Climate-Based Daylight Analysis

The recent history of daylight evaluation has been one of diminishing areas ofapplication, and, in the eyes of design team colleagues, diminished relevance.A daylight factor evaluation was often undertaken as an afterthought, andrarely did the ndings have a substantive impact on the design. Similarly,from certain perspectives it seemed that fundamental areas of daylightingresearch were in the doldrums - continued reliance on the half-century olddaylight factor had, inevitably, led to a sense of stagnation in sectors of theresearch community.Two seemingly concurrent, but out-of-step and totally independent de-velopments are changing both the perceived importance and the nature ofdaylight evaluations. The rst is the increasing demand to demonstratecompliance at the design stage with recommended measures of building per-formance, e.g. the LEED rating system. The need for this appears to bewidely accepted throughout the developed world, and the rate of uptakeby practitioners is ever increasing in response to pressure and encourage-ment from governments, regulatory bodies, etc. For those striving to e ectgood daylighting design however, the race for compliance is by no means en-tirely good news because the recommendations are founded on schema thatignore fundamental parameters such as building orientation and prevailingclimate. The second development is a major advancement in the way thatdaylight evaluations are carried out. This advancement, called climate-baseddaylight modelling, can address the very real concerns that practitionersand researchers are now voicing regarding the high potential for ‘compliancechasing’ resulting in poor design choices for buildings.This report contains: a brief overview of the history and practice of day-light evaluation as it is commonly carried out; a description of the newclimate-based schema for daylight modelling; a list of activities related tothe Reportership; and, a discussion of issues arising. It concludes with a rec-ommendation to continue these developments under the aegis of a full CIETechnical Committee on climate-based daylight modelling.