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See the light

The smart use of natural illumination supports the health and happiness of patients, employees and clients. Artificial light has its place, too, but you should be selective.

See the light
A skylight grid introduces natural daylight to multiple workstations. LED strip fixtures were installed to produce indirect uplighting. Task exam lights are present at each treatment station.

What if I told you about a simple strategy that would make team members feel more alert, improve their attitude and attendance, and help them achieve higher goals? It also would help clients feel more relaxed and, most importantly, reduce patient stress. When implemented during a hospital’s construction or renovation, it would cost very little and save money over the building’s lifetime.

What is this magic? It’s natural light.

Multiple studies have proven the health and mental well-being benefits of sunlight. Of course, uncontrolled sunlight can be harsh and stress an air conditioning system, so the trick is in knowing how and where to use natural light.

How Light Affects Health

A previous article of mine — “Make Your Hospital a Comfort Zone” — discussed the concept of healthful spaces. Intuitively, we sense when a space makes us feel better or worse. Have you ever seen rows of office cubicles lit by flickering, yellowish fluorescent fixtures? Sure, the layout is an inexpensive way to pack in more workers, but what of their productivity? What of their absenteeism and mental health? If your goal is, as it should be, to create a workplace that enhances your life and those of your staff, clients and patients, then a more thoughtful approach is needed.

Evidence-based design is the idea that the benefits of design choices can be measured by

comparing outcomes. Research into human health care has found that a patient exposed to a pleasing exterior view, including green space, and who maintains a natural night-day circadian rhythm will recover faster than one closed off from the outside world. “ICU psychosis” is real, and solid evidence exists that animals react in a similar way.

When used in ICUs and wards, natural light will reinforce the natural sleep-wake cycle. Morning light has a higher energy blue-white cast, so it triggers the brain into higher awareness. Normal daytime light has a more neutral color. Evening light has warmer tones, tending toward the red end of the spectrum and triggering melatonin production.

If you are interested in creating a healthful space, you must consider the patient, client and staff because one plays off the other. Veterinary patients can be anxious and even fearful of a clinic. Why? We often say it’s because they pick up on other fearful animals. Surprisingly, it might be because of their owners.

A study published in 2017 in Animal Cognition — http://bit.ly/2wvkKWw — established a link between the stress of a person and that of dogs through chemosignals alone. Add to that a dog’s well-

documented ability to read facial expressions and body language and we see that client comfort greatly affects patient comfort. Make your clients happy and their pets likely will be happy, too.

Capture Natural Light

In general, we want to see sunlight but not be directly exposed to it. Light from the south and west can be harsh and make us uncomfortably hot, even with the A/C blasting. Instead, we want northern and cool morning eastern light.

Southern light can be easily controlled using exterior overhangs. With western light, aggressive and costly architectural approaches are necessary, so we tend to limit the glass on that side of a hospital.

Skylights and light tubes are great for illuminating interior spaces. Light tubes are similar to skylights in that they are roof-mounted, but they are less expensive, easier to waterproof and do better at distributing light across a wide area. The light is reflected rather than direct, so the interior stays cooler.

Borrowed light, on the other hand, is the use of interior windows to carry light into interior rooms. We all know how exam rooms can feel small and tight, but improvements such as transoms over doors, high and wide clerestory windows, and full-height frosted glass will transform a claustrophobic room into a welcoming space.

Depending on a building’s shape, a clerestory window can be introduced to an interior room by raising the ceiling and roof. This approach works best in larger spaces like treatment rooms. Since most clinical spaces surround the treatment area, they can all benefit from borrowed light.

When to Use Artificial Light

The sun doesn’t always shine, of course, so light fixtures are necessary. Even here, much can be done to maintain a healthful environment. The first step is to select the right light source. These days, there is little reason to use anything other than LEDs. They are energy efficient at about 100 lumens per watt, they are easily and cheaply dimmable, and they do not contain toxic mercury like fluorescent lamps do.

Another advantage of LEDs is the wide range of color temperatures. The color a light renders is expressed in degrees Kelvin. Lower numbers are more warm and higher numbers are cool. A 2500K lamp is considered warm white, 3500K is cool white and 4500K is close to daylight. Anything above that will look unnaturally blue.

The standard choice in my firm is 4000K lamps. That way the light-tube diffusers and LED fixtures appear to have the same color. 4000K also gives a good color rendition index (CRI). Full daylight has a CRI of 100. A lamp with CRI 85 or above is very good and is important in clinical spaces to support accurate visualization and diagnosis.

An added benefit of high CRI light sources is that your interior design colors will render correctly, which leads us to light’s architectural uses.

Count the Advantages

Here are a few key things to realize:

  • Higher light levels will make a room appear bigger.
  • A low ceiling can be visually overcome by washing the surface with uplight, meaning a light source set in an upward direction.
  • Tall spaces will retain their impact at night when brightly illuminated. If the ceiling has a high reflectance, the entire space enjoys ambient light.
  • Conversely, if you wish to draw attention away from the ceiling, downlights will accent lower spaces and features.
  • Washing a wall with light from purpose-made fixtures will highlight logo walls and can add visual interest to otherwise unremarkable spaces.
  • Long hallways can appear less so by illuminating a side wall. A shadowed, or less bright, end wall will appear to advance.

Color Palette

As I discussed, natural light colors vary across the day. With artificial light, a similar effect can be achieved by means of light tuning. A great feature of some LED fixtures is that their color can be changed by using programmable drivers. When natural light isn’t present in ICUs and wards, the technology can be used to support the cycling of daylight. It’s also installed on the International Space Station to help astronauts keep a healthy 24-hour cycle as they circle the Earth every 90 minutes.

As we talk about light color, we must consider the surfaces being struck by light. Virtually everything we see is actually reflected light. The color and brightness that reaches our eyes is a function of both the light and the surface. This is where interior materials and color selection become important. Remember that dark-colored finishes require fixtures with a higher lumen output to achieve the same illumination levels of light colors.

As you can see in the photos, all the finishes are medium to light in color with the exception of some accent surfaces. Interior and lighting design must work hand in hand.

Constructive Criticism columnist Paul Gladysz is the principal architect at BDA Architecture. The Albuquerque, New Mexico, firm specializes in the planning, design and construction of animal care facilities.

Shaded south-facing windows and clerestories permit indirect natural light to illuminate a clinic’s lobby. A light shelf above the reception desk reflects daylight toward the upper ceiling.


North-facing windows provide ample diffuse ambient light and minimal heat gain at a Phoenix veterinary practice.


Frequency-tuned LED fixtures mimic daylight in interior spaces.


Natural light supports an animal’s circadian cycles in housing and ward areas. Bilevel and dimmable fixtures reduce night-time artificial light but permit staff monitoring.