Since ancient times, people have built structures that reach to the heavens – from the steep spiers of medieval towers to the great domes of ancient cathedrals and mosques. Today the mission is to build the tallest skyscrapers in the world, like the Burj Khalifa in Dubai. Towering above the rest, its decorative spire represents 29% of its total height – 4,000 tons of structural steel for aesthetics alone.
Burj Khalifa is not alone in this regard. “Vanity height” – the extra height from the highest occupied floor of a skyscraper to its architectural top – shapes city skylines around the world.
In a world where environmental concerns are paramount, is such architectural vanity justifiable?
Our research shows that the search for the “height of vanity” makes this issue urgent. Even a modest tower increases carbon emissions from producing materials for a skyscraper’s structure by about 15%.
Building tall isn’t just about architecture; It’s a big deal. Being ranked among the tallest buildings in the world can transform an ordinary skyscraper into a globally recognized icon. This creates an incentive to add vanity height.
Our proposed solution is to rethink the global standard for classifying the world’s tallest buildings.
Adapted from Helal et al. (2024), using data from the CTBUH Skyscraper Center, CC BY
A question of measurement
How we measure the height of skyscrapers is at the heart of this question. The Council on Tall Buildings and Urban Habitat (CTBUH) is the highest authority on skyscraper heights. It confers the coveted title of “tallest building in the world”.
Historically, there hasn’t been much debate about the height of skyscrapers, as early buildings typically had flat roofs. The first significant issue arose in 1929, when New York’s Chrysler Building installed a last-minute tower, securing the self-proclaimed title of “tallest building in the world” above the Manhattan Bank.
The Council on Tall Buildings and Urban Habitat, founded in 1969, established criteria in the early 1970s that included decorative towers. This formalized a practice that would be continually controversial.
A landmark moment in the council’s history was the 1998 clash between the Petronas Towers in Kuala Lumpur and the Sears Tower in Chicago, now known as the Willis Tower. Imagine these two giants side by side: the spiky 88-story Petronas Towers and the flat-topped 108-story Sears Tower. But the municipality uses “height to the architectural top”, which includes decorative spiers. As a result, Petronas Towers was declared the tallest building in the world, surpassing Sears Tower in the title race.
Adapted from Helal et al. (2024), using data from the CTBUH Skyscraper Center, CC BY
Back in Chicago, this was not a popular verdict. Imagine people on the 108th floor of the Sears Tower looking down on the celebrations on the 88th floor of the Petronas Towers, perplexed by how those extra meters of spire made a difference. The decision even reached popular culture, with Jay Leno joking on The Tonight Show:
All the council does is, once every ten years, look up at the sky and say, ‘Yes, that’s the highest one!’
Even if extra height doesn’t guarantee a spot in the world’s 100 tallest buildings, height still matters. Skyscrapers gain valuable cachet as the tallest in their city, region, or country, or by earning use-specific accolades such as “the tallest restaurant in the world” or “the tallest religious space in the world.”
The Hidden Cost of Vanity Height
Sixty years ago, renowned Bangladeshi-American architect and engineer Fazlur Rahman Khan demonstrated the exponential impact of a building’s height on the amount of material needed to construct it. In fact, doubling the height of a building could triple the structural materials needed. A stronger structure, using more materials, is needed to withstand greater wind loads and earthquakes in taller buildings.
This means there is a large “embodied carbon premium for height”. This premium corresponds to the additional greenhouse gas emissions resulting from the production of the additional materials needed for a taller skyscraper.
A telling example from our study shows that even a modest spire, representing 16% of a building’s total height, can increase the embodied carbon of a 90-story skyscraper by 14%. By maximizing building height for aesthetic, status or financial reasons, designers are prioritizing these concerns over environmental sustainability.
Adapted from Helal et al. (2024), CC BY
We took an in-depth look at Dubai, a city famous for its imposing skyline. We found that the collective height of its 100 tallest buildings adds up to more than 3.5 kilometers.
We estimate that these decorative elements contributed to at least 300,000 tons of greenhouse gas emissions. This is both the embodied carbon directly in the towers and, much more importantly, the embodied carbon added by reinforcing the buildings to support the extra structural loads.
To put this impact into perspective, 300,000 tonnes of emissions is equivalent to the embodied carbon associated with building around 2,400 average Australian homes. It’s a high price to pay, simply adorning 100 skyscrapers with pointy hats that inflate their height and status in global rankings.
Redefining heights to establish more sustainable standards
The Council on Tall Buildings and Urban Habitat, which champions the motto “Towards Sustainable Vertical Urbanism,” has a crucial opportunity to lead change. What if we revised the way we measure and classify tall buildings to better reflect this commitment to sustainability?
In light of our findings, we call on the council to remove the incentive to rise to vanity. We propose that “height to highest occupied floor” be adopted as the main standard for classifying skyscrapers by height.
Such a change could be controversial. The Burj Khalifa would maintain the title of tallest in the world, but the One World Trade Center, at 155 meters high, for example, would fall nine positions, losing its status as tallest in North America.
However, for every building that falls in the rankings, others will rise. Our research shows that there are more winners than losers among the world’s 100 tallest buildings. Therefore, support for this change may overcome resistance.
Adapted from Helal et al. (2024), using data from the CTBUH Skyscraper Center, CC BY
Cities continue to grow and environmental challenges are becoming more acute. The need to reevaluate our approach to architectural design is becoming increasingly pressing. In particular, features of vanity architecture, such as excessive decorative towers, overwhelm not only our skyline but also our environment.
Ultimately, we will all be better off if we change the way we classify the world’s tallest buildings.
