Exposure to adequate levels of sunlight is critical for health and well-being, for physiological, psychological, and neurological reasons. Proximity to windows, outdoor views (ideally some nature), and daylight is paramount. Buildings should utilize daylight as a primary source of lighting to the greatest extent possible. 75% of an indoor space that is regularly occupied should ideally be within 25 feet of view windows. At least 55% of regularly occupied spaces should receive 28 footcandles of daylight for at least 50% of the time the space is occupied during the day. However no more than 10% of the space should receive more than 93 footcandles. Ideal lighting involves proper exposure to diffuse daylight as well as careful design of windows to avoid excessive glare and heat gain. Balancing energy performance, thermal comfort, and access to quality daylight are essential to proper building design.

In addition to facilitating our vision, light influences us in non-visual ways. We have internal clocks that synchronize physiological functions on roughly a 24-hour cycled call the circadian rhythm. Light is the most important cue that keeps our internal clocks synchronized. Light enters our eyes and hits photoreceptors on the retina which are critical to the circadian system, sending information to various parts of the brain to trigger reactions downstream in the body. They tell the brain what time of day it is based on the light received and this main clock then synchronizes clocks in the peripheral tissues and organs. Multiple physiological processes – including those relating to alertness, digestion, and sleep – are regulated in part by the hormones involved in this cycle. Light greatly affects the quality of our sleep. 50 to 70 million American adults have a chronic sleep disorder. Such disorders and sleep deprivation are associated with diabetes, obesity, depression, heart attaches, hypertension, stroke, and other illnesses.

All light, not just sunlight, affects our internal clock. Since we spend so much time indoors, artificial lighting has a huge impact on our circadian rhythm. To maintain our internal clock optimally, we need periods of both brightness and darkness at the right times. However, our need for adequate light levels to perform activities such as reading, eating, and other tasks must be balanced with the right lighting that keeps our internal clock on time. Being in bright light during the first part of the day, and lower and lower light levels in the latter part of the day is important. If that is challenging, there are now lighting products on the market that change intensity and color throughout the day to keep our internal clock synchronized. It is important to control glare while in bright light to avoid eye discomfort, fatigue and visual impairment. Glare from windows can be controlled with adjustable window coverings, external shading systems, or other strategies. To prevent glare from artificial lighting, the lighting should be diffused or indirect. Staying away from artificial blue-ish light that mimics daylight after the sun sets is key. Certain light bulbs, computer screens, phones, and TV screens emit blue-ish light.

The light level in a space contributes to the perception of spaciousness and overall appeal of a space. Task lighting is a good way to provide enough light for tasks without over-illuminating an entire space. Using adjustable task lighting along with indirect or diffuse general lighting is ideal. There should not be a huge contrast in brightness levels between rooms and corridors or task surfaces and adjacent surfaces, so that eyes don’t get stressed when moving from room to room. Brightness levels should be distributed fairly evenly across ceilings to avoid dark spots and glare spots.

Light reflecting off glossy surfaces can also cause indirect glare which is uncomfortable for our eyes. Its important to position computer screens, desks, reading chairs, and dining or activity tables that are near windows or directly under lights to minimize glare. Light color in addition to brightness level is important. Color impacts the appeal of space and can either contribute or detract from our eye comfort. Poor color quality can make objects difficult to see correctly. Foods, skin, and plants may appear dull or non-appetizing.

Since most light within buildings is reflective, the quality of surfaces important. Surfaces can either absorb light or reflect it. To increase overall room brightness, utilizing reflective surfaces that are not too glossy and create glare is best.

Lastly, outdoor space should be provided so that building occupants can soak up some direct sunlight and vitamin D which is crucial for good health. Ideally, the outdoor space should be in a nice setting that promotes it’s use.

Lighting is just one of several crucial factors for wellness, although it's one that interior designers and architects can most easily affect. See our other articles on how property and business owners can provide good quality air, water, nutrition, fitness opportunities, comfort, and promote good mental health.