The rationale and implications of ensuring adequate daylight provision are considered for designing cities and buildings.

The World Health Organization lists universal access to clean air, clean water, nutritious food and safe shelter as key components of public health, Lisa Heschong (author, architectural researcher & a fellow of the Illuminating Engineering Society), argues that access to ample daylight, both outdoors and indoors, should be added to that list. Evidence from many different scientific fields¹ reveal that humans live healthier, happier, more productive lives with daily exposure to the natural patterns of sunlight.

Introduction

Historically, access to sufficient daylight and sunlight in our cities and buildings was easy to accomplish at low population densities. But with ever greater population densities, carefully planned urban infrastructure is needed to provide universal access. A hundred years ago, humans spent most of their daytime hours outside. The advent of electric lighting was considered a blessing that extended indoor functionality into the dark night hours, especially in winter, replacing dim candles and gas lamps. But our modern culture has adapted to the easy availability of electric light indoors, enabling factory shift work, retail hours extending long into the night, and the non-stop 24-hour global economy. Modern life is now conducted primarily indoors. Indeed, Americans spend over 90% of their lives indoors, leaving less than two hours per day outdoors.

With Earth’s population surpassing 8 billion, daily access to sunlight and daylight is no longer a given. Streets lined with high-rise buildings create dark urban canyons that rarely see the sun, while ever-larger buildings rely solely upon electrical systems to make their interiors habitable. We are just beginning to understand the public health impacts of this dramatic change in our luminous environment.

‘Healthy light’

A little over twenty years ago we first learned about how non-visual photoreceptors, called opsins, help to synchronize daily (circadian) rhythms of sleep, hunger, motivation, alertness and immune function. This discovery has been fueling an on-going revolution in lighting design: a new understanding that light is needed not only for visual performance, but also human health (Wirz-Justice et al. 2021). Importantly, these non-visual opsins² are uniquely sensitive to blue and blue-violet wavelengths, amply available in both sunlight and unfiltered window views of the outdoors, but generally deficient in electric light sources. Too little blue-rich light during the daytime, or too much at night, can result in circadian disruption; producing jet-lag like symptoms in the short term and increased risk of over 50 systemic diseases in the long term (Fishbein et al. 2021, Smolenski et al. 2015). Epidemiological studies have since established wide-ranging public health benefits, including better mental health (Burns et al. 2023), better eyesight (Dadvand et al. 2017, Yang et al. 2021), and even significantly lower overall mortality over the course of decades (James 2016), associated with spending more time outdoors, more exposure to ‘greenery’ or nature (Frumpkin et al. 2017), all of which may function as proxy indicators of daylight exposure.

Electric light use, on the other hand, has been found to change sleep patterns of traditional hunter-gather communities (de la Iglesia et al. 2015, Moreno et al. 2015).  In modern society, a recent study found that spending multiple days camping outdoors increased average daytime light exposure of participants by about one order of magnitude, compared to their work-a-day lives and reduced nighttime electric light exposure by 1-2 orders of magnitude. These changes returned participants to a more naturally-entrained circadian cycle (Wright et al. 2013, Stothard et al. 2013).

Most disturbing is new evidence suggesting that patterns of daylight exposure in early childhood can have life-time consequences. For example, too little daylight has been strongly associated with the development of childhood myopia, or nearsightedness, which is not reversable. In some Asian cities, where children spend an average of only 30 minutes a day outdoors, over 90% of high school seniors require lens correction for myopia (Houser 2021). Cognitive development can also be impacted. For instance, early neural development in mice has been shown to be stimulated by daylight exposure (Burger & Lang 2022, Hu et al. 2022). A study of preschoolers in Norway (Ulset et al. 2017) compared the cognitive performance of children who spent five or more hours per day outside than their peers. For each year that children spent mostly outdoors, they advanced an additional half a year on cognitive tests. By age six, the outdoors cohort tested two full years ahead of their indoor peers.

Studies of student performance in daylit elementary schools suggest that daylight or sunlight provision inside schools can have similar impacts. More daylight availability within classrooms was associated with greater annual progress on standardized tests (Heschong et al. 2002, 2003A). Likewise, larger windows with more interesting views also had similar benefits (Heschong et al. 2003B, Baloch et al. 2020). Similarly, a UK study found that, of 30 classroom design options considered, larger windows and views best predicted student academic progress (Barrett et al. 2015).

As a result of mounting evidence of the health benefits, newly published guidelines from the CIE (CIE 2023) and IES (IES 2023) recommend that daylight always be considered the primary source of stimulus for circadian and neurophysiological health. These guidelines set minimum standards for circadian stimulus indoors, based on vertical eye-level exposure to daylight.  

Daylight mimicry

These new guidelines would seem to be a clear win for more daylight in buildings.  However, most of the attention in the lighting industry has turned instead to methods to mimic daylight via electronic substitutes, from color-shifting LEDs for dynamic ambient lighting to the development of artificial windows and skylights. Manufacturers are eager to claim health and cognitive performance benefits for these products. However, regulators worry that the increased energy use of these electric devices may also threaten carbon reduction goals (Safranek et al. 2020). Meanwhile, field studies of dynamic electric lighting have not been able to translate lab findings into real-world worker performance. Thus, researchers warn: “the natural preference for daylight and tolerance for – or even appreciation of – its variability cannot be directly transferred to a preference for dynamic electric light” (Kompier et al. 2022).

For many building owners and developers ‘healthy (electric) lighting’ products conveniently offer the opportunity for cost savings, by enabling bigger and deeper buildings that provide occupants with little or no access to daylight. That was certainly the rationale for billionaire Charlie Munger in proposing his audacious design for a huge new dormitory for University of California Santa Barbara (UCSB), as revealed in 2021. This 1.68 million ft² building featured 9 floors of 4,500 identical windowless bedrooms, each just big enough for one single bed and one desk, and each with an LED-illuminated ‘fake’ window mounted high on the back wall (Heschong 2021). Following international furor and two years of protests, UCSB quietly canceled their plans (Niland et al. 2023).

The Munger Hall proposal was emblematic of similar campaigns all over the world by developers seeking permission to build windowless bedrooms, or entire windowless apartments as in Washington DC, Philadelphia (Avery 2023) and New York City (Relman 2023). Many cities have a housing crisis. For instance, housing prices in Honolulu, Hawaii, are some of the highest in the US, and encampments of the homeless population have been expanding along local streets and beaches. These conditions were used by developers in 2023 to argue for exceptions to local codes to retrofit empty office buildings into ‘affordable housing’, where half the units would be windowless (Downey 2023). Such compromises may seem to make logical sense in the short term; but long-term public health outcomes will slowly reveal their economic folly.

Conclusions

After the trauma of the Covid pandemic, I hoped that there would be a massive social shift demanding more naturally ventilated and daylit buildings. But instead, faced with a housing crisis, prohibitive construction costs, and the lure of new technologies, evermore schools, homes and workplaces are being housed in windowless buildings, both new and old. Inevitably, some of the poorest and most vulnerable will end up living or working there.

Market forces are not always particularly good at providing for long-term social benefits and so we need governmental policies that assure the health and well-being of all people. Thus, regulation is needed to ensure healthy urban landscapes are achieved: easy access to people-friendly streets, parks, school yards and rooftops that receive a minimum number of hours of sunlight per day. We need a revival of design standards for homes, schools and workplaces guaranteeing universal access to views of the sky and distant vistas. We need building codes that prioritize daylight illumination over electric illumination and that balance long-term health concerns alongside energy use. In short, it is time to recognize access to daylight as a basic human right.

Notes

1. Evidence about the benefits of natural light comes from the fields of epidemiology, chronobiology, ophthalmology, psychology, and embryology.

2. The role of melanopsin in circadian entrainment, the first non-visual opsin identified in the human retina in 1997, is well understood (Wirz-Justice et al. 2021). The functional roles of two other non-visual opsins, Neuropsin and Encephalopsin, which have recently been found in the retina and many other human tissues, are actively under investigation.

References

Avery, D.  (2023, March 24).  Wait, Are Windowless Bedrooms Going to Be a Thing? Architectural Digest. https://www.architecturaldigest.com/story/wait-are-windowless-bedrooms-going-to-be-a-thing

Baloch, R.M.,Maesano, C.N., Christoffersen, J., Mandin, C., Csobod, E., de Oliveira Fernandes, E., Annesi-Maesano, I. & SINPHONIE Consortium. (2020). Daylight and school performance in european school children. International Journal of Environmental Research and Public Health, 18(1), 258. https://doi.org/10.3390/ijerph18010258

Barrett, P., Davies, F., Zhang, Y. & Barrett, L. (2015). The impact of classroom design on pupil’s learning: final results of a holistic, multi-level analysis. Building and Environment 89, 118-133. https://doi.org/ 10.1016/j.buildenv.2015.02.013

Burger, C.A. & Lang, R.A. (2022). Illuminating brain development. Cell Research, 33, 89-90. https://doi.org/10.1038/s41422-022-00732-9

Burns, A.C., Windred, D.P., Rutter, M.K., Olivier, P., Vetter, C., Saxena, R., Lane, J.M., Phillips, A.J.K. & Cain, S.W. (2023). Day and night light exposure are associated with psychiatric disorders: an objective light study in >85,000 people. Nature Mental Health, 1, 853–862. https://doi.org/10.1038/s44220-023-00135-8

CIE. (2023). Technical Note: Second International Workshop on Circadian and Neurophysiological Photoreception. International Commission on Illumination, TN 015:2023. https://doi.org/10.25039/TN.015.2023

Dadvand, P., Sunyer, J., Alvarez-Pederol, M., Dalmau-Bueno, A., Esnaola, M., Gascon, M., De Castro Pascual, M., Basagaña, X. Morgan, I.G. & Nieuwenhuijsen, M.J. (2017).Green spaces and spectacles use in schoolchildren in Barcelona. Environmental Research, 152, 256–262 (2017). https://doi.org/10.1016/j.envres.2016.10.026

de la Iglesia, H.O., Fernández-Duque, E. … Valeggia, C.R. (2015). Access to electric light is associated with shorter sleep duration in a traditionally hunter-gatherer community. Journal of Biological Rhythms, 30(4), 342-350. https://doi.org/10.1177/0748730415590702

Downey, K. (2023, April 17).  No window in your bedroom? It could be the future of low-cost housing in Honolulu. Honolulu Civil Beat. https://www.civilbeat.org/2023/04/no-window-in-your-bedroom-it-could-be-the-future-of-low-cost-housing-in-honolulu/

Fishbein, A.B., Knutson, K.l. & Zee, P.C. (2021). Circadian disruption and human health. Journal of Clinical Investigation, 131(19), e148286. https://doi.org/10.1172/JCI148286

Frumpkin, H., Bratman, G.N., Breslow, S.J., Cochran, B. … Wood, S.A. (2017). Nature contact and human health: a research agenda. Environmental Health Perspectives, 125(7). https://doi.org/10.1289%2FEHP1663

Heschong, L., Wright, R.L. & Okura, S. (2002). Daylighting Impacts on Human Performance in School. Journal of the Illuminating Engineering Society, 31(2), 101-114. https://doi.org/10.1080/00994480.2002.10748396

Heschong, L. et al. (2003A). Reanalysis Report. California Energy Commission, PIER Program, report 500-03-082-A-3.

Heschong, L. et al. (2003B). Windows and Classrooms. California Energy Commission, PIER Program, report 500-03-082-A-7.

Heschong, L. (2001, November 18). Why fake windows are a bad idea.  Blog .https://www.lheschong.com/post/why-fake-windows-for-dorms-are-a-bad-idea

Houser, K., Heschong, L. & Lang, R. (2022). Buildings, lighting and the myopia epidemic. Leukos, 19(1), 1-3. https://doi.org/10.1080/15502724.2022.2141503

Hu, J., Shi, Y., Zhang, J., … Xue, T. (2022). Melanopsin retinal glanglion cells mediate light-promoted brain development., Cell, 185(17), 3124-3137.  https://doi.org/10.1016/j.cell.2022.07.009

IES. (2023). ANSI/IES RP-46-23supporting the physiological and behavioral effects of lighting in interior daytime environments. Illuminating Engineering Society.

Kompier, M.E., Smolders, K.C.H.J., Kramer, R.P., van Marken Lichtenbelt, W.D. & de Kort, Y.A.W. (2022). Contrasting dynamic light scenarios in an operational office: Effects on visual experience, alertness, cognitive performance and sleep. Building and Environment, 212, 108844.  https://doi.org/10.1016/j.buildenv.2022.108844

Moreno C.R.C, Vasconcelos, S., Marqueze, E.C, Lowden, A., Middleton, B., Fischer, F.M. Louzada, F.M. & Skene, D.J. (2015).  Sleep patterns in Amazon rubber tappers with and without electric light at home. Scientific Reports, 5, 14074.  https://doi.org/10.1038/srep14074

Niland, J. (2023, November 29). UCSB megadorm designer Charles Munger passes away at 99. Architect News.  https://archinect.com/news/article/150404055/ucsb-megadorm-designer-charles-munger-passes-away-at-99

Relman, E. (2023, March 25). Sunlight in your bedroom could become a luxury as cities debate allowing landlords to rent windowless rooms in former office buildings to alleviate the housing crisis. Business Insider.

Safranek, S., Collier, J.M., Wilkerson, A. & Davis, R.G. (2020). Energy impact of human health and wellness lighting recommendations for office and classroom applications. Energy & Buildings, 226, 110365. https://doi.org/10.1016/j.enbuild.2020.110365

Smolenski, M.H., Portaluppi, F., Manfredini, R., … Haus, E.L. (2015). Diurnal and twenty-four hour patterning of human diseases. Sleep Medicine Reviews, 21, 12-22.  https://doi.org/10.1016/j.smrv.2014.06.005

Stothard, E.R., McHill, A.W., Depner, C.M., … Wright, K.P. (2017). Circadian entrainment to the natural light-dark cycle across seasons and the weekend. Current Biology, 27(4), 508-513. https://doi.org/10.1016/j.cub.2016.12.041

Ulset, V., Vitaro, F., Brendgen, M. Bekkhus, M. & Borge, A.I.H. (2017). Time spent outdoors during preschool: Links with children’s cognitive and behavioral development. Journal of Environmental Psychology, 52, 69-80. https://doi.org/10.1016/j.jenvp.2017.05.007

Wirz-Justice, A., Skene, D. & Munch, M. (2020). The relevance of daylight for humans. Journal of Biochemical Pharmacology, 191, 114304. https://doi.org/10.1016/j.bcp.2020.114304

Wright, K.P., McHill, A.W., Birks, B.R.,  … Chinoy, E.D. (2013). Entrainment of the human circadian clock to the natural light-dark cycle. Current Biology, 23(16), 1554-1558. https://doi.org/10.1016/j.cub.2013.06.039

Yang, Y., Chen, W., Xu, A., … Lin, H. (2021). Spatial technology assessment of green space exposure and myopia. Ophthalology, 129(1), 113-117. https://doi.org/10.1016/j.ophtha.2021.07.031

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