Historically, height and attractive aesthetics have generally been the features that have conferred landmark status onto some of the world’s most iconic skyscrapers.

This is evident in New York’s Empire State Building, Kuala Lumpur’s Petronas Twin Towers  and the sail-inspired Burj al Arab in Dubai, all of which remain prominent fixtures in their cities’ skylines.

Today, the dream of breaking the one kilometre mark is within reach following this week’s announcement that construction will begin in late April on what is proposed to be the world’s tallest skyscraper – the 1,000 metre tall Kingdom Tower in Saudi Arabia.

1,000 metre Kingdom Tower

Construction is set to begin in April on the 1,000 metre Kingdom Tower

The one-kilometre mark is but a starting point for some ambitious plans, however.

Daniel Safarik, editor of the Council on Tall Buildings and Urban Habitat (CTBUH) revealed that the highest and most “audacious” project on record remains the 4,000-metre X-Seed 4000 in Tokyo, which was proposed back in 1995.

The project, designed by Peter Neville of Taisei Corp, would see the mixed-use skyscraper function as an entire city with the ability to house up to 1,000,000 inhabitants.  That vision was inspired by Mount Fuji and the building would have an immense base.

X Seed Skyscraper in Japan

Tallest proposed skyscraper: the 4,000-metre X Seed Skyscraper in Japan

Nakheel Tower, meanwhile, was proposed 10 years ago and was set to rise 1,400 metres. Work began on the project but was put on hold in December 2009 due to the Global Financial Crisis.

As cities prepare for mass urbanisation, however, height will no longer be the primary pinnacle of a landmark tall building. After all, what is height without purpose?

Performance Buildings

Safarik believes that while skyscraper developers are still aiming to deliver height, there is a growing trend toward delivering more.

“Over the next three years, the number of tall buildings expected to complete is 1,118 buildings, at a range of 60 to 660 metres,” he said. “But we’re also seeing performance building becoming an increasingly important attribute of tall buildings including environmental, social and economic performance in that description.”

“Then you have buildings that are really shooting for a combination of both, like the upcoming 632-metre Shanghai Tower, which is to finish late this year or early next.”

Shanghai Tower

Shanghai Tower: A vertical community and a performance building

The Shanghai Tower will be a mixed use building combining a hotel and office to create a “vertical community.” Designed by Gensler, the building will focus on public space and will also feature retail, cultural spaces, conference facilities and hospitality amenities.

While its height would make it the second-tallest building in the world, Shanghai Tower will also be awarded LEED Gold status due largely to the building’s double skin.

Bosco Verticale in Milan, Italy

Green skyscraper, Bosco Verticale in Milan, Italy

“I think both the height ceiling and the sustainability ceilings will continue to be broken,” Safarik said. “I do think there will be an increasing cachet to buildings that are both super tall and super green. But frankly, to date we have found it more economically lucrative to push heights than to move ‘green-scrapers’ forward at a similar pace. Many of the ‘environmental’ skyscrapers to date have disappointed or fallen short of their goal.”

Many tall buildings’ environmental design features aim only to “do less bad” as Gunter Pauli, entrepreneur, activist and author of The Blue Economy told Green Cities participants last year.

Melbourne's RMIT Design Hub Building

Double skin facade at Melbourne’s RMIT Design Hub

“It’s time to do more good. Stealing less is stealing. Polluting less is polluting. Don’t fool ourselves, zero per cent is the minimum,” Pauli said.

Iconic Buildings

Joseph di Pasquale from AM Progetti S.r.l in Milan, the Italian architect behind Guangzhou Circle, the world’s tallest circular skyscraper, agrees with Safarik on the move to performance building along with the aim for buildings to be recognised as icons.

Guangzhou Circle

Guangzhou Circle, an urban ideogram for skyscrapers

“The traditional race for the tallest building in the world will end sooner or later directed by the limits of the materials strength and mostly because of financial reasons,” he said. “Then the competition will be moved from the height to the iconic value.”

This methodology directed his design of Guangzhou Circle, a building with a structural design that reflects the ancient Chinese culture of its city. While it might only rank as the 87th tallest in the city, it stands out as what di Pasquale would like to see recognised as an “urban logo,” similar to ideograms that are used in Chinese writing instead of the alphabet.

“I think this building could be a way for the future of landmark buildings,” explains Di Pasquale. “Not precisely the circular shape but the central and iconic composition of the shape,” he said.

Height Will Persist

The Illinois

The Illinois, a 1610-metre tall building proposed

No matter how aesthetically pleasing or green a building is, height is here to stay. The question is, how high can buildings go?

“[T]he consensus seems to be that the mile-high (1610 metre) skyscraper, envisioned at least as far back as Frank Lloyd Wright’s time is possible,” Safarik said. “The question really becomes, who can afford to build and find tenants for a building that would have to be so massive at the base as to forbid light from getting into its core – who would want to be in that space? There has so far been no economic justification.”

Like DiPasquale, Safarik agrees that cost is crucial, and only buildings with extremely wealthy backers who can withstand the time it would take to fill the building with occupants will be viable.

However, for the ambitious, Safarik reveals some technologies that will aid developers in breaking the height barrier.

Carbon Fibre Skyscrapers

Carbon Fibre

Carbon Fibre hosting rope for elevators in skyscrapers

“There are two applications of carbon-fibre (similar to the material now being used in some aircraft like Boeing 787 Dreamliner) that are promising. People have talked about using carbon-fibre to make lighter structures than we can make with the concrete and steel we use now,” Safarik said.

While not tested, carbon fibres could provide for the skinnier, taller and thinner buildings. Carbon fibre cables are already being used in some elevators.

“At a fraction of the weight and the coiling depth of a steel rope, carbon-fibre can allow lifts to rise up to 1,000 metres in a single run,” Safarik said. “Currently the limit is around 500 metres, so people traveling to the top of 500-metre-plus buildings have to transfer at some point. All other factors being equal, theoretically if people now tolerate a two-cab ride to the top of a 500-plus (metre) building, they will tolerate a two-cab ride to the top of a 1000 to 2000-metre building.”

Crackdown on Vanity Height

Late last year the CTBUH coined the term Vanity Height – the distance between a skyscraper’s highest occupiable floor and its architectural top.

A report investing this growing trend sparked global media coverage when it was revealed that the some of the world’s tallest skyscrapers had a great deal of unused space.

The 321-metre Burj Al Arab had the highest non-occupiable-to-occupiable height ratio of 39 per cent, equating to a vanity height of 124 metres. The world’s tallest building, the 828-metre Burj Khalifa featured a non-occupiable-to-occupiable height ratio of 29 per cent, or 244 metres of vanity height.

The CTBUH is now making it their mission to further investigate buildings and recognise that the impact of a tall building is far wider than just the building itself.

“We are launching an Urban Habitat award in our next awards program, which respects the fact that buildings need to contribute to their overall environments, not just be tall,” Safarik said.

The Urban Habitat award will join the current ten awards issues annually for tall buildings across the globe with entries closing next month.