Occupants visual comfort assessments: A review of field studies and lab experiments

Abstract Many daylight metrics are developed to assess different aspects of visual comfort in recent years. However, there are still some doubts about the robustness of these metrics. This paper presents a comprehensive and thorough analysis of 58 field studies and lab experiments (2012–2020), focusing on metrics used to predict occupants' acceptance and visual preference in indoor environments. The review first covers the methodology of studies. Second, the results are discussed in four main categories: 1) confounding parameters in visual comfort studies; 2) metrics’ accuracy; 3) newly defined metrics or modified versions of the existing ones, and 4) metric thresholds. Finally, the lessons learned and limitations of the existing studies and recommendations for future studies on visual comfort are presented. Going through the results of those studies focusing on finding a proper metric for visual comfort evaluations revealed some of the previous studies had limitations in the experimental, statistical, and equipment. Ignoring these issues may have biased the studies’ findings. According to results, there is still a lack of consensus on adequate illuminance thresholds. Moreover, due to the complexity of the visual comfort concept and occupants' perception dependency on diverse factors, there is no global glare metric that could be applied to various conditions. To address these gaps, this study presents future researches trends, including the development of comprehensive study protocols, long-term glare assessment, and refining metrics thresholds. The findings of this paper could help researchers facilitate the application of filed and lab studies in visual comfort studies.