In this issue, Dave Hollingsbee introduces the Good Light Group – an organisation focused on the impacts of lighting on human health.

Keen eyed regular readers of this column will notice that the usual GreenLight Alliance logo has been swapped with that of the Good Light Group.

This in no way suggests that the work is all done when it comes to sustainability. While it is true that huge progress has been made over the past five years: terms like “harmonised metric” are known and understood, as are LCAs and EPDs; many readers likely have encountered TM66 and TM65.2 metrics; and remanufacturing (rather than buying new) has become mainstream. The tide may finally be turning on Cat A fit outs too.

Expect to see more on these topics and case studies, in the future, but now we share the stage with another vitally important topic within our sector, and it is not unrelated: Light and Health.

By light and health, we don’t just mean “tuneable white”, “warm dim”. These are nice features but arguably have muddied the waters or distracted from the real issues. Truly “human centric” or “circadian” lighting is about much more than simply dimming and dropping CCT as the day goes on. Warm dim could be argued to be the equivalent of boiling sustainability down to just recycling. It’s a start, but there is so much more to understand.

It is important that we do. Just as our industry has improved impressively in terms of light LED source efficiency (the inescapable lm/W) and sharpened up aspects like colour rendition, optical control and controls – there remains an elephant in the room.

There is a growing body of evidence pointing to myriad threats to human wellbeing if we don’t alter the way we approach artificial indoor lighting. Conversely, with this technology, and by interpreting the evidence correctly, there is unprecedented opportunity for parties all across our industry to intervene intelligently and positively.

It is a large, complicated and evolving subject. So, this is where we bring in the Good Light Group (and the closely affiliated Good Light Group Asia).

The Good Light Group exists as non-profit organisation operating globally, with a legal structure as a foundation, registered in 2019. Its main objective is to gather and interpret precisely these facts, and to promote the exposure to healthy light across all sectors. To establish and promote the benefits of natural daylight and electric lighting that compensates for its absence, as well as the health risks associated with spending all day indoors, where the light is normally too dim during the day and too bright in the evening.

Affiliated scientists work together with lighting designers to inform on the practical implementation of the latest research developments.

Founded in 2019, it is funded by individual members and commercial sustaining members. The group seeks to promote science-backed, actionable interventions for Healthy Light. The backbone of the group is its 33 Science Advisors from around the world.

The group share fantastically informative newsletters, host webinars with its experts and guest speakers. It issues very accessible videos, brochures and infographics.

In coming issues, we will explore a variety of fascinating and important studies, recommendations, emerging data and case studies. We will introduce eminent scientists working in this area, share papers and recommend further reading and viewing resources. But for this first issue, the Good Light Group founder Jan Denneman starts unapologetically by answering WHY? Never mind the ethics, or the science for now, how do I sell it to the bean-counters?

From €3 to €300: The Greatest Missed Opportunity in Lighting

Lighting’s Established Narrative

Indoor lighting is typically positioned in three ways. First, as functional infrastructure. Light is required to perform visual tasks; it must comply with standards, deliver sufficient illuminance on the task plane, limit glare and ensure visual comfort. Second, lighting supports architectural quality. It reveals materials, articulates texture and volume, structures space and shapes atmosphere. It is the medium through which architecture becomes perceptible and meaningful. Third, lighting is framed as sustainable. LED technology has drastically reduced energy consumption, intelligent control systems minimise unnecessary operating hours, and luminaires are increasingly designed with circularity, reuse and reduced embodied carbon in mind.

All three perspectives are valid. Without adequate light, we cannot function visually. Without well-designed light, architecture loses expression. Without energy efficiency and material responsibility, lighting is not future-proof. Yet a fourth dimension is largely absent from the discussion: the influence of light on human performance. Economically, this dimension outweighs the other three combined.

The Economic Blind Spot

The 3-30-300 rule makes this imbalance visible. Popularised by real estate advisor JLL, it describes the typical annual cost structure of an organisation and the building it occupies as approximately €333 per square foot per year, roughly equivalent to €333 per tenth of a square metre per year. Of this amount, approximately €3 relates to utilities such as energy and water, around €30 covers rent or capital costs, and roughly €300 accounts for personnel expenditure. While exact figures vary by country and sector, the proportions are remarkably consistent.

In offices, schools, healthcare facilities and industrial environments, people represent by far the largest cost component. Salaries, social contributions, recruitment, training, turnover, absenteeism and productivity losses due to fatigue or illness dominate operational expenditure. Yet the lighting industry continues to position itself primarily within the smallest category. Lighting is typically presented as an energy-saving measure, and investment decisions are frequently evaluated on the basis of payback periods derived from electricity costs. From an economic perspective, this focus is disproportionate.

The LED Success Story… and Its Consequence

Two decades ago, this emphasis on energy was understandable. Lighting accounted for approximately 15-18% of total electricity consumption. Improvements in efficiency delivered meaningful financial savings and carbon reductions. The transition to LED technology has fundamentally changed this landscape. High luminous efficacy, improved optical performance and advanced control strategies have reduced lighting’s share of total electricity use in many modern office buildings to only a few percent.

Technologically, this is a success story. Economically, however, it has reduced the relative leverage of further energy savings. Even an additional 10-20% reduction in lighting energy consumption has a modest financial effect when compared to overall personnel costs. The strategic leverage of lighting no longer lies primarily in the €3 category.

The 1% That Changes Everything

Consider a simple scenario: An organisation with 1,000 employees and average total personnel costs of €60,000 per employee per year has an annual payroll of €60m. A 1% improvement in productivity, or a 1% reduction in absenteeism-related costs, represents €600,000 per year. In many buildings, this exceeds not only the total annual energy cost of lighting, but often the total energy cost of the building itself.

When a marginal improvement in human performance outweighs the financial impact of eliminating the entire lighting energy bill, it becomes difficult to justify evaluating lighting primarily on the basis of energy efficiency. It would be comparable to assessing an orchestra by the weight of its instruments rather than by the quality of its performance. Efficient instruments matter, but the purpose of the orchestra is the music. In buildings, that performance is human performance.

Light Beyond Vision

The economic argument is reinforced by developments in chronobiology. In 2002, researchers including David Berson and Ignacio Provencio identified intrinsically photosensitive retinal ganglion cells in the human eye. These cells contain the photopigment melanopsin and are particularly sensitive to short-wavelength light (around 480 nanometres). Unlike rods and cones, they project to brain regions responsible for regulating circadian rhythms, including the suprachiasmatic nucleus in the hypothalamus.

Research by George Brainard and Steven Lockley demonstrated how evening light exposure suppresses melatonin and shifts circadian timing. Charles Czeisler and colleagues documented the relationship between circadian misalignment and impaired cognitive performance. Till Roenneberg introduced the concept of social jetlag, describing the mismatch between biological rhythms and social schedules, with measurable consequences for wellbeing and productivity. These findings confirm that light is not merely a visual stimulus but a biological regulator.

The Indoor Light Mismatch

Modern indoor lifestyles often provide insufficient vertical illuminance at eye level during the day while exposing individuals to relatively bright and often blue-enriched light in the evening. This pattern differs significantly from the natural daylight cycle under which human physiology evolved. Research led by Mariana Figueiro and Mark Rea has attempted to quantify circadian stimulus in relation to vertical light exposure. Studies indicate that higher daytime circadian stimulus is associated with improved sleep quality and increased subjective alertness. Publications in the Journal of Clinical Sleep Medicine have linked greater workplace daylight exposure to longer and better sleep.

Sleep is a critical mediator in this relationship. Chronic sleep restriction is associated with reduced attention, impaired executive function and increased error rates. In knowledge-based environments, this translates into lower productivity and diminished creative capacity. In safety-critical contexts, it increases operational risk. If lighting environments support better circadian alignment and sleep quality, they indirectly influence performance outcomes. In economic terms, this shifts lighting firmly into the €300 category.

The Light Diet

In my work on light and health, I describe this dynamic as the “light diet.” Just as nutrition influences metabolic health, patterns of light exposure influence circadian regulation and overall functioning. While individuals increasingly monitor diet and physical activity, few consider the quality and timing of their daily light exposure. Yet light is one of the most powerful external regulators of human biology. Indoor lighting is therefore not neutral background infrastructure, but a structural determinant of wellbeing.

From Insight to Initiative

To translate these insights into practice, the Good Light Group was established as an independent, non-profit platform dedicated to promoting healthier indoor lighting. The organisation addresses not only circadian-supportive lighting, but the broader biological consequences of reduced daylight exposure in modern buildings.

While much of the recent discussion has focused on melanopic stimulation and circadian regulation, natural daylight provides a far richer spectral composition than most indoor environments. Contemporary buildings filter out ultraviolet B radiation that enables vitamin D synthesis in the skin, and significantly reduce exposure to near-infrared wavelengths that are increasingly being studied for their role in cellular and mitochondrial processes. The cumulative biological implications of spending most of our lives indoors under spectrally limited light environments are only beginning to be understood.

The Good Light Group operates at the intersection of science, design and industry. It seeks to make emerging research accessible to architects, lighting designers, developers and policymakers, while encouraging dialogue between chronobiologists, photobiologists and building professionals. Its aim is not to prescribe simplistic solutions, but to foster a broader understanding of light as a multi-dimensional environmental factor that affects human physiology beyond vision alone.

By advocating for daylight integration, adequate vertical light exposure, biologically informed electric lighting strategies and deeper investigation into full-spectrum light environments, the Good Light Group promotes a more comprehensive definition of what “good light” means in contemporary architecture. The objective is to move the conversation from compliance and energy metrics toward measurable human outcomes and long-term health resilience.

Rethinking Sustainable Design

Recognising lighting as part of the €300 category has direct implications for design. Daylight strategy should be integral to architectural conception rather than an afterthought. Façade design, orientation, spatial depth and glare management fundamentally shape indoor light conditions. Electric lighting should complement and reinforce natural circadian rhythms. Vertical illuminance at eye level deserves greater attention than horizontal lux values alone. Temporal variation and spectral composition should be aligned with time of day and functional requirements.

For the real estate sector, this perspective implies that investment decisions should not be based solely on energy performance. When personnel costs exceed real estate costs by an order of magnitude and energy costs by two orders of magnitude, it is econom-ically rational to treat indoor environmental quality as a strategic variable. ESG frameworks increasingly reflect this shift. The environmental dimension remains important, but the social dimension encompasses health and wellbeing. Certification systems such as WELL and Fitwel explicitly include circadian lighting and access to daylight within their assessment criteria.

Sustainability in Full Meaning

The point is not that light is a panacea. The point is that light is a controllable environmental variable with demonstrable biological effects, and that these effects carry economic consequences. Developers and investors who focus exclusively on energy performance reduce sustainability to a technical metric. True sustainability includes social sustainability.

A building that is energy efficient but leaves its occupants chronically fatigued or disengaged cannot be considered sustainable in the full sense of the word. Sustainability must therefore be defined more broadly. Lighting must be energy efficient. Luminaires should be designed for circularity, reuse and reduced embodied carbon. Manufacturing processes must become more sustainable. At the same time, lighting must contribute to healthy and resilient users.

This requires a different design approach. Daylight must be integrated from the earliest stages. Electric lighting must support rather than override natural rhythms. Vertical light exposure and temporal dynamics must be deliberately structured. Users should understand how light affects them, enabling more informed interaction with their environment.

The principal barrier to this shift is not technological but economic and cultural. Building owners invest, while tenants benefit from improved performance. As long as these interests remain disconnected, short-term capital expenditure will dominate decision-making. Nevertheless, change is visible. Organisations competing for talent increasingly recognise the importance of workplace quality. ESG metrics are expanding to include wellbeing indicators. Human performance is entering the sustainability conversation.

The move from €3 to €300 is not an argument against energy efficiency. It is an argument for proportionality. Lighting should not be understood solely as a cost item to be minimised, but as a strategic investment in people.

The question is not whether we can afford to design lighting that supports health and performance. The question is whether we can afford not to.

This series is curated by Dave Hollingsbee of Stoane Lighting,

dave@mikestoanelighting.com