Study: Skyscrapers Topped by Wasted Space

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The world's tallest building are capped by anywhere from 20 to 40 percent of wasted space, according to a new study by the Council on Tall Buildings and Urban Habitat.

The study focused on what the CTBUH calls "vanity height," defined as "the distance between a skyscraper's highest occupiable floor and its architectural top." In many of the world's tallest skyscrapers, the space is filled by spires and architectural elements that "do not enclose usable space," based on the Council's standards.

For example, 244 meters of the 828-meter Burj Khalifa, the world's tallest building, is rated as unoccupiable, 29 percent of the height. Burj Al Arab, the sail-shaped hotel off the coast of Dubai, has the highest ratio of vanity space of any supertall, with 124 of its 321 meters (39 percent) devoted to non-occupiable space.

The Council labels the Ukraina Hotel in Moscow as the "vainest" in the world - 42 percent of the 206-meter tower is non-occupiable.

But the United Arab Emirates steps as the country with the most wasted-space skycrapers, with an average of 19 percent of the towers dedicated to non-occupiable space.

But Dubai is not alone in tacking on height to its skyscrapers. Sixty-one percent of the world's 71 supertall towers - with supertall defined as 300 meters or taller - would no longer be classified as supertall if the vanity height was subtracted, according to the Council's data.

The CTBUH is a non-profit association for builders and designers of tall buildings. Although it has no official role, it has become the arbiter of tall building heights and maintains an extensive database on tall buildings around the world.