How do you even get up there without knockouts? There's like 3 different guards that see the scaffolding you climb on.
Timing! And only one of the guards is actually the issue( the one that patrols from the truck to the gate). The one right below the scaffolding only sees you if you skip the first window. If you wait for the window guard to exit, you can enter the window and the guy below will not be suspicious.