Light & Engineering Vol. 23, No. 1, pp. 4-14, 2015 Svetotekhnika No. 5, 2014, pp. 37-45 CLASSIFICATION OF DAYLIGHT CONDITIONS IN CLOUD COVER SITUATIONS Darula Stanislav and Kittler Richard Institute of Construction and Architecture, Slovak Academy of Sciences, Bratislava E-mails: usarsdar@savba.sk; usarkit@savba.sk ABSTRACT Daylight is widely used for the illumination of workspaces and residential interiors the whole year round. <...> Measurements of exterior illuminance at CIE IDMP stations show high va riability of daylighting from sunrise to sunset. <...> The changes of sun height, cloud type and cloud cover as well as the turbidity of the atmosphere infl uence levels of day light availability and daily illuminance sequences. <...> To design and simulate daylighting in buildings the typical exterior conditions are needed. <...> The cloud type, cloud cover and sunshine duration can determine va rious types of clear, cloudy and overcast days. <...> The study of global and diffuse illuminance sequences based on measurements shows that six types of daily illuminance courses can be classifi ed for daylighting and illuminating engineering calculations. <...> This paper discusses the infl uence of cloudiness on daily illuminance sequences. <...> Interiors can be illuminated by daylight and/or artifi cial light. <...> While artifi cial light ensures stable luminous conditions during the whole operating time, daylight is permanently changing from sunrise to sunset every day across the year, which is its advantage. <...> Currently, the criteria for design rules are based on the CIE recommendations [1] presenting the worst luminous exterior conditions by sky luminance distribution of overcast sky after [2 ]. <...> Kittler in [3] introduced a model of general sky describing a set of homogeneous sky luminance patterns adopted by ISO as the standard ISO 15469:2004, [4]. <...> Several authors [5 - 12] realised that a lot of cloudy and sunny skies with various types of cloud cover and atmospheric turbidity can occur in all climatic zones on the Earth, and they affect irradiance and illuminance availability. <...> The classifi cation of cloud types for meteorological purposes has long been established and elaborated upon, e.g. in [13 - 15]. <...> Detailed information about occurrence of daylight during various cloudy daily conditions were obtained recently <...>