Virginia, you've experienced one of the main issues with compact fluorescent bulbs that we can easily avoid with some education.  Be prepared to carefully scrutinize the packaging of bulbs you're evaluating, and keep in mind the following guidelines.

First of all, we must consider two rating systems currently used by the lighting industry to determine what color a bulb is relative to known sources such as incandescent bulbs or daylight, and just how real that bulb makes things look compared to a known source.

1. Correlated Color Temperature, or CCT, defines the warmth or coolness of a light source, and ranges from about 1,800 degree Kelvin (1800K) for a candle to a very cool north sky at over 20,000 degrees Kelvin (20000K). Our benchmarks are an incandescent bulb at 2700K, direct sun at 5300K, sun with blue sky at 6000K, and north sky at about 10000K.  Many offices and commercial spaces are lit with fluorescent bulbs that are 3000K or 3500K, which look cooler than an incandescent bulb.  Fluorescent bulbs labeled "warm white" are typically 3000K, while "cool white" bulbs are typically 4100K. Check out different color temperatures here.
2. Color Rendering Index, or CRI, ranges from 0-100 and indicates how colors appear relative to two benchmarks: incandescent bulbs, including halogen, and daylight. These both have CRI's of 100.  The closer to 100 the CRI is of a light source, the more natural and rich colors tend to appear.  Many newer fluorescent sources have a CRI above 80. Read more about CRI here or here.

The key to picking a compact fluorescent bulb requires carefully scrutinizing the packaging for information about color temperature (sometimes noted as CCT, if it is labeled at all) and color rendering index (almost always referred to as CRI). A recent trip to several local purveyors of compact fluorescent bulbs turned up mixed results: packaging sometimes indicated color temperature, sometimes did not.

Stick with products that label color temperature, which usually shows up on the packaging simply as "2700K", or in the product number with a number like "827". This is lighting industry parlance for a product that has a CRI in the 80's (hence the 8), and has a CCT of 2700K (hence the 27). Other likely combinations are 830 (CRI in the 80's, CCT of 3000K), 835 and 841.

Consider testing results from independent laboratories. In rigorous testing of color accuracy and color shift conducted by the Lighting Research Institute at Rensselaer Polytechnic Institute, compact fluorescent lamp color from Philips, Osram Sylvania and GE was more accurate with less color shift over time than products from SunPark Electronics of Lights of America.  See the test results at the end of this report.

Here in the mountain west, our light tends to be pretty warm, and an environment filled with dusty sage, buff and terra cotta looks most balanced with a warmer color temperature like 2700K - 3000K. One of the Denver Lighting Examiner's preferred compact fluorescent bulbs is Osram Sylvania's Living Spaces, which has enriched red color intended specifically for living environments, color temperature of 2700K, CRI of 82, and energy star rating. They are available locally at Lowe's.

Choose what color temperature is best suited to the intended use and desired feel of a space. Want a room to feel cool and conducive to intense concentration? Choose a cooler color palette with grays and blues and bulbs with a cooler color temperature, like 3500K.  Want to feel enveloped in warmth, soothed, and comforted, like you're curled up by the fireside or at your favorite restaurant under dim light?  Choose our warmer palette of buff, rich browns, and reds, and bulbs with a warmer color temperature of 2500K-2700K.

Originally posted 2010-02-16 00:01:41.

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Hi Doug. Your question is a great one, since lots of folks are now using compact fluorescent bulbs in their outdoor lights. Based on your comment about the bulbs looking too bright, it sounds like your fixtures might be lanterns that have a glass face so you can see the bulb.

Compact fluorescent bulbs (CFL's) can be successfully used in outdoor fixtures, but let's take a look at what we need to consider in order to use them successfully:

1. At night, the dark adapted eye does not need nearly the amount of light to see that is required under daylight conditions. This means that we do not need nearly the wattage in an outdoor fixture that we'd use inside. A 20W CFL bulb is MORE than enough (this equals 60-75 watt incandescent bulbs), and 13W or 10W bulbs (these equal about 40W incandescent bulbs) are even better.
2. CFL's require a minimum temperature to light up and to reach full brightness. The colder it is, the longer it takes a CFL to reach its full brightness. In a cold climate, like Colorado's, outdoor use of CFL's is a challenge in the winter.
3. The single biggest factor that affects fluorescent bulb life is the number of times the bulb is turned on and off. If you have a fixture on a motion sensor and it cycles on and off repeatedly, the bulb will fail much faster than one that is turned on and stays on for hours at a time.
4. CFL's are brighter to look at than incandescent lamps. This is particularly an issue in fixtures with glass fronts, which means that the light is spilling out in all directions. We want to choose fixtures where the bulb is not visible behind glass, or is at least concealed behind glass that's translucent and diffuse, not transparent.

So, how do we put all of these considerations to practical use?

• Use a much lower wattage bulb than what you would expect. In outdoor lighting, less is more!
• For fixtures in extreme cold or that cycle on and off frequently but don't remain on for long, use fixtures with integral LED sources or an energy saving halogen bulb. As LED technology continues to develop, LED replacement bulbs will likely be perfect for outdoor use, but they are not ready for the big time yet.  Stay tuned.
• Use twist-type CFL's only in enclosed fixtures or under eaves or overhangs, not in the open.
• Use fixtures with diffuse glass or, preferably, Dark Sky compliant fixtures, like these from Foothills Lighting.

In future columns, we'll address the importance of Dark Sky legislation, its links to both environmental sustainability and human health, and how to choose lighting that complies with Dark Sky standards.

Originally posted 2010-02-04 00:01:59.

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