Unwanted, 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.