The CDC reports that six in ten Americans suffer from a chronic disease, and many suffer from two or more conditions. A growing body of evidence shows that repeated disruption to the circadian system — the rhythms that regulate the timing of the biological systems in the human body — lays the foundation for the development of chronic diseases. For example, researchers have linked chronic circadian and sleep disruption to metabolic disease, cardiovascular diseases, cognitive disease and cancer.
The circadian system is aligned to the 24-hour day through external cues, namely light exposure and timing of eating. In the U.S., people spend on average about 90% of their day indoors. While architects and employers can’t control when people eat, we can and do control people’s light exposure. Light exposure in the workplace, healthcare environments and schools, where people typically spend a third of their day, has a profound influence on the overall wellness for individuals and communities. Troublingly, research has also shown that conventional light levels in buildings and architecture in design are too low to adequately entrain the circadian system, creating environments that undermine human health.
To Create Healthier Buildings, Rethink Lighting
As the world rebounds from the Covid-19 crisis, now is the time to reconsider how to approach lighting in buildings. Here are some key guidelines to consider:
1. Lighting in the workplace matters. Research has shown that providing a high light level earlier in the day can improve sleep, but also increase resiliency to light exposure at night. The lighting environment of workplaces has a profound impact on people’s circadian systems. Designing buildings to increase daylight availability and lighting systems by providing a biologically active, high light level in the early part of the day can reduce the impact of light exposure at night and stabilize people’s circadian system health.
2. Go beyond conventional standards. Traditional lighting guidelines are based on industry standards (the Illuminating Engineering Society in the U.S.), which set light levels needed to adequately perform a visual task. Yet following these conventional guidelines is insufficient for the circadian system. Light levels generally need to be 1.25 to 2 times higher to be biologically active for the circadian system than the typical office standard. Instead, use circadian centric metrics, such as the Circadian Stimulus model developed by the Lighting Research Center, to analyze daylighting. Furthermore, incorporate lighting systems that set targets to a more biologically effective light level.
3. Start with daylight. It is feasible to incorporate additional electrical lighting loads to provide more light, but this can increase energy use and potentially counter sustainability efforts. Instead, it’s essential to first increase the amount of daylight delivered into buildings. This is no small task. The challenge is to find ways to do this without sacrificing energy performance — an imperative to mitigate climate change — or increasing visual glare. One strategy to maximize daylight availability is to evaluate different building forms and orientations for circadian-effective daylight availability in the early design stages of a project. In addition, incorporate passive shading and glazing systems to increase daylight delivery by reducing glare and heating loads, and therefore the amount of time daylight is blocked by blinds.
4. Prioritize where to supplement electric lighting. To get the most value and save resources, be strategic on where to implement electric lighting supplementation for the circadian system. Target the spaces where people spend the most time, especially in the early part of the day. If budgets are tight, consider carving out a few key zones that are light-rich, so people can work in those areas when they want. In the workspace, circadian table lamps can also provide a high-impact, low-energy solution, so long as they are accepted and used by employees.
5. A color shifting system is nice, but not necessary. While color shifting can have a positive psychological effect of simulating the passage of time, research shows that shifting to a cooler white light can actually reduce the biological effect on the circadian system through something called the subadditivity effect. Counter to traditional thinking and marketing, spaces may need to add more light to overcome this deficiency with a cooler white light, which can further increase energy loads. To decrease energy use and be just as, if not more, effective from a biological perspective, implement a simpler, cost-effective approach. For example, use static white light with a simple control system to increase light levels in the morning and reduce them in the late afternoon.
The circadian system, health and light are intrinsically linked. Access to daylight in the workplace, healthcare environments, schools, homes and other indoor spaces is not just a nice-to-have, but an imperative to human wellness and creativity. By taking a science-based circadian lighting approach, building owners, tenants, architects and lighting designers can strengthen society’s resilience to circadian disruption. Combined, the above strategies can improve the health of communities around the world and simultaneously combat the chronic disease and climate change crises.
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