Sustainable Landscape Ligthing Systems Overview
2008-08-01
Providing Energy-efficient, Material-efficient and Design-efficient Solutions in Outdoor Settings

Landscape lighting links people to the earth, the trees and the plants around them. Exterior lighting enables people to be comfortable outdoors after dark. It also improves security and safety at work, at home and at school and allows the natural landscape to be observed and appreciated after sunset. Minimizing the ecological impact of landscape lighting ensures that the systems designed to draw people into the fresh air are not, simultaneously, draining the natural environment or harming the plant life it was intended to feature.

Applying sustainable design considerations to landscape lighting, design teams can minimize the ecological footprint of those valuable illuminated hours. It is possible to save energy, reduce maintenance costs and material waste by selecting exterior lighting systems that are energy-efficient, material-efficient, and design-efficient.

Selecting Energy-efficient Landscape Lighting

Energy-efficient landscape lighting is not solely defined by minimal energy consumption. Instead, energy-efficient landscape lighting must accomplish all of the goals of a project using as little electrical energy and creating as little material waste as possible.

Identify Project Goals

To that end, the first step in specifying energy-efficient landscape lighting is to identify the goals of the space. Exterior lighting can be used for a wide variety of reasons: to highlight a cluster of tall trees or an elaborate architectural balustrade, to provide a wash of light over a large space, or gently illuminate a garden pathway. Every objective of exterior lighting requires unique consideration
in terms of what the light will need to accomplish. Design teams will need to identify the size of the area that must be illuminated, the ideal amount of light, the desired beam spread and the color of the light necessary to meet the demands of the project. Defining these characteristics will help determine the most appropriate lamp type for the project.

Distribution

The area that the light illuminates from its source, also referred to as the distribution, varies from lamp type to lamp type. For example, metal halide lighting typically has a larger distribution than a MR16 halogen lamp. This is important because illuminating a forty-foot tree from the ground up and highlighting a shrub are two very different projects in terms of the distance that the light must travel and, subsequently, the type of lamp required to accomplish the feat.

In order to design an energy-efficient lighting system, the distribution capabilities
of the light source and target area of the object must match. If the lamp selected does not appropriately reach the tree or wash the entire statue, it is not accomplishing the goals of the project. If the lamp selected is more powerful or has a greater distribution than the space requires, energy may be wasted as unnecessary light is provided.

Lumen Output

The amount of light produced by an individual lamp, also called the lamp output, varies from lamp type to lamp type. The lamp type used to create soft and interesting contrasts on an outdoor walkway will be different than the lamp selected to flood a space with security-level light when a potential intruder is detected.

Identifying the amount of light required in an outdoor space will help design teams select the lamp source that best matches the needs of the space, without supplying more individual fixtures or more light than necessary. The application determines the source.

The Beam Spread

The beam spread of a light source describes the degrees of coverage or angle of the light it emits. Often characterized in terms of spot, narrow flood, flood, wide flood, etc., some lamps are capable of providing a variety of beam spreads, while others may be limited to one or two. The available beam spreads indicate the ability of the lamp source to appropriately meet certain design goals, such as spotlighting statues on the lawn or washing an entire boulder wall in light.

For instance, beam spreads from linear fluorescent lamps are very wide. An excellent choice for lighting large offices for overall lighting but not a good selection for projects requiring task lighting, a spotlight, or even a narrow flood of light in a specified space. MR16 halogen lamps, on the other hand, can provide
multiple beam spreads and could be considered for a wide variety of applications from task lighting to accent lighting.

Specifying lamps onto a project that can provide the correct beam spread offers designers better control and more precise use of exterior light. Improved control saves energy and protects the surrounding houses or buildings from being washed in uncontrolled and unnecessary light.

The Color

Items look different under different types of light. The Color Rendering Index (CRI) assigns each light source a value that describes how the light it emits compares in color quality with natural daylight, which is considered the gold standard. Natural daylight has a CRI index rating of 100. In comparison, low-pressure sodium vapor lamps, the popular monochromatic parking lot light sources that bathe objects in an unnatural yellow hue, receive a CRI index rating of zero (0). The higher the CRI rating of a lamp source, the better the color quality of the light it creates.

When designing exterior lighting systems to highlight textures or materials used in the space, like marble or granite, it will be important to select light sources with higher CRI ratings to protect the integrity of the appearance of the material under the nighttime illumination.

Select Efficient Light Sources: Efficacy + Rated Life

Once the design goals of the space have been identified, it is time to select the most efficient lamp type capable of accomplishing those design objectives.

Two different factors are considered when determining the overall efficiency of a lamp type. Those factors are lamp efficacy and rated lamp life. The efficacy of a light source is measured in terms of the number of lumens produced per Watt. Higher ratios indicate more efficient light sources, because more light is being produced with less energy. Rated lamp life indicates the number of illuminated hours that one lamp is expected to last before needing to be replaced. Selecting a lamp type with a longer rated life will minimize the material lamp waste created throughout the life of the system.

There are a variety of light sources to choose from, but the most efficient matches for the outdoor environment are light emitting diodes (LEDs), compact fluorescent, metal halide and halogen lamps.

Halogen Lamps

Twenty five years ago, the halogen light source began outshining its predecessor, the incandescent bulb. Producing 15-20 lm/W and offering a much longer lamp life, halogen was more efficient in both energy and materials. As an added bonus that maximum efficacy is maintained throughout the life of the lamp.

Today, halogen lamps are available for both line voltage and low voltage and a variety of lamp types. The two most common halogen lamp types are a parabolic aluminized reflector (PAR) and a multi-faceted reflector (MR). The halogen PAR lamp is available only in line voltage. The MR-style low-voltage lamp is available in more wattages (20-75W) and a larger selection of spot or flood beams than the MR halogen designed for line voltage. Both lamp types produce a significant amount of heat while operating.

Compact Fluorescent Lamps

Compact fluorescent lighting (CFL) operates on line voltage (120 V and 277 V) and requires a ballast to help regulate the electrical energy running to the lamp. CFL consumes up to 75 percent less energy than incandescent lights and are able to generate 35-60 lm/w. The lamps last up to 10 times longer than the incandescent standards, illuminating outdoor areas for almost 10,000 hours per lamp.

Metal Halide Lamps

Metal halide lamps operate on line voltage and offer a longer lamp life and better efficiency than compact fluorescent, halogen, and incandescent lights. This lamp type requires a ballast to provide proper starting and operating voltages, which contributes toward the higher price tag often associated with metal halide fixtures. However, the higher initial cost is balanced by a low cost of ownership. Metal halide lamps will provide more light on a project, more efficiently, and for a longer period of time than the less costly halogen alternative.

Light Emitting Diodes (LEDs)

LEDs, also referred to as solid state lighting (SSL), are the newest and latest low-voltage light sources used in landscape lighting. Highly efficient, these sources are able to create 30-100 lumens/Watt. Beyond improved energy efficiency; the system life is much longer than other available light sources. LEDs are rated to operate for approximately 50,000 hours before needing to be replaced. This long life significantly reduces the maintenance required by the system and the number of lamps sent to landfills every year.

Although LEDs are highly efficient, they do generate some heat, so it is important that the lighting fixture is capable of heat management. Most importantly, the diodes are very heat sensitive and excessive exposure to heat will seriously diminish or completely fail an LED board.

Low-voltage or Line-voltage Landscape Lighting

The selected light source will determine whether or not the landscape lighting system will be low- voltage or line-voltage.

Line-voltage systems mostly use 120v or 277v supplied by the local power company. Your average home is supplied with an input voltage of 120 volts operating most household appliances.

Low-voltage lighting systems require a transformer to lower the line voltage. These products often operate with a voltage between 12v and 24v.

While both low-voltage and line voltage systems are excellent matches for exterior lighting, there are a few differences between the systems that are important to highlight.

Energy Efficiency

Line-voltage systems operate with a lot more power than their low-voltage counterparts. These line-voltage systems accomodate larger lamps with a much higher wattage, creating a significant electrical load with a small number of fixtures. In comparison, low-voltage lamps are physically smaller, available in lower wattages and able
to create more light with less energy.

Low-voltage lights produce 2.5 times as much light as line-voltage incandescent lamps. For example, a 50W low-voltage lamp generates as much light as a 125W incandescent lamp. This improved energy efficiency can create a savings of $7.50 per lamp every 1,000 hours of operation. This savings is based on an estimated cost of 10 cents per kilowatt-hour (kwh).

“In the past, landscape lighting in commercial areas was always line voltage. Now low-voltage lighting has advanced so significantly that a designer can use low-voltage instead of line voltage, provide the same light output in
the space and use remarkably less energy,” said Gabe Kauffman, a designer and installer at Landscape Lighting Design in Des Moines, Iowa.

Ease of Installation

Only a licensed electrical contractor can install line-voltage landscape lighting systems. When installing line voltage, the wire must be properly buried in the ground at least eighteen (18) inches and placed in a protective conduit. The required trenching, materials and expertise make line voltage systems laborious
to install and difficult to move, limiting the ability to modify the initial system design to accommodate the landscape as it matures.

In most cases, low-voltage lighting can be installed without an electrical contractor. Fixtures are powered and connected by an above ground cable that is easily camouflaged. No trenching or hardwiring is necessary, although the cable can be buried for cosmetic purposes. Ease of installation translates to easy relocation, allowing low voltage systems to be moved to complement the trees, shrubs, and foliage as they evolve.

Fixture Size

Line-voltage lamps operate with a much higher voltage, consume a much higher wattage, and are typically much larger than the low-voltage alternative. To house the larger line voltage lamps, the physical fixtures tend to be larger.
These larger fixtures are much more challenging to blend into the landscape. In comparison, the fixtures that house the smaller low-voltage lamps are also smaller and less obtrusive.

When selecting exterior fixtures, consider manufacturers that design low profile products. These landscape lighting products will provide the desired outdoor light discreetly.

Potential Electrical Shock

Any electrical system expected to work outdoors must be designed to deal with the elements. Lighting is certainly no exception.

While both low-voltage and line-voltage systems are designed to be safe outdoors, the danger represented by a low voltage shock is dramatically different from a line voltage shock. A transformer steps down the voltage being delivered to the low-voltage system. Once this occurs, approximately one-tenth of the original line voltage remains to flow through the wiring and the lamps. This significantly reduces the shock hazard. Shocks received from exposure to line voltage are very dangerous and potentially fatal.

Goal: Material Efficiency

Energy efficiency is not the only area of interest for teams trying to improve the sustainability of landscape lighting designs. It is also important to select products that are material efficient. The focus of material efficiency is the physical product, the life of the product, the impact that the product has on the environment from cradle to grave and necessary maintenance. When designing exterior lighting systems, selecting fixture materials that have zero or low toxicity, are highly recyclable, durable and built to last are all important
aspects of employing products that are material efficient.

Select Metal Fixtures

Lighting fixtures destined for the outdoors must be designed to accomplish two objectives. First, moisture must be kept out of the area housing the socket and the lamp. If the socket becomes wet, the fixture will short out. Second, the heat created by the lamp when it is illuminated must be managed. If too much heat builds up around the lamp, the lamp will overheat and fail prematurely.

The pursuit of this watertight and, simultaneously, cool environment is challenging because in order to keep dew, rain, snow, and other condensation away from the socket, the area must be airtight. In an airtight setting, neither moisture, nor air, nor heat can pass freely from the source to the exterior. Instead, the physical fixture becomes responsible for dissipating the heat.

The need to manage heat is the reason that high-quality outdoor fixtures are made of metal. It is also the reason that plastic fixtures are usually short-lived. Brass and aluminum effectively absorb the heat created by the light source, acting similar to a heat sink. The heat transfers from the lamp housing to the metal fixture and then radiates from the fixture into the environment.

Beyond functionality, another benefit of using brass and aluminum in the body of the fixture is that both metals are renewable and recyclable. Brass is the combination of copper and zinc and, today, almost 90 percent of all brass alloys are recycled. Aluminum is the most abundant metal in the Earth’s crust, and the third most abundant element overall, following oxygen and silicon. Soda cans, scrap metal, lighting fixtures and all other things aluminum can be recycled.

Improve Fixture Durability: Conversion Coating + Powder Coat

The durability and longevity of exterior lighting products are important aspects of their sustainability. If the products have a short lifespan, they will create more trash year after year than will a product that stands the test of time. If the product still works, but is an eyesore, it is not considered functional by sustainable standards either.

Metal is an excellent material to use for exterior lighting, because of its ability to absorb heat and be recycled. However, many metals, including aluminum, naturally corrode when they are exposed to water and oxygen. Corrosion weakens the metal, first forming a pit or crack in the surface, which then spreads, causing deterioration and the eventual failure of the product. In order for metal lighting fixtures to provide reliable performance in the wind, snow, rain, heat, humidity and salt spray, the aluminum must be protected against the elements.

It should be noted that when aluminum is exposed to moisture or air, it naturally forms an aluminum oxide layer on the surface of the metal. Unfortunately, this oxidized layer is non-uniform, provides poor corrosion protection, and creates a surface on the fixture that is difficult to paint.

Luckily, aluminum products and components can be protected against corrosion by being sealed inside and out with a pretreatment process called conversion coating and then finished with a dry coat of paint called a powder coat. The
conversion coating changes the surface of the metal to be more corrosion-resistant and to better grip the protective powder coating that will be applied to the metal after the conversion treatment has been completed.

The key to longevity for outdoor fixtures is to begin with a quality metal, such as copper-free aluminum. Then pre-treat the metal with a conversion coating to create a clean and corrosion-resistant surface and apply a tough powder coating that will protect the fixture from chipping, fading, cracking, or becoming otherwise
defective. This combination treatment of conversion coating and powder coating significantly improves the durability and lifespan of the exterior lighting fixture in even the harshest atmospheric conditions.

Aluminum components can undergo a conversion coating by either being dipped into a solution or sprayed. When dipped, the conversion coating not only bonds to the metal surface, but wraps around the entire product creating an extra protective layer. With a dipped conversion coating, even if the surface paint is compromised, the aluminum will not deteriorate.

A conversion coating that is sprayed onto the surface of the aluminum creates a protective coat that is thinner and more easily penetrated. The spraying process also has a greater potential for creating a less uniform coating, which, subsequently, impacts its effectiveness in the field.

The Differences in Conversion Coating

Today, the two most popular corrosion pretreatments applied to exterior lighting fixtures are non-chromate conversion and chromate conversion coatings. The environmental impact of these two processes is staunchly different. One process employs a toxic chemical that pollutes the environment, is dangerous to handle, and hazardous to dispose. The other pretreatment process exists in a closed loop water system where all of the water is treated on-site and then reused. The differences between the non-chromate conversion process and the chromate conversion process significantly impact the environment, and the durability and the sustainability of the product.

Chromate-based Corrosion Treatment

The chromate-based pretreatment is the most typical conversion coat used in lighting. This process is now strictly monitored by the Environmental Protection Agency (EPA) and most manufacturers pre-treat their aluminum components off-shore to minimize costs and regulatory oversight. These systems employ toxic chromium
compounds that pollute the environment and present grave problems with handling and hazardous waste disposal. Workers must be instructed in safe handling procedures, because chromates are acidic and will attack living tissue.

Special disposal requirements are in place to regulate the discarding of materials that include chromate compounds. One reason for the extra care is that chromates may cause spontaneous combustion if concentrated products are mixed with other substances, especially paper, rags, wood or flammable solvents. The Environmental Protection Agency (EPA) has classified chromium as a hazardous waste and requires that special measures be taken to remove the toxic material before the product is dropped into special, pre-determined landfills in the United States.

Another reason for the cautious disposal of chromate-treated materials is that the materials could contain hexavalent chromium. Hexavalent chromium (the dangerous toxin exposed in the film,Erin Brockovich) is highly toxic, a carcinogen and can have disastrous effects on the surrounding population if it seeps from a
landfill into the soil or water.

Exterior lighting fixtures that undergo the chromate conversion treatment are exposed to and contain hexavalent chromium. Because of the presence of hexavalent chromium in the metal, exterior lighting fixtures that have been pretreated with a chromate conversion process are not allowed to be sold in the European
Union (EU). The directive, entitled the Restriction of Hazardous Substances (RoHS), bans selling electrical or electronic equipment that contains hexavalent chromium in that EU in the hopes of preventing chrome from leaking into the soil.

Non-chromate Conversion Treatment

Over the past few years, a new, non-toxic, non-chromate conversion process has been developed. This non-chromate conversion coat process is completely safe, non-hazardous and environmentally responsible. It cleans and conditions
the substrate of the alloy through a non-toxic method to provide the long-term resistance to corrosion and tenacious adhesion to the protective powder coat required in a conversion treatment.

The active ingredient is de-ionized water-- water that has been electrically charged. This natural resource is a powerful metal cleaner. It reacts with the aluminum, penetrating the pores of the metal and removing dirt and impurities. In fact, de-ionized water is so successful at penetrating the surface of the metal that if left in the cleanser too long, the solution will start to etch the surface of the aluminum.

There are many steps in both the chromate and non-chromate conversion process. In the non-chromate process the best results are achieved if de-ionized water is used in each step. The use of water throughout the treating process does not create a lot of water waste. The non-chromate process exists in a closed loop water system that filters the water after each treatment and then reuses it, eliminating emissions and water waste. The material filtered out of the metal is simply dried and disposed of in the regular trash.

The non-chromate process creates corrosion-resistant products that are chromium free. These chromium free fixtures meet RoHS compliance and are welcome on the EU market and in the EU landfills.

Aluminum treated in the two different processes also performs differently. Chromate treatments dry and crack at temperatures above 150 °F. Non-chromate conversion coatings stay hydrated in temperatures up to 600 °F. The non-chromate method also provides a visual indication of the successful coating of the product
and identifies those areas that may require additional attention.

A Closer Look at the Powder Coat

Powder coating is the fastest-growing finishing technique in North America and for good reason. Powder coating applies decorative and protective finishes to a wide range of metal parts. The powder used in this process is a mixture of finely ground particles of pigment and resin, which is sprayed with a special spray gun that electro-statically charges the powder. The charged powder adheres to the electrically grounded parts. Then the powder is heated and fused into a smooth coating in a curing oven. The result is a uniform, high-quality and
attractive finish that is highly durable, as well as scratch- and chip-resistant. Powder coating can be done in a variety of colors, a wide range of glosses, diverse textures and different base resins to create a broad selection of coating properties.

Powder Coat Warranty

While the powder coating process may be described similarly from manufacturer to manufacturer, the durability of each powder coat can be significantly different. Warranties on conversion-coated powder coat outdoor luminaires are five years and more often than not these fixtures will retain their original finish. By contract
other inferior powder coating processes will need to be replaced up to eight times to match the lifetime of a more durable product.

The American Architectural Manufacturers Association (AAMA) is the group within the aluminum products industry responsible for certifying that a powder coat warranty is accurate. The warranty guarantees that the finish on the exterior aluminum fixture will withstand the elements for that specified period of time.

In order to verify these claims, the certification process places materials under a variety of stresses designed to simulate an extreme outdoor experience including intense heat, salt spray, boiling water and abrasion tests.

Efficient Design

While energy-efficiency and material-efficiency are important elements of sustainable design, they do not, by themselves, qualify a project as sustainable. The landscape lighting system should be designed to have low maintenance requirements and perform reliably every day, every year.

Efficient design begins by selecting quality fixtures that are both energy efficient and material efficient. Then incorporate those fixtures into the landscape in a way that minimizes the impact to the natural environment, is easily maintained, and works reliably.

Start with a Quality Fixture

Begin with a quality fixture. When a poor quality fixture is used it can break down often, outside-in or inside-out. The sockets can short out. The paint can flake or crack. The fixture may break, because it is not durable enough to withstand the wear and tear that an outdoor fixture receives. Poor quality fixtures do
not support sustainable design. They can become an outdoor hazard and the constant attention required to fix or maintain the system can cause homeowner headaches and high replacement expense in both time and money.

“The key to creating a sustainable project is selecting durable fixtures that are going to last,” said Gabe Kauffman. “Look for metal fixtures designed to withstand the elements and painted with a high-performance powder
coat that will protect the fixtures.”

Select a professional-quality outdoor lighting fixture from a major manufacturer. These fixtures are rated to withstand heat, moisture, salt, hail and more.

Good Wiring Design

Even though a licensed electrical contractor is not required to install low voltage systems, there are technical constraints in the design and installation of low voltage systems that can present problems to the inexperienced. If these technical considerations are not properly addressed, the system will not perform to an acceptable standard.

One of the major problems with larger low-voltage lighting projects is the voltage drop that occurs in proportion to the wire length and load. Good wiring design outlined by a professional is the best way to ensure that the landscape lighting system will work correctly.

Landscape lighting systems invite people to enjoy the outdoors after dark. By selecting an efficient lamp type that best matches the needs of the project and specifying a high-quality metal fixture that has been treated with a non-chromate conversion process, design teams ensure that this extra time outdoors is not bought at the expense of the environment. Using energy-, material-, and design-efficient systems, people can enjoy nature, after sunset, in a sustainable manner.