The urban heat island effect, whereby the high concentration of heat-retaining concrete and bitumen causes metropolitan centers to be significantly warmer than the rural areas surrounding them, is a common problem around the world. The phenomenon is particularly prevalent in Tokyo, Japan, but among the sea of towering structures stands one beacon of hope. The BioSkin that coats the NBF Osaki Building integrates evaporative cooling to keep its surface temperature down and could inspire new solutions to rising city temperatures across the globe.
The 25-story NBF Osaki Building was completed in March, 2011 and is the first structure to use the BioSkin system. The urban facade is inspired by traditional Japanese air-cooling systems, such as the water-spraying Uchimizu and bamboo blinds known as Sudare. Using these methods as a foundation, researchers at the Nikken Sekkei architecture firm conceived BioSkin with the seemingly counter intuitive aim of improving the local environment through building large-scale architecture.
Rainwater is collected on the roof of the building and drained to a subsurface storage tank to be filtered and sterilized. It is then pumped through a network of special porous ceramic pipes which act as a sprinkler system. As the water evaporates, it reduces the surface temperature of the pipes and the air that surrounds them, with excess water fed to the soil below. Solar panels are also fixed to the south side of the building, acting as shades and helping to reduce overall energy costs.
Nikken Sekkei says that according to its simulations, the BioSkin can lower the surface temperature of the building by as much as a total of 12°C (22°F) and the surrounding air by 2°C (3.6°F). This ability to affect the micro-climate is what gained the BioSkin recognition from the the Council on Tall Buildings and Urban Habitat (CTBUH) which bestowed its Innovation Award on the building earlier this month.
"The potential implications of this are substantial," the CTBUH says. "If a large number of buildings in a city used such a system, ambient air temperature could be reduced to the point that cooling loads for many buildings, even those without the system installed, could be reduced."