The BRE has published some fascinating insights into the positive effects of daylighting in healthcare establishments on its ‘Designing Buildings Wiki. The following are edited excerpts from this report:

The issues associated with SBS (Sick Building Syndrome) and/or daylight deprivation, coupled with a renewed interest in the use of daylight in the design of low-energy, sustainable buildings is leading many architects and engineers to consider innovative ways of exploiting the benefits of daylight (and views from windows) without the negative impacts associated with solar over-heating. However, there are concerns that current health implications associated with excessive solar exposure (e.g. skin cancer etc.) could inhibit the re-emergence of a renewed interest in solar architecture. It is critically important that the positive benefits of daylight do not become confused with the negative impacts associated with excessive so

lar radiation, not least because modern glazing can reduce the transmission UVs.

Compelling, objective, independent research evidence regarding human health associated with daylight in the healthcare sector is presented in this report.

Impact of daylight on average length of in-patient stay

A number of peer-reviewed independent studies provide evidence that access to daylight enables patients to be discharged from hospital sooner than patients without daylight access.

A study by Choi et al, published in 2012, found that;

‘A significant relationship appears to exist between indoor daylight environments and a patient’s average length of stay (ALOS) in a hospital. 25% of the comparison sets showed that, in the brighter orientations, as in rooms located in the SE area, the ALOS by patients was shorter than th

at in the NW area by 16%-41%. Further, no dataset showed a shorter patient ALOS in the NW area than in the SE.’

Post-operative recovery

A literature review of the effects of natural light on building occupants undertaken by Edwards and Torcellini states;

‘Improving the mental well-being of patients improves their recovery rates. Recent studies show that daylit post-surgical facilities improve this mental well-being. Intensive Care Unit (ICU) areas in hospitals can be very stressful for patients and workers. Some patients can develo

p “post-operative delirium” in a stressful environment, which affects the intellectual ability of the patient. Many factors affect the development of the delirium: age, alcoholism, drug abuse, sex, preoperative anxiety, sleep deprivation, and perceptual distortion). Daylight helps reduce the stress associated with this environment’.

Daylight and pain relief 

Research has demonstrated a clear link between daylight/sunlight and a reduced requirement for pain relief medication in hospitals. The use of analgesic medication can result in side-effects and for this reason any strategy which reduces the requirement for pain-relief medication is desirable.

A study published in the Journal of Psychosomatic Medicine in 1995 concluded;

‘Consecutive patients undergoing elective spinal surgery who were assigned postoperatively to rooms on either the bright or dim side of the hospital unit. The patients staying on the bright side received 46% more natural sunlight and required 22% less opioid equivalent analgesic medications during their hospitalization. The patients staying on the bright side also experienced a 21% reduction in analgesic medication cost compared with patients on the dim side.’

Sunlight –nature’s disinfectant

Experiments undertaken in the USA and the UK between 1941 and 1944 demonstrated the extraordinary and remarkable effectiveness of daylight in killing the bacteria streptococci (32). The blue light in skylight was found to be particularly potent. The trials also examined the bactericidal effects of artificial light, which was found to have little value as a disinfecting agent.

Even diffuse daylight passing through two layers of glass from a north window was found to be highly effective in killing haemolytic streptococci within 13 days, with the same strain surviving in the dark, at room temperature, for 195 days.


The majority of peer-reviewed research associated with the benefits of daylight has been undertaken in healthcare and educational buildings, where the body of evidence is clear and compelling. Research has also been undertaken associated the workplace and in retail buildings which confirm the findings from healthcare and educational establishments.

The key findings have demonstrated that in healthcare, access to daylight provides; a reduction in the average length of hospital stay, quicker post-operative recovery, reduced requirements for pain relief, quicker recovery from depressive illness and disinfectant qualities. There is also a growing body of evidence that daylight plays a critically important role in the prevention and treatment of obesity, heart disease and other illnesses exacerbated by stress.

For detailed information and reference to sources, read the full report at: at