Most people do not realize how easy it is to reduce the negative impacts of Light Pollution on their own property.  This document will show you how to create very effective shielding for the common residential floodlight.  The common floodlight found at most homes is merely a screw-in bulb that is mounted in an outdoor light socket.  Throughout the 50 year history of this lamp, surprisingly it has never had an effective shield available.

The materials to create the shielding for these lamps is readily available from any hardware or home improvement center and the cost per shield is generally less than $5.00 US.  After making and installing this shield you will immediately notice more light reaching the ground below the floodlight.  This occurs because the shield redirects the wasted light onto the ground where you need it.  The light is not amplified by the shield, though you might think that it is when seeing the results on the ground after installation.  Illumination that would otherwise be wasted into your trees, onto your neighbor's property, and into the night sky is reclaimed to remain within your own property lines.

The tools needed to create this shield are found in nearly every home and you do not need to be overly talented with your hands either.  You will need a pair of tinsnips (preferred) and a standard flat blade screwdriver.  If you do not own a pair of tinsnips, a strong pair of sissors to cut the flat pattern will do the job, too.

Materials List

Quantity	Description	Department
1	5" diameter stainless steel hose clamp	plumbing
1	10" L. x 7" W. aluminum roof flashing (Available in 20' rolls or in sheets)	roofing / carpentry

To prepare for making the flat metal blank, trace the pattern shown below onto a piece of stiff paper or cardboard.  This step will be very helpful to help prepare for cutting the metal and it will also allow you to easily make more than one shield.  Manilla file folders work very well for this purpose.  Use this pattern as a template to trace the cut lines onto the aluminum sheet and cut it out.  Be very careful of the sharp metal edges that result when cutting the pattern.

Flat blank cutting pattern
 
Click to view image full size

After the metal blank is cut to the proper shape, sand the sharp edges lightly with some 150 grit silicon carbide sandpaper.  This deburring process will make the shield safer to handle while attaching it to the lamp.  Review the photo below to see the final shape.  Essentially, this shield is merely a cylintrical section, and it works very well to contain stray light that typically results from this type of lamp.

Components for PAR floodlight shield

Preparing for installation entails removing the lamp from the fixture so the shield may be formed to the proper arc before climbing the ladder to do this in place.  This will allow you to practice on the necessary steps before climbing the ladder to perform the final installation.

Remove the bulb from the socket first

Those who are familiar with bending metal know that all metals have a memory and wish to return to their original shape after bending.  To assure a proper fit, I use a cardboard tube that is one inch smaller in diameter to form the shield before installation.  If you purchase roof flashing in a roll rather than using flat blanks the metal will have the tendency to roll up on the edges.  This makes installing and forming the shield easier than when beginning with a flat piece of metal.

Installing the shield after shaping curve

After installing the shield and tightening the clamp to hold it in place you must verify the aiming angle of the fixture.  To achieve Full Cutoff specifications (no light shining above the horizontal plane) the fixture should be aimed so the bottom of the shield is level and parallel with the ground as shown in the photo directly below.

The installed shield appears in the photo above

*** Important Notes ***

This type of shield should only be installed on floodlight bulbs that have a raised edge around the perimeter of the front lens.  A cross section of the bulb this shield is designed for is shown below.

Do not use this shield on bulbs that have a smooth surface around the outter perimeter of the bulb because this might lead to lamp implosion after the bulb heats up due to different thermal expansion coefficients and supplementary pressure introduced by the clamp.

Never install a shield of this kind when the lamp is turned on because of a possible electrical shock hazard and also because the lamp may be hot enough to cause a painful burn.  As a precaution be sure to shut the circuit breaker or remove the fuse for the electrical circuit that powers the light fixture before removing the bulb and installing the shield.

Check the condition of the rubber gasket on the lamp fixture to assure it is in good condition.  This gasket forms a water-tight seal between the lamp and the fixture socket.  If the gasket is cracked or has pieces missing, replace the fixture to remove a potential fire hazard.

Disclaimer

The installation and fabrication of this outdoor lighting shield is entirely at the risk of the installer and materials fabricator.  The author providing this information shall not be held responsible for any resulting injuries or consequential damages of any kind whatsoever.  Be careful when installing shielding or working on a ladder!  Assure the ladder is firmly in place and never stand on the top step of any step-ladder.  If your ladder is too short to reach the light fixture safely consider hiring an electrician to install this shield for you.

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