I'm talking about the backside of the bands. That's what resident see, but window cleaners can't. And the bands are white so dirt will be more visible.
OK that I could see will very likely be an issue, you're right, sorry I misunderstood.
March 30
As you can see in Drum's photo here, the bands are actually held several inches away from the windows, allowing ample room for cleaners to wipe-down the back sides of them.
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