New Findings Challenge a Century of Lighting Standards
Glare from sunlight is a daily concern for occupants and designers in offices, classrooms, and homes. It can lead to discomfort, reduced productivity, and even visual fatigue. For years, glazing technology has aimed to minimize heat and glare through tinting that often shifts toward blue hues. This approach is grounded in conventional models of human light perception built around the spectral sensitivity function V(λ). But a recent study from EPFL’s Laboratory of Integrated Performance in Design (LIPID) throws the reliability of those models into question and could alter both research and practical design decisions in architecture and lighting engineering.
The Surprising Role of Red Light
Traditionally, glare studies emphasized blue wavelengths as the primary source of visual discomfort, a view reinforced by research on automotive LED headlights and other blue-dominated lighting. The EPFL/LIPID study, however, demonstrates that red light can produce glare effects comparable to blue under certain conditions. The research used four color-filtered glazing conditions—red, blue, green, and neutral—exposed to both low- and high-intensity daylight in a controlled, daylit office environment. Participants consistently reported the strongest glare under red glazing, followed by blue, with green producing the least disturbance among the colored filters.
Implications for Glare Modeling and Standards
The findings suggest that current glare models, which lean heavily on photometric approaches and the V(λ) function, may misestimate glare when strongly colored light is involved. Jan Wienold of LIPID explains, “The glare from red glazing was a real surprise because it contradicts the literature.” The study indicates potential deviations of more than 50% between measured glare and what traditional models predict, signaling a need for colorimetric methods when evaluating strongly colored light sources and glazing systems.
What does this mean for practice? Designers and researchers may need to revisit how they simulate daylighting. Relying solely on photometric metrics could lead to under- or over-designing shading and glazing solutions, particularly in spaces that use or encounter colored glazing or LED-based colored lighting. The study argues for integrating color-sensitive metrics into standard lighting analyses to better reflect human experience of glare in real-world conditions.
Towards Smarter Glazing and Safer Lighting
The researchers’ work aligns with broader trends in intelligent glazing: dynamic tinting that adapts to sunlight while protecting occupants from overheating and glare. By highlighting red and blue light as potent glare sources, the findings could guide the development of smarter, perceptually aware glazing that adjusts color and tint in response to changing daylight spectra. Such advancements would complement LED-based lighting systems, enabling more comfortable, productive indoor environments without compromising daylight access.
Future Research and Practical Steps
With funding from the Swiss National Science Foundation (SNSF), Wienold and his team have launched a four-year follow-up project. The goal is to quantify the observed effects across additional colors and to employ supplementary experimental methods, seeking to generalize the results beyond the test conditions. For practitioners, the takeaway is clear: skepticism toward a one-size-fits-all glare metric and openness to colorimetric evaluation are essential as glazing technologies evolve.
What to watch for next
Expect updates to glare modeling frameworks that account for color-dependent discomfort, alongside refinements in standards that govern glazing performance. As smart glazing becomes more prevalent, we may see more nuanced shading controls that not only lower heat transfer but also optimize perceptual comfort across daylight conditions.
In sum, red light’s glare punch redraws the map for glazing design and lighting science. If replicated, these results could lead to smarter glass and smarter light, benefiting occupants and the built environment alike.
