The need for standard skies and models for energy conservation measures

Abstract

Historically, several standard skies have been adopted which enabled the development of calculation/prediction methods used in daylight design. Only recently have the scanning sky radiance/luminance meters made possible automated quick and precise routine measurements of sky distributions. The large data records gathered for various locations and time intervals stimulate their evaluation by computer based statistics. Thus sky classification systems, sky types and models based on averaged data were evolved. Due to their concepts and data base these sometimes question the validity of the general and simple CIE standard skies defined in accordance with theoretical and practical needs and established on chosen critical or extreme instantaneous states of the atmosphere. This paper discusses current queries on the basis of gradation scattering indicatrix analysis, being the theoretical basis of the sky models, and provides a comparison and representation of physically sound evidence compiled from measurements. Finally, due to the requirements of energy-conscious issues and design criteria the need for a set ofaverage sky types is stressed.