Validation of spectral simulation tools for the prediction of indoor daylight exposure

Abstract

A growing area of research focuses on the relationship between ocular light exposure and the non-visual responses. In order to accelerate research on this topic and improve building design, reliable spectral simulation tools are needed. This study aims at validating two of them, Lark and ALFA, by comparing their outcomes against daylight measurements. The goal is to assess how reliable these tools are in predicting spectral irradiance under different skies for indoor spaces. While spectral irradiance can in principle be simulated with a similar accuracy as for photopic values, there are some caveats in the current versions of both platforms.

Development of a multichannel spectral simulation tool and experimental validation with different lighting scenarios

“…This error margin is consistent with our findings for all channels in the daylight scenario. 18 However, as our physical model was considerably simpler than that of the above-referenced study, we presume that this is the reason for the lower error in our results.…”

“…To our knowledge, only a limited number of studies investigated spectral simulations for daylighting. 17,18 Moreover, no studies that validate the N -step algorithm for the combination of daylighting and electric lighting were found in the literature.…”

Simulations of non-image-forming effects of light in building design: A literature review

“…One study found that Lark calculates spectral irradiance with most errors within a ±20% range in a neutrally coloured space under daylight. 78 The authors noted a reproducibility error in ALFA , unresolved at the time of their study. It was also shown that under clear sky conditions ALFA tends to overestimate the irradiance, 99 even though the spectral characteristics are well represented.…”

A simulation tool for building and lighting design considering ipRGC-influenced light responses

“…The 9-channel results of the 3 Radiance simulations are used by Lark 2.0 to derive the average spectral irradiance over each channel (Pierson et al, 2021). The spectral irradiance is extrapolated for every nanometer, assuming that it is constant within each channel and equal to the average.…”

“…Since Radiance performs simulations with a 3-channel resolution, Lark combines the results of three individual simulations, each for different parts of the visible spectrum. Validation studies showed that this approach can predict spectral irradiance indoors with a reasonable accuracy (most errors are within a ±20% range compared to physical measurements) under daylight conditions (Pierson et al, 2021). Although Lark offered the possibility to include spectral composition with a 9-channel resolution in lighting design, until now it did not allow to analyse the spatial and temporal characteristics of light.…”