Have You Considered "Composite" Landscape Lighting Fixtures? By Janet Moyer When a client asks a lighting professional to design and specify landscape lighting, that professional takes on a responsibility to ensure that his or her design will endure the harsh outdoor environment for many years. This means that the designer must understand the construction of lighting fixtures and the materials and finishes used in making fixtures. Recently, some lighting manufacturers have begun offering fixtures manufactured from a "composite" material as part of their line of outdoor products. This means a designer needs to think about several issues when selecting a long-lasting fixture; how composite materials compare with metals for use in outdoor fixtures; and what we can expect to see from composites in the future. For many years, the standard materials for landscape lighting fixtures (not including submersibles, for that is another topic altogether) included primarily metals--bronze, brass and aluminum. Bronze and brass offer good structural strength and hold up well outdoors, but fixtures made of these metals are very expensive. Until recently most landscape lighting fixtures have consisted of aluminum alloy material, surrounded by a protective "coating." By using aluminum rather than bronze or brass, manufacturers were able to offer fixtures at a lower cost. However, the problem with making fixtures from aluminum stems from the fact that most aluminum alloys do not have strong corrosion resistance. In order to improve the corrosion resistance, manufacturers had to add a protective coating on the surface of the aluminum alloy. The criteria that determines whether an aluminum fixture will last outdoors depends on the selection of the alloy, the type of pre-treatment finish, and the type and application of final coating methods. Of the many aluminum alloys available, those with a minimum percentage of copper content have the best corrosion resistance. Anodizing and powder coating comprise the standard finishes used today. Both finish procedures include limitations, require careful selection of dyes (anodizing) and resin (powder coating) and have critical standards and processes for pre-treatment. A number of years ago, plastic "Landscape Lighting Kits or Sets" became available as commodity products at discount stores and home centers. These lighting fixtures consisted of a plastic material that did not offer much structural strength, and so were easily broken within a short time of installation in a landscape. Typically employing a low voltage PAR36 lamp, these fixtures offered a poor choice for most landscape uses and consequently added to the unflattering reputation that these "Lighting Sets" have given to plastic fixtures. For the last several years, some lighting fixture manufacturers have been producing a category of fixtures for landscape lighting made of a kind of plastic typically called "composite." High quality composite plastics can offer better structural strength than the "lighting sets," good corrosion resistance, good UV resistance, and a lower cost than comparable metal units. Still, additional issues of exterior durability and heat dissipation capabilities need to be considered when a designer is deciding to specify a composite fixture. Basically, the composite plastics used for fabricating landscape lighting fixtures consist of a polymer that may need one or more additives to provide corrosion and UV resistance. All quality composite materials used for landscape lighting fixtures have glass fiber reinforcement for strength, stiffness and durability. For a composite fixture to be useful in landscape lighting, it needs to have the following properties based on resin selection and fixture design: enough structural strength to be physically abused by shovels hitting it, kids kicking it, and electricians or lighting designers trying to aim and adjust it; excellent chemical, solvent, and biological resistance so that it does not corrode; ample room to accommodate for the heat of the light source (approximately 400o F); and the ability to withstand thermal shock. Perhaps the best type of resins used today are the glass-filled thermoset or thermoplastic polyesters. After finding the fixture manufactured from an appropriate resin or combination of resins, such as the Rynite??????oe PET (polyethylene terephthalate, a thermoplastic polyester resin) and Ryton??????oe PPS (polyphenylene sulfide) resins, lighting designers also need to consider the following when selecting any outdoor fixture: aiming capacity, locking mechanism, ease of lamp access for relamping, gasketing, and anti-siphon protection to eliminate any water penetration. Two production methods exist for fabrication of composite materials--injection molding and compression molding. Injection molding allows for an intricate form, while compression molding requires a simpler shape due to manufacturing limitations. Molding fixtures require tooling, a process that eliminates the ability to easily make slight modifications such as changing the hood size or shape for better shielding. Another limitation a lighting designer should consider when contemplating specifying a composite fixture is the response of the material to heat. Composite fixtures have to be larger in size than comparable metal fixtures in order to compensate for heat buildup. The availability of color selection may also limit the designer; fixtures can be manufactured in black, bronze, or white, but some makers typically only offer one color. Unlike specifications for powder coating of metal fixtures, the designer's ability to get relatively inexpensive custom color matching is not an option at this time. Most lighting companies have concentrated their efforts on producing direct burial fixtures, partly due to the fact that the most detrimental corrosion occurs below grade, and partly due to easier acceptance of slightly larger fixtures in below grade applications. Once a manufacturer decides to commit to offering a composite fixture, he or she undertakes a significant tooling cost. After that initial investment, and partially due to the elimination of the pre-treatment and painting steps required for metal fixtures, the production costs for a fixture drop. Some manufacturers offer composite accent light fixtures as well. Most of the lighting producers in the United States either already have composite fixtures on the market or are preparing to introduce some. Kim Lighting, who was adamantly opposed to using composite materials in the construction of landscape fixtures, has spent the last few years thoroughly researching the competition's fixtures in the field and the materials that are available. The company now agrees that there is merit in considering composites, but feels like it is still some time away from solving its remaining concern: a tendency, for at least some of the materials currently in use, to dry from heat exposure from the lamp and from UV exposure, resulting in the material chalking, drying out and becoming brittle, and in some cases even lifting fibers from the fixture body. Greenlee Lighting, one of the first manufacturers to introduce composite fixtures, is now working on its third generation of materials. At the 1996 ASLA National Conference in Los Angeles in October, the company will debut three new fixtures made from post-consumer recycled material, which is easier to mold and has a higher continuous UL rating of 155oC than its previous products. Greenlee is also continuing to research the possibility for offering additional UV-stable colors including "Formica surface" options that coordinate with hardscape surfaces. Likewise, Hadco, which produces 12 and 120 volt above and below grade fixtures and now includes path lights in its line of composite fixtures, remains committed to composite fixtures as an option in its line. To date, no lighting producers have announced plans to limit the availability of metal fixtures. This is partly due to their belief that metals such as bronze, brass, and stainless steel still offer the best combination of manufacturing options and corrosion resistance. Lumiere, for example, offers a 12-volt accent light for stake or mounting canopy and several 12 and 120 volt below grade units, but wants to be able to supply metal when the designer or client prefers it. Lumiere, along with several other makers, still shares a lingering concern for the future of composites, due to the reputation of plastic fixtures caused by widespread bad experiences of consumers who purchased and installed "Landscape Lighting Kits or Sets." BK Lighting, while committed to pursuing composites, suggests that they are best utilized for below grade fixtures. The company feels that stake mounted accent lights, which experience splash and a resulting dirt build-up that can lead to deposit corrosion, can endure corrosive conditions when manufactured from the proper aluminum alloy, with the appropriate chromate conversion coating pre-treatment and use of stainless steel fasteners. Each of the manufacturers consulted during development of this article expressed a strong commitment to composites and foresees the market continuing to grow at a rapid pace. The bottom line remains that each wants to make sure that lighting specifiers understand the limitations of composites and use caution in their selections, so that the industry as a whole can overcome that unfortunate "plastic fixtures are cheap" reputation.