It took Dubai more than five years to build the 828-meter Burj Khalifa, the world’s tallest building (for the moment, anyway).

But Chinese architects and engineers reckon they need a mere 90 days to leave the Emiratis in the dust.

At least, that's what they've claimed.

Broad Sustainable Building (BSB), a construction company based in Hunan, is planning to erect an 838-meter building called Sky City (天空城市) later this year in Changsha, the provincial capital of Hunan Province.

Projected cost for the building is RMB 4 billion (US$628 million).

Once completed, the 220-story structure will surpass Burj Khalifa to become the tallest structure in the world.

The building will also outshine China’s current skyscraper poster boy: the 632-meter Shanghai Tower (上海中心).

BSB inked an agreement last week with authorities from Wangcheng district in Changsha, where the building will stand, but the project is still pending approval from central government, reported Xinhua News Agency (in simplified Chinese only).

Innovative techniques

In an interview with Xinhua, BSB chief executive officer Zhang Yue (张跃) said the company plans to break ground on Sky City in November 2012, and that the tower will be completed in January 2013.

The company is confident the government will green-light the project.

BSB is renowned for its eye-opening construction efficiency. Its portfolio includes assembling a 15-story building in six days in June 2010, and erecting a 30-story hotel in 360 hours in December 2011.

More on CNNGo: World's tallest tower, Tokyo Skytree, opens

The key to achieving such stunning speed is an innovative construction technique developed by BSB.

Most of the company’s buildings are pieced together with prefabricated components from its factory. In this case, 95 percent of Sky City will be completed before breaking ground.

Energy and cost saving

According to BSB, the new mega-building was designed by an architect from Dubai.

Its 220 stories will provide a total of 1 million square meters of usable space, linked by 104 elevators.

Zhang said Sky City is expected to consume a fifth of the energy required by a conventional building due to BSB’s unique construction methods, such as quadruple glazing and 15-centimeter-thick exterior walls for thermal insulation.

The company's construction methods also seem to save money.

According to Chinese newspaper 21 Century Business Herald, the total investment in Sky City is RMB 4 billion (US$628 million), compared with US$1.5 billion on Burj Khalifa and US$2.2 billion on Shanghai Tower.

More on CNNGo: 20 of the world's most iconic skyscrapers

Hunan-based BSB is yet to release more details of the building, such as its function, and how long it takes to manufacture all its components.

BSB has also declined requests for images of the building design, but China Radio International released a possible image of the model for Sky City.

Not a landmark, a lifestyle

At 632 meters, Shanghai Tower will rank as the tallest structure in China by the time it's completed in 2014. Ground was broken on the 121-story tower in Lujiazui in 2008.

It’s also expected to house the world’s highest hotel, J Hotel, once the building is completed.

“Since the project is still pending, we have no comment on [Sky City] -- but it’s very hard to believe that [BSB] will be able to build an 800-plus-meter skyscraper in [such a short period of time],” said Shen, a public relations officer for Gensler, the company that designed Shanghai Tower.

More on CNNGo: Best skyscrapers in Shanghai

BSB explained to Xinhua that its goal of building Sky City is not to erect a new landmark in China, but to develop and put into use a “medium-cost, super-saving utility building and to promote a futuristic urban lifestyle.”