When you think of a prefab, what comes to mind? A house in a neighborhood full of identical houses? How about a building in China with 57 floors and 800 apartments? That's exactly what Broad Sustainable Buildings has constructed in Changsha. Billed as "the world's tallest prefab," the building also has 19 atria stacked on top of each other for social areas and makes use of several air purifying construction techniques.

"As usual for Broad's buildings, they are really efficient, with 8" of insulation and quadruple-glazed windows and the best air quality in China, with 3 stage air purification, particulates reduced by 99.9%, 7 air changes per hour and 100% fresh air that's run through heat recovery ventilators. It's got combined heating, cooling and power, (Broad's main business is air conditioning) making the building 80% more efficient than conventional buildings. Broad claims that this one building saved 15,000 trucks full of concrete."

Check out more photos of the building, and speculation as to why you won't see them everywhere despite being easier to manufacture, over on Treehugger.