Circadian stimulus calculators as environmental building design tools: Early results of a critical review

Lighting is a hugely important aspect of the environmental building design. During the past decades the building industry has been primarily concerned with the illuminance and the energy efficiency part of the artificial lighting rather than the human health. Latest studies emphatically state that a proper lighting design and luminaire types should promote the circadian rhythm. In the present study the differences between two available Circadian Stimulus CS calculator algorithms are identified. More analytically the CS calculators are applied to a number of measured spectral power distributions (SPD) of a commercial tunable white LED luminaire (2000K-6500K). The different impact between the CS calculators for the same measured spectral power distributions is concluded through the evaluation and comparisons of the results. The different results of the CS estimations for the same SPD could affect significantly the circadian lighting design and the proper selection of a luminaire.