This article presents a novel experimental method that uses a virtual reality (VR) headset, aiming to provide an alternative environment for the conduction of subjective assessments of daylit spaces. This method can overcome the difficulty of controlling the variation of luminous conditions, one of the main challenges in experimental studies using daylight, and its novelty lies in the implementation of physically based renderings into an immersive virtual environment. The present work investigates the adequacy of the proposed method to evaluate five aspects of subjective perception of daylit spaces: the perceived pleasantness, interest, excitement, complexity, and satisfaction with the amount of view in the space. To this end, experiments with 29 participants were conducted to compare users’ perceptions of a real daylit environment and its equivalent representation in VR and test the effect of the display method on the participants’ perceptual evaluations, reported physical symptoms, and perceived presence in the virtual space. The results indicate a high level of perceptual accuracy, showing no significant differences between the real and virtual environments on the studied evaluations. In addition, there was a high level of perceived presence in the virtual environment and no significant effects on the participants’ physical symptoms after the use of the VR headset. Following these findings, the presented experimental method in VR seems very promising for use as a surrogate to real environments in investigating the aforementioned five dimensions of perception in daylit spaces.

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 UGR_exp, to achieve metrics that also perform reliably in dimmer lighting conditions than the ones explored in this study.

Temperature–color interaction effects on subjective perception and physiological responses are investigated using a novel hybrid experimental method combining thermal and visual stimuli from real and virtual reality (VR) environments, respectively. Despite potential building design applications, studies combining temperature with daylight transmitted through colored glazing are limited due to hard-to-control light conditions. VR is identified as a promising experimental tool for such investigations that overcomes the limitations of experiments using daylight. Fifty-seven people participated in an experiment combining three colored glazing (orange/blue/neutral) and two temperatures (24°C/29°C). Exposed to one color–temperature combination, participants evaluated their thermal, visual, and overall perception, whereas their physiological responses (heart rate, skin conductance, and skin temperature) were continuously measured. Daylight color significantly affected thermal perception, whereas no significant effects of temperature on visual perception were found. Acceptability of the workspace was affected by both color and temperature. Cross-modal effects from either daylight color or temperature levels on physiological responses were not observed. In the VR setting, the orange daylight led to warmer thermal perception in (close-to-) comfortable temperatures, resulting in a color-induced thermal perception and indicating that orange glazing should be used with caution in a slightly warm environment. Findings can be applied to the design of buildings using new glazing technologies with saturated colors, such as transparent photovoltaics. Despite some limitations, the hybrid environment is suggested as a promising experimental tool for future studies on indoor factor interactions.