What about some stone. I think that would look sharp.

Use cinder blocks

How about etched glass, or tinted or frosted plexiglass? It
would need a frame of some sort, I suppose:

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I would use horizontal narrow boards of teak, ipe or redwood (leaving some space between the boards). Lovely house.

are you sure that you need privacy up there? :-)))

Great house and fabulous view! You could also make "walls" and stucco the walls to match the house. I think a good pressure washing may take care of the mold off the walls?

You can use outdoor umbrella drapes , just put some post on the corner ( metal one may be?) and rods ( as shower curtain)