This paper introduces a novel approach for the assessment of daylight performance in buildings, venturing beyond existing methods that evaluate 2-dimensional illumination and comfort within a fixed field-of-view in order to predict human responses to light concerning non-visual health potential, visual interest, and gaze behavior in a visually immersive scene. Using a 3D rendered indoor environment to exemplify this coordinated approach, the authors assess an architectural space across a range of view directions to predict non-visual health potential, perceptual visual interest, and gaze behavior at the eye level of an occupant across an immersive field-of-view. This method allows the authors to explore and demonstrate the impact of space, time, and sky condition on three novel daylight performance models developed to predict the effects of ocular light exposure using a humancentric approach. Results for each model will be presented in parallel and then compared to discuss the need for a multi-criteria assessment of daylight-driven human responses in architecture. A parallel and comparative approach can allow the designer to adapt the architectural space based on the program use and occupants needs.

Daylit architecture is perceived as a dynamic luminous composition, yet most existing performance metrics were designed to evaluate natural illumination for its ability to adequately illuminate a twodimensional task surface and avoid glare-based discomfort. It may be argued that task-driven approaches based on surface illumination and glare ignore the likelihood that contrast can provide positive impacts on our visual perception of space. Advances in these metrics to accommodate climate-based sky conditions and occupant behavior have improved our ability to evaluate task illumination and glare, yet the same attention has not been paid to evaluating positive perceptual responses to daylight. Existing studies have attempted to link subjective ratings of composition to simple global contrast metrics without reaching consensus. More advanced metrics have been developed in computational graphics and vision fields, but have not been applied to studies in qualitative lighting research. This paper introduces the results from an online experiment where subject ratings of daylight composition are compared to quantitative contrast measures across a series of renderings. This paper will identify which measures correlate to subjects' ratings of visual interest, and introduces a modified contrast algorithm, which can be used as a novel prediction model for visual interest in daylit renderings.

The discovery of a novel non-rod, non-cone photoreceptor in the mammalian eye that mediates a range of 'non-visual' responses to light has required reexamination of how lighting needs for human health are characterized and evaluated. Existing literature provides useful information about how to quantify non-visual spectral sensitivities to light but the optimal approach is far from decided. As more is learned about the underlying biology, new approaches will continue to be published. What is currently lacking is a flexible framework to describe the non-visual spectral effectiveness of light using a common language. Without a unified description of quantities and units, much of the value of scientific publications can be lost. In this paper, we review the existing approaches by categorizing the proposed quantities depending on their application. Based on this review, a unified framework is provided for use in evaluating and reporting the spectral effectiveness of light for human health. The unified framework will provide greater flexibility to model the non-visual responses to light and is adaptable to a wide range of lighting solutions of interest for researchers, designers and developers. A new visualization tool, the SpeKtro dashboard, is available to explore the unified framework on-line at spektro.epfl.ch.

Human circadian, neuroendocrine, and neurobehavioral responses to light are mediated primarily by melanopsin-containing intrinsically-photosensitive retinal ganglion cells (ipRGCs) but they also receive input from visual photoreceptors. Relative photoreceptor contributions are irradiance- and duration-dependent but results for long-duration light exposures are limited. We constructed irradiance-response curves and action spectra for melatonin suppression and circadian resetting responses in participants exposed to 6.5-h monochromatic 420, 460, 480, 507, 555, or 620 nm light exposures initiated near the onset of nocturnal melatonin secretion. Melatonin suppression and phase resetting action spectra were best fit by a single-opsin template with lambda max at 481 and 483 nm, respectively. Linear combinations of melanopsin (ipRGC), short-wavelength (S) cone, and combined long- and medium-wavelength (L+M) cone functions were also fit and compared. For melatonin suppression, lambda max was 441 nm in the first quarter of the 6.5-h exposure with a second peak at 550 nm, suggesting strong initial S and L+M cone contribution. This contribution decayed over time; lambda max was 485 nm in the final quarter of light exposure, consistent with a predominant melanopsin contribution. Similarly, for circadian resetting, lambda max ranged from 445 nm (all three functions) to 487 nm (L+M-cone and melanopsin functions only), suggesting significant S-cone contribution, consistent with recent model findings that the first few minutes of a light exposure drive the majority of the phase resetting response. These findings suggest a possible initial strong cone contribution in driving melatonin suppression and phase resetting, followed by a dominant melanopsin contribution over longer duration light exposures.

The discovery of a novel non-rod, non-cone photoreceptor in the human eye that mediates a number of effects on the brain has sparked a growing interest in incorporating these non-visual effects of light into the design process of buildings. Appropriately-timed light exposure has the potential to stabilize and improve circadian rhythms, including sleep, and has direct stimulating effects on alertness and performance. The novel photoreceptors are more sensitive to blue light than the rods and cones used for vision, and respond differently to light intensity, duration, history and timing of a light exposure. The dynamic behavior of the non-visual system provides new challenges in evaluating lighting performance of buildings. In this proof-of-concept study, a novel model that predicts the non-visual responses to light is introduced. The model is used as a part of simulation-based framework for the evaluation of daylighting performance. The evaluation includes four different light pattern generation methods used to investigate the influence of occupants' movements and activities on simulation results. The framework is applied to the re-design of a healthcare facility. The results lead to new ideas and suggestions for future re-design.