Modelling light-pipe performances—a natural daylighting solution

Much research has been conducted looking at the advantages of using natural daylight for illumination of both domestic and commercial buildings. As an alternative to electric lighting, natural daylight, when exploited to its maximum potential, can be beneficial both economically and environmentally. There are many different applications that have been put forward as a way to maximise natural daylight—one of the most simple is the light-pipe. To investigate the effectiveness of light-pipes, a model is proposed that will predict the light levels resulting from a pipe of given dimensions. This report describes the method of predicting the luminous flux of light-pipes and also proposes methods of calculating, for overcast skies, the illuminance resulting from a given luminous flux. All data used has been obtained from measurements in the UK throughout the year for various locations. The data is therefore the result of actual sky conditions.