Glaring Light Equals Light Trespass
Drive down any road in the area in the early evening and notice how
many lights look like the picture below.
I will call these barn lights in what follows. The typical fixture is a 175-watt Mercury Vapor lamp. Including the ballast the actual power
rating comes closer to 210 watts.
These fixtures were designed in the 1960's with little regard for
efficiency, aesthetics, or good light usage. Fully 47% of the light from the barn light is directed
upward. Most use a photocell in order to operate between dusk and dawn. Using average cost factors for power, a
single barn light costs about $70 per year in electricity over and above the
monthly charge from the utility company.
In the USA it is estimated that $700 million per year is spent on this
one light fixture. With a waste
factor of 47%, that's $329 million per year thrown away. To produce the wasted energy requires
about 11 million barrels of oil.
Many in the lighting industry refer to the barn light as a
"glare bomb" and rightly so.
The aim is to throw as much light around as possible, with little regard
for where it goes. We don't expect
our neighbors to erect security fences on our property. We don't want the neighbor's attack dog
in our yard. But over the last
thirty years we have permitted the unwanted intrusion of light on our property
from a neighbor's misdirected, glaring, and overpowered security light. This is referred to as "light trespass."
The solution can take several forms. The shield of the fixture can be easily removed and replaced
with the Hubbell Sky Cap. The cap
captures the upwardly directed light and projects it downward. With more light now going to where it
is needed, a lamp of lesser wattage can produce the same illumination. The industry standard is to replace the
175-watt mercury lamp with the 50-watt high-pressure sodium lamp to achieve the
same level of surface illumination.
Simple timer circuits are available so that the fixture can be turned
off after (say) midnight. Even
more effective are motion sensors that turn the light on when nearby motion is
detected. The surprise to the
intruder is much more effective that providing a light for his activities. The City of Nacogdoches already has a
lighting ordinance that prohibits light trespass. If you are interested in the efficient use of outdoor
lighting, contact me at 468-3001.