Anything you build on earth is inside the atmosphere. Keeping heat away from greenhouse gasses is the whole point. Objects in space are generally also subject

Anything you build on earth is inside the atmosphere. Keeping heat away from greenhouse gasses is the whole point. Objects in space are generally also subject to less weather, and as such they don't materially degrade. You could make a shield out of opaque film that would tear to shreds at the slightest breeze (see JWST sun shield)