Light, Health and the Built Environment

The Guy Foundation’s Space Health Programme aims to assess and better understand the effects of space travel on human health, particularly beyond low Earth orbit.

Life evolved over billions of years under the spectrally complete radiation of the sun. Natural sunlight shaped the evolution of human physiology and influences cellular bioenergetics, metabolism, endocrine function, immune responses, and circadian rhythms.

Today, however, many people spend about 90% of their time indoors, often in buildings which are comfortable and energy efficient, but which have fundamentally altered our relationship with light.

Current building regulations and architectural practices, specifically low-emissivity glazing and LED lighting, are resulting in a modern built environment that whilst energy-efficient, does not serve biological need. Increasing evidence suggests that modern glazing and lighting are creating a significant mismatch by reducing or eliminating wavelengths that have been present throughout human evolution, particularly ultraviolet and red and near-infrared light.

The Guy Foundation has prepared two reports that detail these fundamental concerns and consider how a more physiologically appropriate approach to light could make a significant contribution to improving public health and wellbeing. The main report sets out the implications for key sectors (including architecture, glazing, lighting design and healthcare). The companion scientific report sets out the underlying biological evidence and mechanisms.

The authors thank members of our interdisciplinary working group that supported the preparation of these reports.

To further address these issues, The Guy Foundation is:

Engaging with stakeholders across disciplines and sectors and stimulating discussion and action on aligning buildings and lifestyle with human biology. In 2025 The Guy Foundation convened a symposia series ‘2025 Autumn Series on Light’ – view the talks and Proceedings here. If you, or your organisation, would like to get involved, please contact us to find out more.
Establishing a research programme centred at The Guy Foundation Quantum Biology and Bioenergetics Laboratory to investigate how modern lighting and glazing technologies influence cellular function, with a particular focus on mitochondrial biology. Our research integrates origins of life, evolution, photobiology, bioenergetics, biophysics, architecture, and public health to explore how the indoor light environment impacts human health. We are currently looking for funding partners to help us advance this work which sits at the frontier of one of the most exciting and consequential fields in science. Contact us to find out more.

Reduced Exposure to Near-Infrared Light
Near-infrared radiation accounts for more than half of the solar energy reaching the Earth’s surface. Conventional white LEDs and low-E glazing significantly reduce or eliminate these wavelengths. Yet an increasing body of research suggests that red and near-infrared light interact with mitochondria, influencing cellular respiration, membrane potential, ATP production, redox signalling, and intracellular melatonin. Understanding how these wavelengths affect mitochondria, as well as cellular function more generally, represents one of the central questions of our programme.
Reduced Ultraviolet Exposure
Modern glazing blocks most ultraviolet radiation. Although excessive UV exposure is associated with well-established health risks, ultraviolet light also contributes to several important physiological processes, including vitamin D synthesis and nitric oxide release from the skin, which are beneficial to health. Determining the balance between protection and physiological requirement remains an important research challenge.
Circadian and Spectral Mismatch
Natural sunlight provides powerful biological signals that regulate the circadian system. By contrast, many indoor environments provide insufficient daytime light for robust circadian entrainment while simultaneously exposing occupants to excessive short-wavelength light during the evening. This mismatch has been associated with disrupted sleep, impaired metabolic regulation, altered hormonal signalling, and reduced wellbeing.

Light, Glazing and Lighting in the Modern Built Environment (The Guy Foundation, 2026).
Light and the Modern Built Environment – the scientific basis (The Guy Foundation, 2026).
Proceedings from the 2025 Autumn Series on Light (The Guy Foundation, Jan 2026).
In Defense of Sunlight: The Surprising Science of Sun Exposure (Rowan Jacobsen)

For further references, visit the Light section of our Useful Resources page.

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