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Circadian Rhythm and Lighting Design

As we continue to better understand the interactions between human health and the built environment, we must look at how our relationship between the amount of time spent indoors and the amount of natural light we receive affects our internal clock.  Traditionally, when conducting site visits and producing a lighting design for a given building, there are a few parameters that are of primary focus. These include; visibility, glare, shadows, colour rendering, safety concerns, aesthetics of lighting within the space and meeting appropriate light levels at specific surface heights.

The commonality between all of the aforementioned design parameters is that they are visual effects. To what extent does light contribute to effects that are non-visual related? Light regulates human biological function through circadian rhythm. Effects such as alertness, cognitive ability, sleep-wake cycle, melatonin production and hormone activation are all a result of circadian rhythm.

You can see the importance of circadian rhythm, specifically the alertness and cognitive ability when designing for manufacturing facilities, office buildings and schools. Hospitals and retirement homes are also places in which non-visual effects produced by light need to be considered.Special attention towards melatonin production is critical as it positively effects mood and can help with Alzheimer’s disease.

Circadian Stimulus Calculator

Circadian Stimulus Calculator

The Lighting Research Centre at Rensselaer Polytechnic Institute have been conducting studies on how to achieve these non-visual effects and how to activate circadian rhythm through light. They have proposed the Circadian Stimulus (CS) metric, which, is used to determine the spectral irradiance distribution of the light at the cornea. Their studies indicate that a CS of 0.3 or greater for a minimum of one hour in the morning helps to stimulate the circadian rhythm. The Lighting Research Centre has created CS calculator, to help aid with lighting design. Although in its infancy, the benefits of incorporating circadian stimulus into lighting design speak for itself. Human health and well being should always be paramount in design of any building system.