An important group of recent studies is validating the green building requirement that access to daylight be increased. These studies deal with benefits connected to, but separate from, outcomes related to energy efficiency strategies. While they do much for establishing the health and productivity benefits of green building, they also raise the need for a clear understanding of those benefits through evidence-based design—and for caution when designing to support some of the same outcomes.

Studies of academic institutions and retail stores, and from medical and healthcare outcomes investigations, are beginning to link exposure to sunlight and/or daylight and outdoor views through a building's windows to increases in student performance and retail sales1 and decreases in recuperation times for patients hospitalized for certain conditions. While the reasons for some of these outcomes are known, others are still conjectural. It is apparent, however, that the economic utility and health benefit of daylight per se needs to be actively pursued—with context-specific care.

Creating Access to Daylight

First and foremost, energy conserving buildings try to increase their performance through optimizing (when possible) a building's orientation to north/south daylight and attempting to control heat gain through shading devices and highly insulating wall assemblies. Design strategies to create optimal access to daylight may include using larger windows, skylights, and roof monitors, which will reduce the need for lighting and other associated energy costs. However, reasonably designed walls can have six times more insulating value than the best thermal glass. So the best strategy often has tended to be striking a balance between building energy conservation, the value of occupant performance or outcome, and the marketing value of buildings with more glass.

As an example, in comparisons of old and new public schools in California, Colorado, North Carolina, and Washington, students in classrooms of new buildings with more daylight (i.e., increases of up to 30% in total window area) performed better on math and reading tests.2 The new buildings reportedly also stayed within budget projections.

Sunlight and Patient Recovery

The association between sunlight and patient recovery time is emerging tentatively as an important factor in healthcare design. In a study of more than 600 patients admitted for myocardial infarction, those who stayed in sunlit rooms had a stay of 2.3 days versus 3.3 days for those who stayed in nonsunlit rooms. The mortality rate was also higher for patients in nonsunlit rooms.3 Patients recuperating from spinal surgery in a Pennsylvania hospital were assigned to single rooms in different parts of the hospital that were categorized in terms of sunlight exposure (bright or dim). A questionnaire was administered a day after surgery and before discharge. Those patients who occupied the bright, sunlit rooms experienced less perceived stress and a greater reduction in pain, using 22% less analgesic medication per hour compared with those in dim rooms.4 Although not dealing with daylight directly, a study of surgical patients assigned to rooms with windows looking out on a natural scene had shorter postoperative hospital stays and took fewer analgesics compared with people not in these rooms.5

In somewhat parallel studies dealing with the treatment of seasonal affective disorder, a type of depression that afflicts an estimated 6.5% of the adult population, a direct connection has been established between morning bright-light therapy, as a substitute for exposure to daylight, and a reduction of symptoms. In another type of artificial light therapy application, it was found that morning light therapy decreases the occurrence of antepartum depression during pregnancy.6 The study also suggested that light therapy might reduce postpartum depression.

Bridging the gap between the value of daylight and artificial bright light for patients with depression, a study suggests that those whose sleep patterns allowed them to rise earlier rather than later in the morning were less depressed.7 However, investigations are now beginning to more clearly define the benefits of sunlight and/or daylight to patients with depression.8,9 In one study, patients admitted to a hospital for nonseasonal bipolar depression were assigned to east- or west-facing rooms. Patients occupying the east-facing rooms, which received morning sunlight, stayed an average of 3.67 days fewer than patients in the west-facing rooms.10 Similarly, in another report, depressed patients admitted to an inpatient psychiatric ward who were assigned sunny rooms had an average stay of 16.9 days compared with 19.5 days for those in dim rooms.11

Complicating matters, the benefits and risks of sunlight are becoming more evident through emerging ecologic and epidemiologic studies. This is where designers who seek to use sunlight directly in their building design strategies should be careful.

Daylight and Cancer Mortality

Once outside the context of daylight in the built environment and into the realm of daylight alone, studies are using demographic and health data to explore the association between daylight and select cancer mortality. One study found that those who lived in geographic areas with higher amounts of seasonal sunlight tended to die less frequently of select cancers than those in geographic areas with less daylight.12 In another study, a relationship was established between women who had long-term workplace and residential exposures to daylight: In that case, increased daylight exposure time was associated with decreases in breast and colon cancer.13

Conversely, studies of nurses showed an increase in the occurrence of select cancers as a possible result of working for many years on night shifts in which exposure to artificial light occurred during their biologic circadian evening time.14, 15

Overexposure to daylight has an entirely different outcome. In 2002, one million new cases of skin cancer were reported in the United States, or one case for every 285 people. Skin cancer, in general, is increasing at a rate of 4 to 6% annually, and a relationship has been established between the worldwide incidence of skin cancer and exposure to ultraviolet radiation (UVR) in sunlight.

Efforts to define how much exposure to sunshine (as UVR) might be beneficial or harmful are just beginning and are at a descriptive phase. For example, it has been estimated that, countrywide, adults who work outdoors receive approximately 10% of available UVR while adults who work indoors and children receive about 2 to 4%.16 Somewhere within these exposure times, detrimental effects occur, such as sunburn, photoaging, eye damage, and DNA damage.

However, certain cultural values regard sunshine and tanning as positive, and therefore warnings against overexposure to UVR are often not heeded.17 But UVR is biologically beneficial at some level of intensity or exposure time for health maintenance. Explanations of this benefit stress the different roles of serotonin and melatonin, the body's circadian rhythm response to light, and the role vitamin D, which is formed naturally in the body as a result of UVR, has in bone maintenance and, potentially, as a deterrent to certain cancers.

Taken together, these studies begin to reinforce the importance that daylighting interior spaces has in not only reducing the need for energy and lighting, but in maintaining work productivity and increasing the healing capabilities of medical facilities.

Size Isn't an Issue

An article in Environmental Building News recently stated that healthcare facilities could be seen as another building type that could benefit from green building strategies. But the article also stated that healthcare facilities tended to stand apart from most green buildings because of their larger than average size of 168,000 square feet (when compared with commercial buildings) and are therefore not representative of the issues being addressed in green commercial buildings.18

The positive, large green building experiences that are occurring in New York City strongly suggest otherwise. The Condé Nast Building (1.6 million square feet), the Hearst Tower (850,000 square feet), the New York Times Tower (1.54 million square feet), and the Bank of America Tower (2.2 million square feet) total more than 6 million square feet of green commercial space. Add to that total the three green residential towers at Battery Park City averaging at least 350,000 square feet each now occupied, as well as four other sister green residential buildings of similar size presently being designed.

Size is not an issue in valuing green building strategies and their outcome. Whether those green strategies support ecologic issues, resource conservation, or low-impact technologic approaches, all the strategies are eventually focused on health, welfare, and quality of life. The real difficulty lies with the fact that green building, to date, is heavy on energy conservation as the prime validated benefit and light on evidence-based design once it moves beyond energy paybacks.

The question for healthcare design may be: What building-related problems do healthcare providers perceive as important? In a recent review of selected research related to the physical environment of hospitals by The Center for Health Design,19 32% of the papers reviewed (by informal assessment) were concerned with identifying and attempting to control hospital infections and pathogen vectors; 20% were concerned with the impact of noise on necessary healthcare delivery functions and patient recuperation; 12% involved the benefits of light, views, or gardens; and 11% dealt with a variety of human factor issues, accidents involving patients, and wayfinding.

It would seem that there is ample opportunity for healthcare professionals who have a functioning research methodology at their fingertips to start extending the scope of those investigative tools into the costs of illness and the benefits of various treatments. They could then start delving further into the realm of what portions of materials, resources, and energy are represented in those costs and benefits. The outcome might result in a surprising contribution to the green building state of the art. HD

Asher Derman, PhD, is President of Green October, LLC, an independent environmental consulting firm located in Elizabeth, N.J. For more information, visit


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