U.S. Department of Energy - Energy Efficiency and Renewable Energy
Building Technologies Office
Hospital Energy Alliance: Daylighting Video (Text Version)
Below is a text version of the Hospital Energy Alliance video showing the importance of daylighting to hospital energy efficiency, staff performance and retention, and patient healing.
Daylighting brings natural light into hospitals to reduce the use of electric lighting. Daylighting has also been shown to aid in patient healing, to improve the work environment of staff, and to enhance the well-being of patient families.
Daylighting is using the sun to offset electric lighting. And so there is a huge potential for energy savings there because you're using the glass to help provide some function in the building other than just views. You're actually using it for energy savings.
We can almost eliminate cooling in probably 50 percent of the hospital just by reducing the loads: reducing the solar gains, controlling the light, and being very careful with equipment. These systems all lead us back to quality-of-light issues, the role of light in reducing cooling loads, which actually is a large energy consumer, but is a key component in capital costs.
When you look at the energy use in a hospital, the electric lighting loads can tabulate almost 30 percent of the entire electric bill, so if you want to look at saving energy, that's one of the largest chunks.
Most buildings have windows; therefore, there's opportunity for daylighting. We can get more of an advantage by designing those windows to really improve the lighting quality in the space and get the electric lights off.
We're involved a lot with Better Bricks. They are the Commercial Buildings Initiative for the Northwest Energy Efficiency Alliance. When this Legacy project started, they offered to help out and do a daylighting study of parts of the hospital and we did two studies, one specifically for the patient rooms and one for the public areas. And they came back to us with nine strategies for designing the exterior wall of the patient rooms to maximize the amount of daylighting that we could get and the study was fantastic, 'cause it showed that they could save almost $6,500 a year in electricity savings just by utilizing some of these strategies alone. I think the biggest strategy we used was separating out the daylighting window from the view window.
We like to have windows to be able to get the visual relief of seeing outside—a little bit of a relief to our system, a little bit of relief to our eye; certainly the relief of chronic stress in the workplace, but we also need to think about the quality of light.
To get the light into the patient room, you only need the top portion of the window, which is above six feet to the underside of the ceiling. You can see that we've divided the patient room window up into to the daylighting window and the view window, so the daylighting window glazing specification allows more light into the room and the view window has a higher performance glass that lets less light into the window and reduces glare for the patient and the visitors.
Daylighting is also central to the energy efficiency strategy of the Dell Children's Medical Center of Central Texas.
The way we planned mechanical units, where we chose to have glass and glazing versus where we chose not to in terms of orienting it to the sun. It's a totally integrated system of technology and just good old-fashioned design. The biggest impact on the space layout was the decision to add courtyards to the building. They were originally driven by the desire to get daylighting.
The building has four different types of windows in it, depending on whether they are facing north, south, east or west. We did computer models of what the ambient exterior light would look like from dawn to dusk, seven days a week, all four seasons of the year and arranged the lighting system in the building to accommodate that, so that we can save energy.
Scientific studies have shown that the exterior views that can accompany daylighting have a profound impact on patient healing.
All life, including human life, was evolved under a sunrise and sunset, and the spectrum of that was natural blue light coming in the morning and sunset with no blue light and only some red and orange in the evening. Our genes were all developed for that. You need to have the proper lighting in the morning for the alertness because that makes serotonin, dopamine, and cortisol, and that turns on the immune system that gets rid of infections, that gets rid of bacteria, that helps fight viruses. But at night, if you have the blue light, you're interfering with the immune system by interfering with the production of melatonin, and that isn't just a sleep hormone; it also affects the immune response to prevent cancer.
Access to light is also critical to hospital workers, a fact that affects the bottom line at health care facilities because of the importance of employee retention and the high cost of replacing key staff.
In critical task spaces, we're really concerned about, one: they get view, but two: the quality of light is one that doesn't provide a lot of glare and provides at least a minimum level of illumination for ambient tasks within a space, which usually means diffuse light.
We've realized in the last 10 years that our eyes are more than just for vision. They also capture daylight on a physiological level through a photo-biological receptor that captures light; light during the day and it's just as important for these hormonal cascades to have dark at night. This has a big implication in our health care environments. For the staff who potentially will go in in the morning in the dark, come home at night in the dark—12-hour shifts with no light during the day. So that has ramifications on our built environment in the hospital setting to create spaces for staff that allow daylight into their work areas.
My favorite thing about this facility is that you can't be farther than, I don't know what the exact number is, but 30-40 feet from an open courtyard or light streaming in.
If the staff is working at night, they are going to suffer from certain shift-work problems. But if you can have natural lighting during the day, and the natural darkness in the evening, then when they go home, they'll be able to sleep.
Daylighting, part of a comprehensive energy strategy that benefits patients, staff, and the bottom line of today's hospitals.