The fifteen typical sky luminance patterns adopted by the International Standard Organisation define their relative homogeneous luminance distribution over the sky vault and predetermine illuminance levels outdoors. Specific cloud cover and type distributed in certain parts of the sky vault can also create different daylight illuminance on variously oriented house fronts. Meteorological information on daily cloud cover and type are usually only recorded at certain times, e.g. at 9, 14 and 19 h and correspond neither to minute or hourly data recorded by irradiance, illuminance or luminance sensors outdoors measured at the CIE IDMP stations link in Bratislava where records of vertical sensors oriented to four cardinal points are gathered. The importance of vertical daylight availability on oriented facades and window surfaces is the prior task of building science and daylight theory particularly. Due to orientation any facade is exposed to specific sky luminance variability patterns in real time which differ from daylight availability and condition changes. Nevertheless, investors, architects and builders are challenged to intuitively respect a myriad of natural differences of environmental conditions in their designs including different window shading devices or shelves. Few standards recommend real circumstances with impacts on interior daylighting and energy saving. (C) 2015 Elsevier Ltd. All rights reserved.