John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
A Japanese construction company turns demolition into energy using something it calls a "big hat."
Leave it to Japan to turn one of the dirtiest and noisiest processes of the urban lifecycle – the demolition of highrises – into a neat, quiet and almost cute affair.
As much fun as it sounds, demolition companies don't tackle most jobs with a heavy swinging ball. Taking down a largish building requires extensive crane work, temporary scaffolding and a fleet of heavy machines grinding around on the rooftop. But Japanese construction company Taisei, which is behind the world's tallest concept skyscraper, is pioneering a type of building butchery that seals all these messy elements into an adorable "big hat."
"It's kind of like having a disassembly factory on top of the building and putting a big hat there, and then the building shrinks," says one Taisei engineer, according to this report in the Japan Times. Basically, construction workers build a hermetic structure covering the top floors of a tower that is supported by powerful jacks. Inside the structure are the heavy machines and demolition crews, who take apart the walls and cut the floors into concrete slabs that they lower to the ground via interior cranes. When they finish removing one floor, the jacks move the "big hat" to the next one down, creating the impression for outside observers that a huge, disembodied mouth is consuming the tower from the top down.
Aside from looking cool, the so-called "Taisei Ecological Reproduction" system has several unique advantages. It's never raining inside the "big hat," so crews can work through the worst weather. The emission of dust into surrounding neighborhood is cut by 90 percent, according to Taisei, and noise pollution is greatly muffled. Also, in a process much like regenerative braking, the cranes use the weight of their loads to create electricity, which in turn powers lights and machinery on the construction site.
Taisei is demoing its concrete-disappearing headgear right now at the Grand Prince Hotel Akasaka in Tokyo, which the company asserts is one of about 800 buildings in Japan taller than 100 meters that could benefit from the "big hat" treatment. Take a look at the process in time lapse above; starting at 2:20 in the below video, find a Japanese-language view from inside the disassembly factory. (H/t Spoon & Tamago.)