Evaluating Non-visual Effects of Light: An Open Challenge for Designers

Light is a powerful stimulus capable of influencing and altering physiological, psychological, and behavioural dynamics such as endocrine and cardiovascular functions, alertness, and circadian rhythms. Despite extensive researches on human-centred lighting and on potential applications of integrated design, many attempts to combine design-specific demands for the visual task with circadian metrics are not immediately useful for designers. Considering morning hours, a typical office has been simulated with three LED luminaires settings (direct, direct/indirect, indirect), three correlated colour temperatures (CCTs) and three different wall reflectances to evaluate two different approaches to lighting design: in the first (called “visual design”) luminous fluxes were set to be compliant with EN 12464-1 standard and then the circadian effects were assessed; in the second (called “non-visual design”), luminous fluxes were modified in order to meet the minimum circadian metrics, suggested by The Lighting Research Center (LRC) and the WELL Building Institute, and the illuminance on the task area, as defined by EN 12464-1 standard, were assessed. The obtained results show how lighting sources spectral and spatial distributions, together with the environmental characteristics are to be carefully considered by designers to comply both visual and non-visual requirements.