Estimation of point daylight factor (PDF) average daylight factor (ADF) and vertical daylight factor (VDF) under various obstructed CIE standard skies

Abstract

Estimation of the daylight level for any point within an interior space is essential to daylighting designs and assessments. In 2003, the CIE adopted a range of 15 skies as international standard models that represent the actual skies of many places and cover the whole probable spectrum of skies. In many urban cities, the external obstructions may significantly reduce the amount of daylight entering to the indoor space. Previously, we developed a number of calculation tools to predict daylight illuminance for rooms facing different orientations under various CIE Standard Skies. This paper presents the work on the calculation of the PDF, ADF and VDF under various overcast and non-overcast obstructed skies. Calculation procedures are demonstrated. Characteristics of the findings and design implications are discussed.