Light + Health

NLB TV: Metrics Used for Humancentric Lighting

There are two important, sometimes competing, metrics regarding Humancentric Lighting: the Equivalent Melanopic Lux (EML) and Circadian Stimulus (CS). These metrics were discussed by a panel of experts convened at the National Lighting Bureau’s most recent Annual Lighting Forum.

Moderated by NLB Executive Director Randy Reid, the panel included Mark Lien, Industry Relations Manager, IES; Michael Barber, Principal, The Lighting Practice; and Craig Casey, Senior Building Science Engineer, Lutron Electronics.

The panel defined and discussed Equivalent Melanopic Lux (EML) as the light measured at eye level using weighting factors of the specific light source being used. It is a calculated value of the non-visual reception of response to light. The team discussed that EML is an initial metric and it has some value, but it only focuses on one photosensor. Since the establishment of the EML, an alternative metric, the Circadian Stimulus (CS), has been developed by the Lighting Research Center. The CS looks at the impact on the other sensors as well. The industry is currently debating which metric will be the most valuable.

The panel also discusses ethics and whether using lighting to influence the sleep-wake cycle is good or bad for society. The panel discussed that once the science establishes the impacts of light on human health, employers that don’t implement solutions may face litigation.

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Craig DiLouie


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