This paper (part one of two) investigates the formulation of metrics for the nonvisual effects of daylight, such as entrainment of the circadian system and a maintenance of alertness. The body of empirical data from photobiology studies is now sufficient to allow us to develop preliminary non-visual lighting evaluation methods for lighting design. These effects have the potential to become a relevant quantity to consider when assessing the overall daylighting performance of a space. This paper (Part I) describes the assumptions and general approach that were developed to model occupant exposure to nonvisual effects of light, and presents a novel means of visualizing the 'circadian potential' of a point in space. The proposed approach uses outcomes of photobiology research to define threshold values for illumination in terms of spectrum, intensity, and timing of light at the human eye. These values are then translated into goals for lighting simulation, based on vertical illuminance at the eye, that -ultimately -could become goals for building design. A new climatebased simulation model was developed to apply these concepts to a residential environment, described in Part II (forthcoming). 3 IntroductionThe primary concern in the daylighting of buildings has generally been to provide illumination for task, for example to ensure that 500 lux falls on the horizontal work plane. Although climate-based daylight modeling is over a decade old 1,2 , building guidelines and recommendations worldwide are still founded on idealized, static sky conditions such as the CIE standard overcast sky (i.e. to predict daylight factors). It is only recently that daylight metrics founded on climate-based simulations have begun to be considered as the basis for the next generation of building guidelines 3 , thus enabling a more realistic and location-specific evaluation of daylighting potential. In the last decade, there has also been a gradual increase in awareness of the non-visual effects of daylight (or more generally light) received by the eye 4 . It is well-known that building occupants almost without exception will prefer a workstation with a view of the outdoor environment to a windowless office 5 . A view to the outside of course indicates the presence of daylight, although the relation between view and daylight provision is not straightforward as it is dependent on many factors.In addition to subjective preferences for daylit spaces, it is now also firmly established that light has measurable neuroendocrine and neurobehavioral effects on the human body, in particular with respect to ensuring a healthy sleep -wake cycle and maintaining alertness. Could the quality and nature of the internal daylit environment have a significant effect on human health?Evidence is indeed suggestive of links between daylight exposure and both health and productivity 6 .The daily cycle of day and night plays a major role in regulating and maintaining 24-hour rhythms in many aspects of our physiology, metabolism 4 and behaviour.. These daily...

This study describes the development and validation of a Radiance model for a translucent panel. Using goniophotometer data combined with integrating sphere measurements, optical properties of the panel were derived and converted into a and integrating sphere measurements can be used to accurately model arbitrary translucent materials in Radiance using transdata function files.

Recent studies have attempted to link environmental cues, such as lighting, with human performance and health, and initial findings seem to indicate a positive correlation between the two. Light is the major environmental time cue that resets the human circadian pacemaker, an endogenous clock in the hypothalamus that controls the timing of many 24-hour rhythms in physiology and behavior. Insufficient or inappropriate light exposure can disrupt normal circadian rhythms which may result in adverse consequences for human performance, health and safety. This paper addresses the problem of prospective analysis of building architecture for circadian stimulus potential based on the state of the art in photobiology. Three variables were considered in this analysis: lighting intensity, timing, and spectrum. Intensity is a standard design tool frequently used in illuminating engineering. Timing and spectrum are not commonplace considerations, so the analysis that follows proposes tools to quantitatively address these additional requirements. Outcomes of photobiology research were used in this paper to define threshold values for illumination in terms of spectrum, intensity, and timing of light at the human eye, and were translated into goals for simulation-and ultimately for building design. In particular, the climate-based Daylight Autonomy (DA) metric was chosen to simulate the probabilistic and temporal potential of daylight for human health needs. The developed method was applied to study the impact of key architectural decisions on achieving prescribed stimulus of the circadian system in a hospital patient room design; studied variables included orientation, window size, and glazing material. A healthcare setting was specifically chosen with the intent of follow-on research to validate our findings with actual patient outcome data.

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.

This study evaluates the performance and robustness of 22 established and newly proposed glare prediction metrics. Experimental datasets of daylight-dominated workplaces in office-like test rooms were collected from studies by seven research groups in six different locations (Argentina, Denmark, Germany, Israel, Japan and the United States). The variability in experimental setups, locations and research teams allowed reliable evaluation of the performance and robustness of glare metrics for daylight-dominated workplaces. Independent statistical methods were applied to individual datasets and also to one combined dataset to evaluate the performance and robustness of the 22 glare metrics. As performance and robustness are not established in literature, we defined performance as: (1) the ability of the metric value to describe the glare scale (evaluated by Spearman rank correlation), and (2) the ability of the metric to distinguish between disturbing and non-disturbing situations (evaluated by diagnostic receiver operating characteristic curve analysis tests). Furthermore, we defined robustness as the ability of a metric to deliver meaningful results when applied to different datasets and to fail as few as possible statistical tests. Average Spearman rank correlation coefficients in the range of 0.55–0.60 as well as average prediction rates to distinguish between disturbing and non-disturbing glare of 70–75% for several of the metrics indicate their reliability. The results also show that metrics considering the saturation effect as a main input in their equation perform better and are more robust in daylight-dominated workplaces than purely contrast-based metrics or purely empirical metrics. In this study, the daylight glare probability (DGP) delivered the highest performance amongst the tested metrics and was also found to be the most robust. Future research should aim to optimise the terms of glare equations which combine contrast and saturation effects, such as DGP, PGSV or UGRexp, to achieve metrics that also perform reliably in dimmer lighting conditions than the ones explored in this study.

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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.