A DAYLIGHT CRITERION ON SOLAR CONTROLS FOR COMPARING SKY RADIANCE MODELS

The obstruction of solar radiation by solar controls must be balanced with the required daylight contribution. Solar controls are characteri zed by the percentage of non-obstructed external radiance. The estimat ion of this radiance, particularly its diffuse component, depends on t he sky radiance distribution used. In this work, we have compared thre e models (isotropic, CIE clear sky and Perez) before deciding which on e is the most suitable for calculating natural light without forgettin g the aspect of energy. The incident energy on an aperture where solar control is installed and its daily factor (DF) are the two parameters that have been adopted to analyze the three models. The energy allows us to compare the models and the DI; allows us to discuss the weight of each part of the sky dome for each model. It is deduced that the is otropic model is not suitable for calculating the natural light availa ble in the presence of solar control. The small differences observed b etween the results obtained with the other two models justify the adva ntage of using Perez's model in calculations of natural illumination d ue to its simple formulation. Copyright (C) 1996 Elsevier Science Ltd.