Here in the Gulf South, the nearly year-round heat and humidity can affect everything from our hairstyles to our air conditioning costs. But does it affect our buildings and the improvements we make to them? Absolutely, but that doesn’t mean we should forgo energy efficiency projects such as installing LED lighting, potentially missing out on thousands in savings. Rather, us Southerners need only be more careful about the materials and equipment we select, in order to maximize the lifetime of our upgrades as well as our savings.
When it comes to LED lighting, a lot of failures can happen due to outdoor fixtures that are poorly designed to withstand the Gulf South climate, or the elements in general. While a great company like Cree knows that outdoor lighting should be designed with an entirely different mindset from indoor lighting, some companies don't design with this consideration. As a result, there are huge differences in light quality between LED brands, including color temperature and light output, but also differences in the durability and longevity of the fixtures, both inside and out.
On the Inside: Drivers and Heat Sinks
Drivers are the computer-like components of an LED fixture that work with each diode to help extend its lifetime and retain the light quality. When a driver no longer effectively controls a diode’s output, color shifting may be exacerbated. Different colors will degrade at different speeds; blue light will degrade fastest, while red light will degrade slowest. This is why, as an outdoor light ages, it often becomes pink over time and appears dimmer overall.
You can avoid this rapid degradation by selecting an LED fixture with a high-quality heat sink that dissipates heat out of the back of a fixture, rather than allowing it to circulate throughout. But what makes for a good heat sink? The material used for the substrate can make a big difference. For example, Cree only uses silicon carbide as a substrate, which is among the most effective thermal sinks in the world. Most other companies use gallium nitrate, which is somewhat less effective but can still help dissipate heat.
The most important consideration is to make sure your fixtures were created with a heat dissipation strategy in mind, because this can make a big difference in their degradation rates.
On the Outside: The Finish
When it comes to keeping exterior fixtures looking great, it’s important to choose fixtures with a finish that withstands the elements and is substantially tougher than the finishes used on indoor fixtures. Cree delivers this with its DeltaGuard Technology, used exclusively in its outdoor fixtures and poles and covered in its industry-leading 10-year warranty.
The DeltaGuard finish application involves six cleaning stages, eight pre-treatment stages, and an epoxy e-coat before a topcoat is applied, which is baked on for durability. This finish stands up to UV light, corrosion, and other environmental conditions that your fixtures will inevitably encounter. So if you care about the appearance of your LEDs over time, make sure to inquire about the finish, and whether it is guaranteed to stand up to the elements.
The True Lifetime of LEDs
When referencing the stated “lifetime” of your LED fixtures, keep in mind that the rating may not be accurate for your specific location and application. For example, ambient temperatures in the Gulf South are generally much higher than those used to calculate ratings for outdoor lighting applications.
Spec sheets will calculate fixture lifetime based on a 25-degree Celsius (77-degree Fahrenheit) ambient temperature, and at the time I am writing this, it is 88 degrees Fahrenheit in New Orleans, with temperatures expected to hover around 90 degrees all week. But when it comes to ratings, Cree varies the estimated lifetime of its fixtures by region, so you’re more likely to get an accurate value.
For those LEDs that aren’t packaged as full fixtures and are used for lamp replacements, the stated lifetime does not take into account the fixture housing, which may shorten the life of the lamp. This is especially the case for fully enclosed fixtures such as some troffers and high bays, and those installed in spaces where temperatures can quickly climb, such as on the ceiling of an unconditioned warehouse.
If the enclosed fixture does not allow for heat to escape, the resulting convection can cause the lamp to degrade more quickly. In many cases, enclosing a lamp will also void its warranty, so in addition to shortening the lamp’s lifetime, you will also have to pay for a replacement out of pocket. So before purchasing lamps or fixtures, make sure they are appropriate for the space where you install them, and will be able to withstand the heat.
While selecting an LED fixture in the Gulf South is a trickier process than in most other places, the savings are well worth it. With the right LED brand and luminaire type, your lights could last several times longer than traditional fixtures, provide better light, and cost less to maintain. All you have to do is make sure they can stand up to the elements, and the lighting technology will take care of the rest.