Since the 1990s, LED lighting manufacturers have sought the difficult balance of light quality, efficacy and cost. Because commercial white-light LED products are fundamentally blue LEDs, warmer color temperatures are particularly challenging – achieved at the expense of all three. But by adjusting white-light LED phosphors and advancing the technology of the blue LED chips (some mixed with amber or red LEDs), 2700K has become an industry standard.

Residential and commercial lighting designers choose the most advanced 2700K with superior color rendition for traditional interiors, for low-light settings and to blend with halogen sources already in place.

In 2011, lighting designers at the J. Paul Getty Museum at the Getty Villa participated in a US Department of Energy study on high-CRI PAR38 2700K LED replacement lamps – choosing 2700K as the best match to the warmth of halogen. The demonstration gallery was a resounding success, with about 83 percent energy savings. Since then, the Getty museums are gradually and subtly replacing their stock of halogen with LED.

“We use a lot of the LED retrofit lamps in some galleries, and in some galleries we still use halogen,” explained Kevin Marshall, head of the Preparations Department at the J. Paul Getty Museum in Los Angeles. High-CRI PAR-lamps are now readily available, but other lamp shapes have been more difficult. “We’ve recently found an MR16 that we like, and we’ve just found an AR111 lamp. Those were the two that we were looking for. Now we’re in the process of testing them to see if they’re what we really want.”

Marshall said that now he’s able to get the CRI and warmth he’s looking for, the energy and maintenance savings are a big attraction. He will continue to convert and to evaluate new products for low UV and IR – a particular concern in a gallery setting. To improve color, some of the new white-light LED technologies shift energy nearer both ends of the visible spectrum.

There’s 2700K LED and there’s 2700K LED
The sheer number of fixtures in a Getty museum makes wholesale conversion to dedicated LED fixtures uneconomical. But in most new construction in California, and even in small renovations, the new Title 24 energy code all but requires dedicated LED.

Pia DeLeon-Neumayr is a principal at PLUG Lighting, a lighting design specification showroom in LA. She’s using 2700K LED mixed with halogen in nearly every high-end residences she lights. “Good lighting has a very tactile quality. When I walk into a home I want to be able to feel the quality of the lighting. When the colors are warmer, it’s a more comfortable feel. And lighting is a big part of that.”

But, DeLeon-Neumayr warns, “there’s 2700K and there’s 2700K – it depends on which LED technology you’re talking about.” She frequently tests new LED products in her studio to see how they perform.

One important color factor not frequently included in manufacturers’ ratings is R9. This saturated-red swatch is used to test color rendering, but it is not one of the eight normally evaluated in CRI. Because red wavelengths are so crucial in evaluating skin tones, food, clothing, decorative items, etc., manufacturers will often advertise a high R9 value in addition to a 90+ CRI. Title 24 requires a R9 greater than 60 in all replacement lamps.

John Fox, design director of Fox & Fox Design in Seal Beach, CA, also demonstrates these premium products for homeowners: “I really need to be in the 95 CRI or higher to satisfy a high-end customer with wood floors and expensive marble. And showing it to the customer is key. A lot of times they’ll get a 2700K from some consultant or contractor and they look horrible.

“[2700K] got a bad rap early on. When the color spectrum was shifting to warmer hues, they didn’t have the ability to compensate with the higher CRI. You would up with a greenish off-color that didn’t work well.” Today’s improved spectra using multiple phosphors or different color LEDs produce that 90+ CRI with high R9 value. “That’s when you start to get a really good-looking 2700K, and you can even go lower than that, to 2200K.”

To blend or not to blend
“You cannot do a whole house with LED. It’s just not there yet,” DeLeon-Neumayr said. “It depends on the interior. If you have something modern and contemporary you can use more LED…. MR16s have come a long way, and we’ve been retrofitting a number of recessed fixtures with them, mostly in kitchens and task areas.” She appreciates the high efficacy in these high light areas, but only occasionally uses LED in bedrooms where dimming is the norm.

Fox disagrees: Though a client might purchase a decorative lighting element, he hasn’t specified a halogen source since 2009. “There’s no reason to go incandescent anymore.”

Fox added that as a lighting designer equipped with the latest LED and dimming technology, he no longer feels the constraint to choose a single color temperature for an installation. “It’s almost your biggest decision in every project.” A choice in color temperature will remain constant through bidding and substitutions, through program changes and selection of artwork and furnishings.

A new technology, generically called “dim to warm” combines white LEDs with amber or red, dynamically shifting the overall CCT as the light dims up or down. Varying color temperature with dimming eliminates one of the primary complaints about LED lighting and gives an almost-theatrical flexibility to the way spaces are designed and used.

Author’s Note: This article was inspired by a post on Randall Whitehead’s fine Light Makes Right blog: “Warm as Toast.” Look for more on dim to warm in a future issue of West Coast Lighting Insider.