Utilization of daylight in school buildings

Nowadays, daylighting in interiors of school buildings is evaluated after model representing CIE overcast sky conditions. During a year also other situations can occur which are not respected in the design of interior daylighting. The work group WG11 of the CEN TC 169 elaborates the EN standard for evaluation of daylight in buildings considering also local climate in Europe. One of the proposed parameters for determination of exterior daylight conditions is median of exterior diffuse illuminance which can be obtained either from the satellite data or from regular ground measurements.