Hi, Lisa. I really want to save energy by using compact fluorescent bulbs in some of my light fixtures, but the last batch I bought was an awful cold blue color that made me feel funny. How can I avoid making the same $9 mistake every time? – Virginia, Cherry Hills Village
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.
- 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.
- 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.
Lisa Barter is a lighting designer with extensive experience in the architecture and interior design fields. She is the principal of 3i Design, LLC, a lighting design and interior architecture consulting practice. She welcomes your questions and ideas, and you can reach her here.