DINGY offices in concrete jungles could soon be filled with natural sunlight. The developers of a new polymer film say that building it into office windows should brighten up the workplace. This would reduce the need for artificial light and significantly cut energy bills, they say.
When the sun is high in the sky, it often causes glare near the window but doesn鈥檛 penetrate deep into the room. So Peter Milner and his colleagues at Redbus Serraglaze, in Knowle near Birmingham, decided to even out the distribution of light by redirecting some of it towards the back of the room.
They made thin, transparent sheets of polymer with a very fine jagged surface. When one sheet is turned over, rotated through 180 degrees and glued on top of another, the two lock together. However, they are designed so that the interlock isn鈥檛 perfect, but leaves tiny horizontal air channels running through the film.
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The team bonded the millimetre-thick film between two panes of glass and installed it in a test room. They then measured how much light reached the back. 鈥淢uch more light is carried into the room at the expense of light falling just inside the window,鈥� says Milner. 鈥淒epending on ambient conditions, we get a 50 per cent to a tenfold improvement.鈥� The film works because light from overhead is reflected upwards towards the ceiling by the air channels. The channels cause total internal inflection of 99 per cent of the light hitting them, says Milner. When the light hits the ceiling, it is scattered more evenly around the room.
Mike Wilson of the Low Energy Architecture Research Unit at the University of North London is impressed: 鈥淭here are a few daylight-redirecting systems available, but they tend either to use prisms, which produce rainbows, or they block your view.鈥� With Serraglaze, the view is less distorted, he says.
