Vanity height: how much space in skyscrapers is unoccupiable?

In a world of ever-reducing space, a skyscraper is an efficient way to create homes and offices without too large a footprint. It is interesting, then, that so many skyscrapers are full of hot air. In the race for the biggest buildings, architects have fallen back on antennae and pointed spires – with the result that skyscrapers are not so much efficient uses of space, but overblown vanity projects.

Via theguardian.com