Due to an increasing demand for an improvement in environmental conditions for living and a need for energy saving, development of daylight exploitation products has accelerated. The invention of light-pipes which bring natural light indoors where sunlight cannot reach without generating excessive heat is one such example. Mathematical modelling activities aimed at predicting the daylighting performance achievable by light-pipes with various con gurations under all weather conditions in the UK are being undertaken. Two models, one for straight light-pipes and the other for elbowed light-pipes are described. The models enable estimation of daylight provision of the light-pipes with a high degree of accuracy i.e., R 2 values of 0.95 and 0.97 for regression between predicted and measured illuminance were respectively obtained for the above models. The maximum Mean Bias Error (MBE) and Root Mean Square Error (RMSE) were -2 lux and 27 lux. A design guide for light-pipe assessment is presented that will obviate the need for use of mathematical models.

Predictive models of building performance are increasingly being based on sky luminance and radiance distributions. These, though, tend to exist as separate records and the word-wide coverage is not complete: sky luminance, in particular, has been recorded at relatively few locations. It is important in practice to ensure that luminance and radiation values are consistent with each other and that radiation measurements are used to supplement the illumination records. The paper compares data from the authors’ research in several climatic regions and shows that an anisotropic model of the sky distribution can be significantly more accurate than an isotropic function. This is discussed with particular reference to shadow band correction.