Light exposure strongly influences our circadian rhythms – biological processes that follow a roughly 24-hour cycle – as natural daylight varies in intensity and spectral composition throughout the day. 

These daylight variations play a critical role in instructing our bodies on how to regulate our sleep-wake cycle, hormone and neurotransmitter production, and even body temperature. 

Research has shown that exposure to natural daylight in the morning helps reset the circadian clock for daytime physiological activity, enhancing alertness, and overall productivity and performance throughout the day.² For example, a study published in Building and Environment showed that working in environments with abundant natural daylight not only improves occupant satisfaction but also helps cognitive function.³

1. The Health Benefits of Daylighting - Circadian Regulation

Access to natural light during the day can improve sleep quality.

Natural light is a powerful synchronizer of the body’s internal clock and can provide a variety of benefits.

Access to daylight throughout the day can help to suppress melatonin production – the hormone that signals sleep onset – and stimulate the production of serotonin during daytime hours, leading to a more robust and natural sleep-wake cycle. A study by Figueiro et al. (2017) found that office workers with greater exposure to natural daylight during the day reported better sleep quality at night and lower levels of depression.⁴ Further research conducted in the U.S. and South Korea (2020) revealed that exposure to a large amount of daylight in a workspace increased sleep time and efficiency, as well as quality of life.⁵

What’s more, in the healthcare sector, a study based on 15 years of medical data found that hospital patients with beds next to a window had shorter hospital stays than those with beds located by doors, potentially because they were sleeping better.⁶

Conversely, the lack of daylight experienced by shift workers has been shown to disrupt circadian rhythm and cause health problems, making thoughtful physiologically meaningful lighting design even more critical.⁷ It’s proven that by integrating daylight into the built environment, architects and designers can provide interior spaces that promote healthier sleep patterns and make a positive contribution to the physical wellbeing of building occupants in all types of buildings.

2. Enhanced Mood and Reduced Stress

Effective daylighting design has also been linked to improved mood and reduced levels of stress.

Natural daylight has been shown to increase serotonin levels, contributing to improved mood and higher overall emotional well-being. 

Since the COVID-19 pandemic and a rise in remote working, more and more people are spending much of their day at home. A study from 2022 demonstrated that the daylighting design of homes has a significant impact on subjective emotional wellbeing, with the most positive impact coming from maximizing the amount of daylight entering the home. It found that increased space between dwellings and larger, sun-facing windows also improved wellbeing. The biggest beneficiaries of natural daylight conditions in the home were women and young people.⁸

According to a recent literature review, direct sunlight in the room, determined by the window’s orientation, appears to be the most effective daylight-affecting factor for restorative effects. Sunnier and brighter environments appear to give the best results, followed by the proximity of the occupant to daylight or a sunny patch.⁹

These findings suggest that effective daylighting design not only benefits physical health but plays a significant role in mental and emotional health.

3. Increased Productivity and Cognitive Performance

In environments such as offices and educational institutions, productivity and performance are key success metrics.

Research has consistently found that natural daylight exposure, with its meaningfully dynamic nature, correlates with improved cognitive performance.

A landmark study published in the Journal of Clinical Sleep Medicine showed that workers with access to natural daylight experienced a 10–15 percent increase in productivity, attributed to enhanced concentration and reduced fatigue.¹⁰ 

Effective daylighting design has also been associated with improved memory retention and faster reaction times, making it a factor in optimizing work and learning environments.

Challenges and Future Directions

While the benefits of effective daylighting design are clear, there can be challenges.

Seasonal variations and geographic location can limit the availability of natural daylight, especially in regions with long winters or persistent cloud cover, and concerns about overheating and glare must also be addressed.

Our understanding of the relationship between natural daylight and human health is growing thanks to emerging research examining how time-dependent exposure to different wavelengths of light affect mood and cognitive performance, as well as the potential benefits of personalized lighting systems that replicate natural daytime light patterns and spectral content throughout the day to alleviate seasonal deficiencies in meaningful daylight exposure.

As this knowledge evolves, so does the potential for designing spaces that conserve energy and promote occupants' health and well-being, making a compelling case for considering daylighting strategies from the earliest design stages to ensure brighter, healthier, more productive spaces aligned with our innate biological needs. Retrofitting existing spaces with daylighting strategies also presents a valuable opportunity to enhance occupant well-being in built environments.

Many existing structures can be improved to better integrate natural daylight, thereby reaping the benefits of improved health and productivity. This approach not only maximizes the use of existing resources but also aligns with sustainable design principles by reducing the need for artificial lighting and energy consumption.

Citations:

1-Klepsis N, Nelson W, Ott W. et al. The National Human Activity Pattern Survey (NHAPS): a resource for assessing exposure to environmental pollutants. J Expo Sci Environ Epidemiol 11, 231–252 (2001). https://doi.org/10.1038/sj.jea.7500165

2-Blume C, Garbazza C, Spitschan M. Effects of light on human circadian rhythms, sleep and mood. Somnologie (Berl). 2019;23(3): 147-156. https://pubmed.ncbi.nlm.nih.gov/31534436/

3-Jamrozik A, Clements N, Hasan SS, Zhao J, Zhang R, Campanella C, Loftness V, Porter P, Ly S., Wang S, Bauer B. Access to daylight and view in an office improves cognitive performance and satisfaction and reduces eyestrain: A controlled crossover study. Building and Environment. 2019;165,106379. https://doi.org/10.1016/j.buildenv.2019.106379

4-Figueiro MG, Steverson B, Heerwagen J, et al. The impact of daytime light exposures on sleep and mood in office workers. Sleep Health. 2017;3(3):204-215. https://pubmed.ncbi.nlm.nih.gov/28526259/

5-Lee J, Boubekri M. Impact of Daylight Exposure on Health, Well-being and Sleep of Office Workers Based on Actigraphy, Surveys, and Computer Simulation. Journal of Green Building 1 September 2020; 15 (4): 19–42. https://doi.org/10.3992/jgb.15.4.19

6-Park MY, Chai CG, Lee HK, Moon H, Noh JS. The Effects of Natural Daylight on Length of Hospital Stay. Environ Health Insights. 2018;12:1178630218812817. Published 2018 Dec 3. https://pubmed.ncbi.nlm.nih.gov/30546262/

7-Nie J, Zhou T, Chen Z. et al. The effects of dynamic daylight-like light on the rhythm, cognition, and mood of irregular shift workers in closed environment. Sci Rep 11, 13059 (2021). https://doi.org/10.1038/s41598-021-92438-y

8-Morales-Bravo J, Navarrete-Hernandez P. Enlightening wellbeing in the home: The impact of natural light design on perceived happiness and sadness in residential spaces. Building and Environment. 2022;223 (109317). https://doi.org/10.1016/j.buildenv.2022.109317

9-Karaman Madan O, Chamilothori K, van Duijnhoven J, Aarts MPJ, de Kort AW. Restorative effects of daylight in indoor environments – A systematic literature review. Journal of Environmental Psychology. 2024;97(102323). https://doi.org/10.1016/j.jenvp.2024.102323

10- Boubekri M, Cheung IN, Reid KJ, Wang CH, Zee PC. Impact of windows and daylight exposure on overall health and sleep quality of office workers: a case-control pilot study. J Clin Sleep Med. 2014;10(6):603-611.  Published 2014 Jun 15. https://pubmed.ncbi.nlm.nih.gov/24932139/