Sensor and sensibility

A building facade that acts like a reactive skin and responds to the changing environment around it will significantly reduce energy consumption, according to its UK developer.

Engineers at Arup Associates have designed a facade that reacts to changes in levels of sunlight and wind at local points, lowering blinds where the sun is shining directly on an area of the building, but leaving them up to allow in maximum light where it is not.

The reactive skin will be unveiled on Plantation Place, an Arup-designed office building in central London due to be completed in 2004. The system will reduce energy consumption, allowing people to turn off lights and become less reliant on air-conditioning, said Mike Beaven, practice principal at Arup Associates.

‘Air-conditioning systems are inefficient because if the sun is striking one part of the building making it hot the other half remains cool.’

The reactive skin consists of around 150 light and motion sensors, each working autonomously rather than through a central computer. ‘We wanted to see if we could benefit from the skin responding at a microscopic level rather than having a single brain. Normally a computer controls everything, but we wanted to spread that out so that the facade itself is self-controlled and self-moderating,’ said Beaven.

City landscapes are constantly changing, with buildings being demolished and new developments erected. So the autonomous nature of the skin allows it to react to new areas of sunlight and shade as they appear. Using a large number of sensors rather than just one device also means the consequences of any failure are significantly reduced, said Beaven.

Office buildings, particularly those with glass facades, trap too much heat inside, and blinds inside windows offer no protection as sunlight gets through the window as far as the blind, but cannot get back out again.

The sensor-controlled blinds on Plantation Place will be hung on the outside of the facade, behind an outer shield of slatted glass that will allow air to flow in and out, taking the heat away from the building. The blinds cannot be used in strong winds, so movement sensors will monitor air velocity at different points on the facade and fold them back if necessary.

The industry is also looking into the use of coloured windows based on metal deposition on glass, where the wavelength can be programmed to change either to reflect light or allow it through at different times of the day. But the Holy Grail will be to develop a truly reactive coloured window system, where the wavelength changes actively in response to conditions, said Beaven.

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