News Home & Design One Building, One City: World's Tallest Prefab, Sky City, Is Breaking Ground in June By Lloyd Alter Design Editor University of Toronto Lloyd Alter is Design Editor for Treehugger and teaches Sustainable Design at Ryerson University in Toronto. our editorial process Facebook Facebook Twitter Twitter Lloyd Alter Updated February 18, 2021 Screen capture. Broad Sustainable Construction Share Twitter Pinterest Email News Environment Business & Policy Science Animals Home & Design Current Events Treehugger Voices Broad Sustainable Construction informs us that a long and arduous approval process has been completed, and that they are starting excavation and construction on Sky CIty in June, 2013. Why build the world's tallest building in the middle of a field in Changsha, China? Why build it at all? The answer, according to BSC, is that it is the most sustainable way to accommodate a growing population. This is not a trophy like the Burj Khalifa, a thin high tech spire that isn't even connected to a sewer system. They call it a "pragmatic" building, designed for efficiency, affordability, replicability. They also make a strong case for it being sustainable. BSC writes: The world population is increasing at 1.8% year by year. In the near future, land, energy, climate may breach the critical point. Broad Sustainable Building/Screen capture The Sky City concept significantly reduces the per capita use of land, and the CO2 emissions generated getting around. They call it "a way of development for higher life quality and lower impact on the environment" They see this as the future of Chinese city building: "Urbanization can not be materialized at the cost of land and environmental pollution." By going up, hundreds of acres of land are saved from being turned into roads and parking lots. By using elevators instead of cars to get to schools, businesses and recreational facilities, thousands of cars are taken off the roads and thousands of hours of commuting time are saved. It makes sense; vertical distances between people are a whole lot shorter than the horizontal, and elevators are about the most energy efficient moving devices made. A resident of Sky City is using 1/100th the average land per person. © Broad Sustainable Construction If you would rather walk rather than wait for one of 92 elevators, there is six mile long ramp running from the first to the 170th floor. Beside the ramp are 56 different 30 foot high courtyards used for basketball, tennis, swimming, theatres, and 930,000 square feet of interior vertical organic farms. © Broad Sustainable Construction They have built a full-scale mockup of the ramp construction. The numbers continue to stagger. In one building, there will be accommodation for 4450 families in apartments ranging from 645 SF to 5,000 SF, 250 hotel rooms, 100,000 SF of school, hospital and office space, totalling over eleven million square feet. The building footprint is only 10% of the site; the rest is open parkland. Broad Sustainable Construction/Screen capture BSC claims that their buildings are five times more energy efficient than conventional ones, using 8 inch thick insulated walls and triple glazing. There is exterior shading on the windows that cuts cooling requirements by 30% and what cooling or heating is needed comes from a co-generation plant using waste heat from power generation. They don't do the math about how much more efficient living this way is compared to low rise construction, nor do they calculate the Transportation Energy Intensity, the total energy saved by the fact that it is, as they say, a vertical city. © Broad Sustainable Construction There's more: The building is designed to be earthquake resistant to Magnitude 9, and to a 3 hour fire resistance rating, provided by ceramics installed around the structure. 16,000 part time and 3,000 full time workers will prefabricate the building for four months and assemble on site in three months. The Broad system is based on prefabricated floor panels that ship with everything need to go 3D packed along with it, so they are not shipping a lot of air. It all just bolts together. BSC claims that by building this way, they eliminate construction waste, lost time managing trades, keep tight cost control and can build at a cost 50% to 60% less than conventional construction. The design is based on the "bundled tube" structure, first demonstrated in the Sears (now Willis) tower and also used in the Burj Khalifa. BSC notes that "In the past, Super Tall Buildings were form-obsessed, whereas Sky City is a firm pyramidal structure."- they are obsessed with engineering, not style. In a previous post, commenters suggested that this was too big an engineering challenge, but "Over a hundred tests of physical strength & fire resistance were performed, and wind tunnel tests were conducted by three research institutions.... [The design] completed over 10 sessions of government assembled expert group reviews." © Broad Sustainable Construction This is going to be a controversial vision of sustainability; Putting 30,000 people in a single building is a hard sell. It is not the bucolic version of green living that most people think of. It certainly is a lot higher than what I have called the Goldilocks Density. But it is the logical extension of the Edward Glaeser / David Owen thesis that the way to go green is to go up, reducing the amount of land used per person and the distances people travel. Lisa Rochon wrote about the Aqua Tower In Chicago: [Architect Jeanne Gang] notes that Aqua puts about 750 households on a third of an acre, allowing people to walk from their home to their jobs and to culture and recreation. “The most important thing we can do for the environment is live in compact cities with mass transit,” argues Gang, “that reduce the reliance on the car and other resources.” Broad Sustainable Construction/Screen capture This building puts 4,450 households on two acres and it is actually designed with energy conservation in mind. By going huge they are getting tremendous manufacturing efficiencies; by going vertical they get the kind of repetition that makes it affordable. By going half a mile high and 220 stories they are going to get noticed. It is a vision of sustainability that people in a crowded world are going to have to get used to.