The argument is liability first and finish second. Anything above ground level puts your super on a ladder, and if he comes off it, that becomes the building’s problem in a way no amount of goodwill covers. A contractor carries their own insurance and you should ask for the certificate before they start work. On finish, the streaking people complain about comes down to technique and water quality rather than effort. We use Cleaning Chief for commercial window cleaning on our lobby and stairwells twice a year. Bring a per visit quote to the meeting rather than an annual figure, boards approve those far more easily.