Benefits of proper daylight lighting
Daylight is a term used for providing the primary light source in buildings; artificial lights supplemented the natural light. The benefits of daylight on the body and its impact on the building occupants for offices, schools, retail, health care, and industrial are reported in terms of psychology, physiology and economic benefits.

·         Daylight provides a better lighting environment than cool white or energy-efficient fluorescent electrical light sources because “daylight…most closely matches the visual response that, through evolution, humans have come to compare with all other light” (Franta and Anstead1994).

·         The majority of humans prefer a daylit environment because sunlight consists of a balanced spectrum of color, with its energy peaking slightly in the blue-green area of the visible spectrum (Liberman 1991).

·         According to Hathaway, et al. (1992), natural light also has the highest levels of light needed for biological functions:

·         The number one health problem in offices is eyestrain (Ott Biolight Systems, Inc.1997a).

·         The right kind of lighting can make a big difference in your vision: it can improve your reading ability, create a more noticeable difference in colors, and prevent eye strain. However, even with all of these proven benefits, many people are still using lights such as halogen and fluorescent that can be harmful to your eyes over a long period of time.

·         Light falling on the retina and being transmitted to the hypothalamus controls our circadian rhythms (Samuels 1990), which are responsible for synchronizing our internal clock to 24 hours (Light, Sight, and Photobiology 1998).

School children and teachers can benefit from integrating and managing daylight properly. Reported benefits include reduced utility costs for school districts, improved student attendance and academic performance, and a less stressful environment for students.

The following summary extracted from reference 1 provides understanding of daylight benefits.

Affects of Light on Internal Body Systems
Many functions, including the nervous system, circadian rhythms, pituitary gland, endocrine system, and the pineal gland are affected by different wavelengths of light. Light falling on the retina and being transmitted to the hypothalamus controls our circadian rhythms (Samuels 1990), which are responsible for synchronizing our internal clock to 24 hours (Light, Sight, and Photobiology 1998). Melatonin levels in the body determine a person’s activity and energy level and state of consciousness (Ott Biolight Systems 1997a)

Medical Cures from Light
By affecting the Terman, et al. (1986) claimed that improved interior lighting could alleviate the common subclinical problems in the population at large such as oversleeping, overeating, energy loss, and work disturbance. Appropriate administration of light therapy clears the symptoms within a few days. This is a remarkable achievement, considering the clinical severity, and makes us think we are close to the mechanism of pathogenesis. By comparison, antidepressant medications often take several weeks to work.

Daylighting in the Office
Occupants in daylit and full-spectrum office buildings reported an increase in general well being. Specific benefits in these types of office environments include better health, reduced absenteeism, increased productivity, financial savings, and preference of workers. Full-spectrum bright lights allow day and night workers to adjust their internal clocks or circadian cycles to match their work cycles. Improvements in productivity, a decrease in accidents, an increased level of mental performance, improvements in sleep quality, and an increase in morale among night shift workers have also been attributed to better lighting (Luo 1998).

Daylighting in Schools
School children and teachers can benefit from integrating and managing daylight properly. Reported benefits include reduced utility costs for school districts, improved student attendance and academic performance, and a less stressful environment for students.

A school with insufficient light can also reduce a student’s ability to learn due to the effect lighting has on physiology. Poor spectral light can create strain on students’ eyes, leading to a decrease in information processing and learning ability, causing higher stress levels (Liberman 1991). Dr. Walker (1998) found that stress impacts certain growth hormones. He determined that “persistent stress stunts bodily growth in children” because the activity of the growth-inhibiting hormones cortisol and ACTH increase under stress. Students in the Canadian full-spectrum fluorescent schools grew 2.1 cm more in two years (Hathaway, et al. 1992) compared to students who attended traditional fluorescent-lit schools.

Daylighting in Health Care Facilities
Reported benefits of natural light in hospitals and assisted-living communities are reduced lighting and heating costs as well as improved physiological and psychological states for both patients and staff. Studies show that daylighting can reduce the mental and physical strain of patients, doctors, and nurses. Daylighting has been so successful that hospital environments, as a part of the patient care program, now utilize it. Assisted-living communities are also integrating daylighting because it provides better light.

Daylighting Industrial Environments - Productivity and Safety
The study results showed full-spectrum fluorescent lights producing the lowest error score, whereas the high-pressure sodium discharge lamp produced the highest error score (Abdou 1997).

Conclusions
In conclusions LED lights with color temperatures in the range of 5000K to 6500K are good for interior of offices, colleges, schools, retail, health care, commercial and industrial buildings for ambient interior lighting, fluorescent retrofits 2x2, 2x4, 1x4, low bay and high bay lights.

Reference 1: “A Literature Review of the Effects of Natural Light on Building Occupants” by L. Edwards and P, Torcellini in July 2002, NREL/TP-550-30769.