Developed by Japanese architecture firm Nikken Sekkei, the Sony City Osaki Building in Tokyo is the first building in the world to use a natural ‘BioSkin’ cooling concept, which draws heat away from the building as water evaporates around it, thus causing the surrounding air to cool.

The BioSkin concept was inspired by traditional Japanese techniques to cool the air such as bamboo shading screens, called Sudare, and a water spraying technique called Uchimizu. The system comprises specialized ceramic louvres which funnel rainwater through the system. In effect, the system acts as an enormous sprinkler for cooling the building environment.

The BioSkin tubes are made from extruded aluminium cores, with a highly water-retentive terracotta shell attached to the core via an elastic adhesive. When rainwater collects on the rooftop, it drains to a subsurface storage tank where the water is filtered and sterilized. The water is then pumped up and circulated through the pipes, which are incorporated into balcony railing and horizontal screens.

The rainwater penetrates outward through the ceramic cores, evaporating from the pipe’s surface and cooling the air. Excess water is drained down to the ground surrounding the building, helping to recharge the ground water cycle and reduce the load on drainage systems.

Based on tests and experiments, it has been shown that as the water evaporates, the temperature of the ceramic pipes and the surrounding air drops by an estimated 2 degrees Celcius.

On the south facade of the building, protruding solar panels are installed on the facade. Like the BioSkin system, the solar panels double as a shading device, producing energy while helping to keep the interior of the building cool.

According to the architects, ‘The building was conceived as a massive cooling device that performs in much the same way as a natural forest.’