Why did the John Hancock Tower fail?

Why did the John Hancock Tower fail?

The opening of building was delayed from 1971 to 1976, and the cost went from $75 million to $175 million, according to The Globe. The window issue persisted for four years, according to The Globe. It was discovered that the cause was in the design of the window, so all 10,334 panes of glass had to be replaced. Jul 15, 2015