildings but not the library?