Abstract Energy conservation is a fundamental requirement in buildings today. It is essential to use technology that integrates the thermal environment and the luminous environment to ensure indoor environmental quality. It is important to understand as accurately as possible the distribution of luminance and radiance of the daytime sky. Though the CIE Standard General Sky for sky luminance distributions has been recommended, a method of selecting 15 Sky Types was not shown. In this paper, the author tries to improve the previous All Sky Model based on IDMP measurement data from Osaka with the aim of a high accuracy estimation method for luminance and radiance distributions of sky. The appearances of the types of CIE Standard General Sky and the assignment in estimating types are shown based on the measurement data in Osaka. The improved All Sky Model and the validation of this improved model using the measurements in Osaka and Tokyo, Japan was introduced.