Optimisation and design of ducted daylight systems

There is growing interest in the use of ducted daylight systems as a means of increasing the natural lighting of buildings. Such systems are also known as 'daylight guidance', 'tubular rooflight' or 'light-pipe' systems. Four coordinated experimental campaigns have been undertaken since 2004 in order to provide coherent test data for a wide range of light-pipe systems. In total, over 650 hours of systematic monitoring of light-pipe systems and components, mainly under natural daylight conditions, and also with supplementary laboratory measurements have yielded a wealth of data on the performance of the systems. These data have allowed system losses to be quantified according to ambient lighting conditions and have also enabled a generalised design model to be developed to predict system outputs according to ambient conditions. This model now serves as the basis of design for the tested systems.