I was talking to a man last night, and he told me how he had stood atop a 12-ft. ladder to repair a light. This led to a discussion of ladders in general, as well as other ways to reach high places.
The first issue that arises is that, once you pass the 12 ft. mark, ladders become two-sided 'mechanics" ladders. The have a larger footprint, weigh twice as much, cost twice as much, and become incredibly difficult to handle.
I recalled that Little Giant has a "skyscraper" telescoping ladder that will get you to a 21 ft. ladder height (working height around 24 ft.) This ladder, alas, is only made in aluminum.
How else to get 'up there?' Scaffolding? Scissor lift? Boom lift? All can work, but .... none of them have the insulating properties of fiberglass.
So, we have to ask: Why is a 20 ft. aluminum ladder forbidden, but a 20 ft. steel scaffold if OK?
