Improving Your School – Part III: The Importance of Lighting
by David Epstein, October 7, 2015
Every person has a 24-hour biological cycle, or circadian rhythm, which affects our sleep patterns and our alert times. Research has shown that exposure to light, both artificial and natural, plays a major role in these cycles by stimulating the production of melatonin, a natural hormone, in the body. Higher levels of melatonin help us sleep. The timing and duration of the exposure is key to controlling the levels of melatonin in our bodies. For example, exposure to natural light after waking and darkness before bed seem to stimulate the levels of melatonin conducive for a good night’s sleep (other issues not withstanding!). During the teen age years, there is a shift in a child’s circadian rhythm, which is why so many high schools have shifted their start times to a later hour.
This is all to say that we have deep biological needs for natural light – and it affects our ability to sleep, to be alert – to learn. In fact, a landmark study by the Heschong Mahone Group in 1999 clearly demonstrated that students learn better in classrooms that had access to natural light.
Given the importance of natural light, what are the options in a room without windows? There are really four options to consider: roof monitors, skylights, solar tubes and borrowed lites. A roof monitor is a site built box with windows on one or more of the sides. This is the most effective (and most expensive) daylighting solution in that it allows for a high level of control of the light source and heat gain. It is the most expensive because their large size, custom construction, and need to do structural work to create the roof opening. Skylights, while less expensive, offer less control over light quality and heat gain.
Solar tubes are small-domed skylights connected to reflective tubes that direct sun light to a diffuser, often located in the ceiling plane. Because they are small, they can be sized to fit between structural elements and therefore require minimal structural work to install. As a result, they are often far less expensive than a skylight. The reflective tube allows the light to be directed laterally or vertically down a full story. However, because the actual dome is remote from the lens, there are no views to the sky, and the light, being diffuse, has a different feel than natural sunlight. There is still can be a feeling of being connected to the natural world, as lighting levels change based on exterior conditions.
The least expensive option is to install glass in an interior wall bordering a space that gets natural light. These are often installed in the upper section of wall to prevent disrupting views to and from the neighboring space. Often just having a view into another space helps alleviate the claustrophobic feeling of a window less space.
Ideally, the artificial and natural daylighting systems are integrated such that the room lights automatically dim when the sun is shining bright. This can be done manually too if the room lights are on multiple circuits.
With both kinds of lighting systems, the quality of the light is of paramount importance to student learning, the ultimate goal being even, low glare lighting at the work surface. This goal has been made more challenging with integration of technology. The reflection of a light source in a glass computer screen results in pupil dilation which reduces contrast and causes eye strain. Glare can be reduced by using light fixtures which bounce the light off of other surfaces (indirect lighting) or by selecting fixtures with diffusers that screen the light source.
Because investments in lighting upgrades often have the quickest return on investment (ROI) of any energy efficiency improvement in a school, and there are often incentives, a thoughtful lighting approach can save money as well as boost wellness and learning.