Prefab Sky City in China, world’s tallest building, to be up in 80 days

  • At 838 m, it surpasses Dubai’s 828-m Burj Khalifa as tallest building
  • BROAD looking for franchisees for its BSB building system 

By Stephen Ng


The modernist Chinese penchant for size and efficiency is taking prefabricated building construction to the clouds – literally. The most ambitious recent project is to build the world’s tallest building in 80 days. Upon completion, it would be 838 m tall, surpassing the 828-m Burj Khalifa in Dubai.


The 220-storey Sky City in Hunan province has three major milestones: Obtain land (June 2012), start on-site construction (November 2012) and complete project (January 2013). 


This is a massive challenge, like that in Jules Verne’s Around the World in Eighty Days where an adventurer and his valet attempted to circumnavigate the world on a 20,000 pound wager (over 1.3 million pounds or US$20.1 million today). 


In the mindset of the typical bureaucrat, such a project would take a minimum two years to approve and at least another two to complete. This feat by China’s BROAD Group would shatter this belief and practice. The group is both the technology owner and the developer of this mammoth tower.


The Sky City by the Xiangjiang River in Changsha, the capital of Hunan, will be a vertical self-sustaining township housing over 70,000 people. Says Juliet Jiang, senior vice-president of BROAD Group China: “It will be a low-carbon city. Using very little land for the construction of an entire community, we have designed it to be a vertical city. In fact, we will have farms and plant trees around the project. 


Juliet Jiang (photo credit: GPA Photo)

“Because the entire city will be served by 104 lifts, people living in it would not have to drive to work. There will be the usual shops, offices, supermarkets, hospitals, clinics and so on. It is an entire community living within the same building. Instead of spreading over a large piece of land, the city is built skyward.” And, despite its size, it can withstand an earthquake of magnitude 9 on the Richter scale


Jiang gave a talk organised by the Green Building Index Accreditation Panel in Kuala Lumpur recently. 


To construct the building, the engineers will have to work within the constraints that they have. They will have to work on 30 floors at a time. Once completed, the earlier floors will be used as a platform for the next 30 floors. This is partly due to the limitation of conventional cranes. 


In fact, the BROAD Group has recently completed two projects that have been the talk of the construction industry: 

T30 Hotel: On-site construction for this 30-storey tower, along with a helicopter pad, took just 15 days. Prefabrication of the materials, done during the laying of the foundation, was about 40 days. It has earned BROAD Group the title of the fastest builder on the planet. A video clip on it, “30-storey building built in 15 days”, went viral and was watched by millions within two weeks after it went online on YouTube.

New Ark Hotel: This 15-storey project in the south-central Chinese city of Changsha was built in one week. 


The building of the hotels is governed by precision, from materials and their sizes to timing and logistics. For example, the modules, each weighing around 18 metric tonnes and measuring 15.6 m (length) by 3.9 m (width), are designed to enable the trailer to pass through toll gates. 


The moment the trailer reaches the site, the modules are raised to the level where they are to be installed. No time is wasted in loading and unloading. Everything is planned to be delivered “just-in-time.”


Construction is intensive and carried out around the clock with 250 workers on each shift. “Each worker can install 3 sq m per day,” says Jiang. On-site construction takes up only 7% of the project, because 93% of the building is factory-made. Each 3.9 m by 15.6 m “main board” includes flooring and ceiling, embedded shafts for ventilation, water supply and drainage, as well as electrical wiring for lighting.


(photo credit: BROAD Group)

The cost of building the T30 tower is just below US$1,000 per sq m, as the design uses only 68 kg of steel structure per sq m, compared with conventional buildings at 75 kg per sq m reinforced concrete and 140 kg per sq m steel. “In China, our BROAD Sustainable Buildings (BSBs) give 10% to 30% in savings compared to the conventional building,” Jiang says. 


What is also interesting is that T30, although originally designed and built as a 3-star hotel, can be easily converted into a suite apartment to be sold off as individual units. “We have made our design very flexible,” says Jiang. “You can remove the wall to make two rooms into one bigger living room.” 


The T30 Hotel, built on Dongting Lake in Hunan province, is indeed BROAD’s most amazing feat thus far. It has 330 hotel rooms with a total floor space of 17,338 sq m (or 578 sq m on each floor). 


According to Jiang, the T30 tower is five times more energy efficient than most other conventional hotel buildings. This is based on heating, ventilation and air-conditioning (HVAC) energy consumption figures. The HVAC of conventional buildings around the world, in terms of heating oil used, equals 35 to 70 litres per sq m per annum (L/m2a). In the case of BSBs it is only 7–12 L/m2a. 


“Besides that,” adds Jiang, “in cold countries, conventionally, the thermal insulation is 10 cm thick and uses double-paned windows, but in the case of T30, we use 15 cm thermal insulation and four-paned windows.”


BROAD’s own heat recovery fresh air system helps to recover 70% to 90% of energy and ensures a high level of indoor air quality. It also helps to recover heat between outdoor fresh air and indoor exhaust air. 


With BROAD’s fresh air machine, which has a three-stage filtration, the air quality in the hotel is at least 20 times purer than outdoor air. To monitor the indoor air quality, an expensive detector is installed in every room to check the indoor particulate matter, formaldehyde and CO2 levels, and compare it to the outdoor particulate matter level. 


“This is because the indoor air quality is very important for every guest of the hotel,” Jiang explains. “WHO has certified that 68% of human diseases are related to indoor air pollution.”


In May 2011, BROAD’s founder and chairman Zhang Yue was awarded the Champion of the Earth Award (Entrepreneurial Vision Category) by the United Nations Environment Programme for the company’s commitment to climate change. It was one of ten companies to be recognised by the BusinessWeek Greener China Business Awards in 2009, and was also named one of the “20 Most Admired Companies in China” in 2001, 2002, 2004 and 2005 by China’s Economic Observer and Beijing University.


In order to spread its wings, Zhang has decided that the group will look for franchisees around the world. Due to the vastness of China, logistics for any of the modules beyond 500 km would immediately negate the benefits of any carbon reduction initiative. “This is why we have to franchise our system,” Jiang explains. 


For example, the Russians have approached the BROAD Group to construct a new hotel for the coming Sochi Winter Olympics. “However, it is not economical to transport the building modules from China to Russia,” she says. “After 500 km of transportation, for each 100 km, the cost would go up by another US$3 to US$5 for every sq m.”


In China, BROAD has six franchisees in different cities. “The franchisee fee is US$34 million upfront for a country with a population of ten million,” said Jiang. “For countries above 50 million in population, it is US$50 milion for the franchising fees. There is a 20% discount for the early bird among international franchisees.”


For every project, there is a US$20 per sq m royalty for developing nations, while for developed nations, it is US$50 per sq m. The technology transfer includes the next 70 years on the use of various designs of BSBs. 


Main specifications of Sky City One

Building area: 1,610,000 sq m (plot ratio: 50)

Land area: 32,400 sq m (180×180)

Construction material: Approx 400 kg/sq m

Energy consumption: 90 kWh/sq m/annum

Fabrication term: Four months for fabrication, two months for installation

Occupancy capacity: Rated 70,000 people, maximum 100,000 people