we had a metal roof instaled 7 years ago. every fall we get up there and tighten the screws. they have backed out 1/4 to a half inch !! we do this at least once a year. we have a temp spread here of 25 degrees f. ( sometimes colder) and up to 110 in the summer.. the roof is dark green.. we still get an occasional leak it drives us wild.. any ideas ?? thanks