Matching CIE illuminants to measured spectral power distributions: A method to evaluate non-visual potential of daylight in two European cities

Evaluation of Visual and Nonvisual Levels of Daylight from Spectral Power Distributions Considering Orientation and Seasonality

“…Bella et al [17] modelled the nonvisual potential of daylight in terms of the melanopic/ photopic ratio calculated from the SPD, finding values very close to 1 and similar to those calculated by using the D 40 to D 120 illuminances. Although this definition differs from our MAF, both indicate practically the same melanopic contribution as the photopic for daylight, and the spectra could be considered to be covering similar ranges to our CCTs.…”

“…Bella et al [17] modelled the nonvisual potential of daylight in terms of the melanopic/photopic ratio calculated from the SPD, finding values very close to 1 and similar Both the photopic illuminances and EMLs reach higher illuminances in the east and south orientations and in the summer months, as is the case with the EDIs that can be calculated according to the relation EML = 1.104 EDI. The minimum illuminances, both photopic and melanopic, were taken in December at a west orientation with an angle of 15 • .…”

“…This situation will be favourable for improving indoor performance in the morning hours; however, in the afternoon and at night, it will be more convenient to use warm lighting with low melanopic intensity [9,15]. In an investigation of a method to evaluate the nonvisual potential of daylight in two European cities, CCTs between 4631 K and 11,871 K were recorded in Naples and CCTs between 3585 K and 9812 K were recorded in Bialystock [17]. These results are similar to those of this study since our CCT measurements vary between 4892 and 12,380 K. However, due to the low correlation between the CCT and circadian effects, it is considered that the CCT is not a good indicator to establish the levels of circadian response [20,37].…”

“…An important issue found for accurate visual and nonvisual daylight implications is the limited information available for this analysis because at least six factors triggering nonvisual light effects have been summarized, including the SPD, the irradiance level, the directionality, the timing, the duration, and the history, which are grouped into luminous and temporal categories [11]. Nevertheless, there have been efforts to develop a clear method to evaluate the effects of lighting on circadian rhythm regulation from different perspectives [17,18].…”

“…This research hypothesizes that daylighting SPDs modify the photopic and melanopic levels inside buildings depending on the orientation, seasonality and characteristics of the skydome [17,18]. The aim of this study is to analyse these real seasonal changes in natural sunlight to evaluate how changes in the SPD affect photometric quantities and calculate the variations in circadian magnitudes based on the CIE standard.…”