What's Happening from Environmental Building News
January 1, 2010
Photoluminescent Exit Signs Not Energy Efficient
The National Electrical Manufacturers Association (NEMA) has released a paper examining frequent claims about photoluminescent exit signs, which glow in the dark after charging under available light (see
EBN Nov. 2006). After considering manufacturer claims about safety, energy efficiency, and total cost, NEMA concluded, as did
EBN in our 2006 article, that these signs may not be as effective as claimed, and recommends that designers carefully consider the options before specifying exit signs.
The NEMA paper finds that claims about the energy efficiency of photoluminescent exit signs may be overblown. Such claims rely on the fact that the signs themselves do not draw any power. But many codes and standards, including the International Building Code, require that the signs be illuminated at least 60 minutes prior to building occupation; manufacturers note on the signs that at least five footcandles of external light must be available to charge the sign during occupied hours. According to NEMA, these signs require light fixtures for charging that use far more than the two to five watts used by internally illuminated, LED exit signs.
Given the additional lighting needed to charge these exit signs, they will likely not be as low-maintenance and cost-effective as manufacturers claim. The NEMA paper points out that a skilled electrician is needed to install light fixtures near the signs in order to meet manufacturer specifications and code requirements. These light fixtures will also require maintenance and additional lamps over time, further limiting their cost-effectiveness.
Finally, photoluminescent signs may not be as safe as other signs. According to NEMA, the signs lose their glow at a rapid rate, decreasing 80% in intensity after just ten minutes. Further, the test method used to certify these signs asks participants to examine signs in a darkened room and note whether they are readable, and includes a five-minute period for the participants’ eyes to adjust—time that building occupants would not have in an emergency, according to NEMA.
– Allyson Wendt
For more information:
NEMA
“Photoluminescent Exit Signage—Factual Review”
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Source: NEMA
