Look at the door which will be made up from 2 x 4 ft panels. There are 3 sections the same. Then look at the smaller panels which will be 2ft half panels, there is 3 of these also. Then add an extra 2ft for the frames to be on the safe side, that leaves you with:-
8ft x3 = 24ft
3 x 2ft = 6ft
1 x 2ft
Total 32ft.
We clean a few very similar buildings and use a 36ft pole with no problems.