October 31, 2023   

Evaluating Glare and Discomfort in Bright Spaces

2023 10 Evaluating Glare and visual Discomfort in Bright Spaces office lighting design.jpg

A comprehensive study sheds light on the complexities of glare perception


In the realm of daylit workspaces, where light is both a blessing and a potential curse, the concept of "discomfort glare" often lurks in the background, impacting productivity and well-being. A recently published study by a team of researchers dives deep into the nuances of how we perceive and evaluate this glare, offering insights that could shape the future of lighting design and workplace comfort.

At the crux of this research lies a seemingly simple tool: the questionnaire for the building occupant. Yet, as the study reveals, this basic instrument holds complexities that can significantly influence how discomfort glare is understood and managed. The team of scientists meticulously examined the reliability and consistency of various questionnaire items, typically used to gauge individuals' discomfort in light-filled environments. Their findings have crucial implications for architects, lighting designers and workplace planners striving to balance luminosity with comfort.


The Science Behind the Survey: A Closer Look

Imagine walking into a brightly lit office space and feeling that slight squint forming in your eyes. Is it merely noticeable, or is it discomforting? This is the kind of subtle distinction the study aimed to capture. The researchers compared six types of questionnaire items, ranging from simple binary "Yes/No" options to more nuanced scales asking participants to rate their discomfort. Surprisingly, the results were more consistent than one might expect. Despite the diversity in questionnaire formats, participants' responses showed strong correlations, suggesting that these varied tools essentially tap into the same underlying sensation of glare-induced discomfort.


Better than Binary: More Than Just Yes or No

A particularly intriguing aspect of the study involved binary questionnaire items. While these simple "Yes/No" questions correlated well with more detailed scales, they tended to reflect higher thresholds of discomfort. In other words, if you're looking to detect subtle levels of glare-induced annoyance, a simple "Yes/No" might not cut it. This finding is especially pertinent for environments where even mild discomfort glare could be detrimental, such as in high-precision workspaces or art studios.



Source: "A critical analysis of questionnaire items for discomfort glare studies in daylit spaces"


The study also highlighted that the specific wording and structure of questionnaire items could subtly influence how people report their discomfort. For instance, a scale asking whether the light is "noticeable" versus "disturbing" might elicit different responses, despite both aiming to measure discomfort. This semantic sensitivity is a crucial consideration for researchers and designers alike, emphasizing the need for carefully crafted questions that accurately capture the intricacies of human perception.


Tapping into prior work from PNNL and IES

Among the research pieces cited in the study was "Correspondence: A new two-step approach for evaluating discomfort from glare" by Kathryn S. Hickcox, Steve Fotios, Belal Abboushi, and Naomi J. Miller from the Pacific Northwest National Laboratory (PNNL), Portland, OR, USA, and the University of Sheffield, Sheffield, UK. This work proposed an alternative to the de Boer scale, introducing a novel two-step approach for evaluating discomfort from glare.

The study published last week focused on selecting and comparing six questionnaire items for evaluating discomfort from glare in rating-type experiments, of which the 'two-step approach' rating scale was a part. The foundation for the PNNL research stemmed from the efforts of the Illuminating Engineering Society DGONE Committee.


Practical Implications: Lighting Design and Beyond

The findings of this study seem to provide tangible implications for anyone involved in designing or occupying lit spaces. For architects and lighting designers, the insights offer a more nuanced understanding of how different questionnaire tools can capture occupants' comfort levels. This knowledge could prove valuable in designing spaces that not only look good on paper but feel good to those inside them.

For workplace planners and managers, the research underscores the importance of considering glare not just as an afterthought but as a central element in creating comfortable, productive environments. In the age of open-plan offices and glass-walled buildings, managing daylight and its accompanying glare becomes a critical aspect of workplace wellness.



Geraldine Quek PhD, Sneha Jain PhD, Caroline Karmann PhD, Clotilde Pierson PhD, Jan Wienold PhD, Marilyne Andersen PhD from the Laboratory of Integrated Performance in Design (LIPID), École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland