Читать книгу Creating an Eco-Friendly Home & Workplace - Paul Hymers - Страница 16

Light tubes are little more than thin aluminium pipes that are pushed together in short sections to build a tube. The inner surface is highly polished and reflective, having either an anodized finish or a multi-layer polymeric film coating, which allows most of the daylight to bounce down the tube and into your room via a ceiling diffuser. Low technology to say the least, but they are effective. I have seen a 300 mm-diameter example, in bright sunshine, easily light a small internal bathroom. On dull and overcast days, the light level drops off rapidly, but for much of the time a tube of that size can light an area of 10 sq.m to a comfortable level. Some tubes look a bit like an aluminium version of the flexi-hose used for tumble driers and air vents, but although these are easier to install and are much cheaper, they don’t have the reflective qualities necessary to make them worthwhile. When you realize that some reflection of light is knocked back at the roof lens, then again within the tube as it travels down it and finally at the diffuser, you can see that you can lose a good percentage of daylight in the equipment. Hence the shorter the tube and the wider its diameter, the more daylight you will receive. These tubes come in diameters up to 750 mm, but few of us can accommodate such a large duct in our homes. If all you had to run it through was the loft space, it might be possible, but for most lofts, a tube no more than 2 m long would allow a 300 mm-diameter model to be used quite satisfactorily.

Light tubes are assembled from kits, in sections

Assembled light tube