Select a suitable light fixture.
Aim lights down. Do not allow light to shine above the horizon.
Shield every light so that the source of the light may not be seen from any other property.
Use the smallest amount of light needed for the task.
Turn it off when no one is using it.
View the Lighting Plan Checklist here and a Sample Lumen Compliance Workbook here.
Select A Suitable Light Fixture
We’ll start by looking at what types of light fixtures are best to implement these protocols. Acceptable lights shield the source of the light from most direct viewing angles. None of the acceptable fixtures allow any light above a horizontal line drawn through the lowest point of the illuminating elements.
Scroll through the photos at the bottom of the page for real life examples or follow the Quick Guide “ Better Lights for Better Nights” Diagram link below.
Quick Guide “ Better Lights for Better Nights” Diagram
Better Lights for Better Nights
Aim Lights Down at Installation
Aiming lights “down” does not mean to just angle the light towards the ground. The light must be positioned so as to not allow any light to be projected above a horizontal line drawn through the lowest part of the light-producing part of the fixture.
The light from a properly installed fixture should project below and out to the sides of the fixture. Do not let any light escape above the horizontal. To facilitate this requirement to aim lights down, install lights so that the fixture is above the area to be illuminated.
Lights that allow no light above the horizontal and no more than ten percent of their lumen output in the ten degrees immediately below the horizontal are called full cutoff (FCO). Using additional shielding to reduce the light projected in the ten degrees immediately below the horizontal to zero is even better for glare control.
An acceptable fixture that is mounted at an upward angle would change it into an “unacceptable” fixture. An acceptable fixture mounted up on a hill would require the addition of a shroud to keep it from becoming unacceptable.
Shield the Light Source
Full cutoff also know as fully shielded light fixtures, where no light is allowed above the horizontal and only a small amount is allowed near the horizontal, are often recommended. In many cases these full cutoff light fixtures are a good option. However, we now know that light emitted near the horizontal contributes more to sky glow than any other light. A light fixture with the light source shielded so that it cannot be seen from another property will eliminate light trespass and reduce sky glow.
To improve vision, the eye must be protected from directly viewing the light source. So, even full cutoff/fully shielded lights may need additional shielding to be installed in a manner that hides the source of the light from a normal viewing point. Shielding the light concentrates it where it’s needed and usually allows you to reduce the wattage to get the same or more light where you actually need it. In fact, a wattage reduction is usually required to keep that concentrated light from producing reflective glare and an over lighted situation. Light trespass is normally stopped when every outdoor light is shielded so that the source of the light cannot be seen from any neighboring property.
Use Less Light – That is Reduce the Lumens
First of all you’ll need to stay within the lumens cap for the property (25,000 lumens per net acre on a residential property – about 0.6 lumens per square foot of illuminated space).
Consider the way the human eye works when selecting the wattage, or more accurately the number of lumens, for a particular outdoor application. Use significantly less light than is the modern habit to enhance night vision. Remember that a very bright light will make the unlit areas seem impossibly dark.
What you can’t tell from the “Better Lights for Better Nights” handout at the Quick Guide Diagram link is the amount of light that each fixture produces. The amount of light produced is measured in lumens. Too many lumens (i.e. too bright a light) will cause light to bounce off of the surfaces it shines upon and reflect up in the sky, in the eyes of people trying to see nearby, into the habitat of nearby wildlife, etc. The light may draw in birds and insects that then won’t be able to proceed with their natural habits. So, the shape of the fixture isn’t everything. Lower the lumens (and wattage) when you switch from an unshielded fixture to a shielded fixture.
Did we just say lower the wattage? You bet. These fixtures not only cut the glare, allowing people to see better, but it reduces the costs of operating the lights. Win-win.
On or Off?
Lighting an unoccupied area may attract a person with ill intent. It’s often a waste of energy. A big plus for turning off the lights when no one is there to use them is that it allows wildlife to exist in natural darkness. Wildlife needs natural darkness, as do humans. Timers, motion detectors, and half-night photocells can help you achieve this.