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The average daylight factor is one of the most widely used methods for predicting the internal illuminance due to daylight. It is a simple tool that can be used in the early stages of design and can give information about the luminous environment inside a room. This method is supposed to be used under overcast sky conditions. Expanding the use of the average daylight factor to other sky conditions will encourage the use of daylight in buildings. Several methods have been proposed for the prediction of daylight based on the CIE Standard General Sky. However, most of these methods aimed for a detailed estimation of the internal illuminance pattern. This paper aims to investigate the potential for using the average daylight factor method under the ISO/CIE Standard General Sky. [ABSTRACT FROM AUTHOR]

Optimum use of natural light in buildings requires knowledge of the luminance distribution of the sky. Since the introduction of the CIE Standard General Skies, several methods have been proposed to find the frequency distribution of sky types. This paper presents a method whereby the ratio of the luminances of two sky elements and the ratio of the luminance of one sky element to the horizontal illuminance can be used in the determination of sky type. [ABSTRACT FROM AUTHOR]

The CIE Standard General Sky divides the luminance distributions of skies into 15 types, ranging from overcast sky to clear sky. Finding the type of sky from the set of CIE Standard General Skies is a difficult task. This is due to the need for accurate luminance measurements over a long period of time because such data are not available in many regions around the world and to the difficulty in obtaining accurate readings for the zenith luminance. This study presents a method whereby the ratio of the vertical sky illuminance (or irradiance) on two surfaces or the ratio of vertical sky illuminance to the horizontal sky illuminance can be used to classify a sky into one of the CIE Standard General Skies. [ABSTRACT FROM AUTHOR]