Smart glazing and glare: a new twist
Glare from sunlight is a familiar problem for building occupants, especially when windows lack adequate shading. Modern smart glazing technologies aim to protect interiors by adjusting tint levels automatically, reducing overheating in summer and cutting excessive solar radiation. A common feature of many tinted glazing systems is a shift toward a blue tint as they regulate light transmission. But new research from the EPFL’s Laboratory of Integrated Performance in Design (LIPID) challenges a foundational assumption about how we perceive glare and brightness through colored glazing.
Challenging the spectral sensitivity baseline
All measurements used to characterize light, glare, and even material properties of glazing have traditionally relied on the V(λ) spectral sensitivity function. This century-old standard summarizes the average human eye’s response to different wavelengths and underpins lighting design, glare assessment, and many optical materials’ specifications. The LIPID study, funded by the Swiss National Science Foundation (SNSF) and published in Scientific Reports, presents evidence that could upend these long-standing practices.
Red light behaves like blue in glare perception
In a controlled, daylight-filled office, researchers examined glare under four color-filtered glazing conditions: red, blue, green, and neutral. They tested both low- and high-intensity daylight, asking participants to rate glare discomfort. Surprisingly, red glazing produced the highest perceived glare, beating blue and even green in some cases. This contradicts the conventional wisdom that blue light is most provocative for glare, a belief largely derived from studies on blue-enriched LED lighting and automotive headlamps.
Implications for glare models and standards
Lead author Sneha Jain and senior researcher Jan Wienold report that the findings reveal gaps in current glare models. “The glare from red glazing was a real surprise because it contradicts the literature,” Wienold notes. The study suggests that relying solely on photometric methods—those that quantify light based on visible brightness—can yield errors exceeding 50% in glare estimations for strongly colored light sources. In other words, color matters far more than many standards account for when it comes to perceived glare.
From color perception to practical glazing design
The results imply that colorimetric methods, which consider how humans perceive color and brightness across wavelengths, should be employed more broadly for glazing assessment. If red and other colors influence glare differently than assumed, designers may need to rethink material choices, tinting strategies, and dynamic shading controls. The goal is to protect interior comfort without compromising daylighting benefits or energy efficiency.
Future directions and ongoing work
The EPFL team is expanding this line of inquiry. Wienold has launched a four-year SNSF-funded project to quantify color-related glare effects across a wider color spectrum and to apply alternative experimental methods. The aim is to refine glare models, update standards, and ultimately guide the development of smarter glazing and lighting systems that respond to color, not just luminance.
What this means for occupants and industry
For building occupants, the study reinforces the importance of adaptable shading and glazing that accounts for color-dependent glare. For researchers and industry practitioners, it signals a need to integrate colorimetric evaluation into engineering practice and standards development. As glazing technology evolves toward more sophisticated, tint-variable solutions, understanding how different colors influence glare will be crucial to delivering comfortable, energy-efficient indoor environments.
