Well we now have our answer on why the windows haven't been washed yet on 1 WTC:.
A majority of the windows at One World Trade Center haven’t been washed since 2015, because the system used to suspend the washers isn’t safe, a representative for the Durst Organization TRData LogoTINY told The Real Deal. Typically, a boom at the top of the building lowers a window-washing rig that moves horizontally as the boom moves along a track on the roof. But in early 2016, Durst noticed that welding in the track — where pieces of metal are joined together — was riddled with cracks. The track, built in 2013, also has undersized bolts and suffers from other design flaws, said Jordan Barowitz, a spokesperson for Durst.
“The window washing units at One World Trade Center have failed and are being replaced,” Barowitz said in a statement. The developer is in the process of finding a company that will build a new system, which is expected to cost millions of dollars (though a total price has yet to be determined).