Do you want the eaves of the new addition to be higher than your existing eaves? If not, I don't see how the height of the existing eaves factors in. The new addition with a shed roof will give the new room the same ceiling height as the existing room where the sliding glass door is.not sure we have enough height to do it that way the eves are only about
6' 8" above the deck! Oh and this doesn't get much snow it's on the Washington Coast!