CFL Downlights Put to the Test
March 7, 2012 - 4:23pm

These days, it seems everyone is in love with recessed downlights.

“For the past 25 years or so, the trend in residential new construction and remodeling has been to install recessed downlights as the predominant luminaire,” said Patricia Rizzo, residential program manager at the Lighting Research Center at Rensselaer Polytechnic Institute. “Their clean, low-profile appearance appeals to many consumers.”

And these days, people are also in love with the idea of saving energy by installing energy-efficient lighting in their homes, often by replacing incandescent bulbs, which lose a lot of energy to heat, with compact fluorescent bulbs, which lose less.

Normally, CFLs have a lifespan that’s up to 10 times that of an incandescent lamp, but when CFLs are installed in recessed cans, they’re not nearly as energy efficient as you might think. That’s because CLF downlights require the use of a ballast, which is a piece of equipment that resists the flow of electricity to the light, and when the ballast exceeds a certain temperature, it fails, causing the light to fail.

The problem mainly arises when the recessed cans are installed in air-tight fixtures in insulated ceilings. Normally, air-tight fixtures help stop heat from escaping into the attic or the outdoors — a good thing when you're using incandescent bulbs. But when you’re using CFLs, an air-tight fixture keeps the heat in and raises the temperature of the ballast to a point where it reduces its effectiveness.

So to evaluate the energy efficiency of CFL residential downlights, Rizzo and other professors at the Lighting Research Center performed tests on various types of CFL residential downlights to evaluate the amount of electricity they used, the light they outputted and the amount of heat they generated. The organization released its final report in January.

According to the report, entitled, “Specifier Reports: CFL Residential Downlights”: “Heat management is particularly important for CFL downlights. Heat can impact the performance of both the lamp and ballast in a downlight. In [Insulated Ceiling Airtight]-rated luminaries, airflow and heat dissipation are significant issues. Incandescent luminaires do not react adversely to temperature variations; CFLs, on the other hand, are very sensitive to ambient and local temperature fluctuations.”

The study looked at 12 different types of Energy Star-rated CFL downlights and tested them in both open-air conditions and enclosed conditions to see how hot the ballasts got after leaving the lights on for eight hours to stabilize.

In the open-air test, the Halo H272ICAT lamp and the Thomas PS126 Maxilume ES/HH6PLIC lamp both had the lowest recorded temperatures; NuTech’s RZ126 lamp had the highest temperature. All 12 lamps, however, came in under the maximum allowable temperature, set by the Underwriters Laboratory.

In the enclosed temperature test, which simulated a recessed can in an insulated ceiling, Halo’s H272ICAT again had the lowest temperature for the ballast, while Prescolite’s IBX26ICAT had the highest recorded temperature.

The study also looked at how much light the lamps emitted vs. how much light their manufacturers claimed they emitted.

In this case, all of the lamps only emitted 36 to 53 percent of the light that their manufacturers claimed due to differences in system operation.

To read the complete study, please visit the Lighting Research Center at

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