Warm lighting feels natural to us in the evenings and promotes relaxation. As part of our natural human circadian rhythm, warm light seems to relax us and help us wind down for the day, and get ready for sleep. While cool lighting helps us be alert and energetic for performing tasks, cool lighting in our evening spaces may interfere with our inner clock.
We think of reddish light as warmer and bluish light as cooler. The color of light is expressed in color temperature, which relates to the temperature a hypothetical black body would radiate at various temperatures — and, perhaps confusingly, warmer colors are at lower color temperatures than cooler colors are.
The Color Temperature Scale
Colors on the color temperature scale that range from about 2700K to 3000K are called warm colors. These are the reddish or yellowish whites and are typical of incandescent lamps.
Incandescent bulbs emit light based on thermal radiation — the heat of the filament — so the color temperature is closely related to the actual temperature of the filament of the bulb.
Soft white compact fluorescent bulbs produce light at a color temperature of about 3000K.
Sunset and sunrise typically feature light in the warm color temperature range, a bit lower in number (about 1800K) than the light of a warm incandescent bulb. Moonlight is a bit bluer or cooler, in the 4100K range. Candle and match flames are typically in the range of 1700K to 1900K.
Why Warmer Colors Resonate With Us in the Evening
Perhaps warmer colors resonate with us for the evening because of the color of the evening hearthside fire. Warm light in the early morning, as might come in through an east-facing window, can also be comforting and help ease us into wakefulness. Whatever the reason, you can create the effect of warmth and comfort through lighting in the “warm” range.
Most of us do that with separate lighting sources. We open the curtains or blinds during the daytime and let the early morning warm sunlight in, then later the cool natural daylight. Then at night, we use incandescent lighting, and maybe a fireplace, to produce that warmer ambient lighting. If we want to read, we may have a fixture that throws cooler light on the screen or page.
As we age, the lens of our eyes can become slightly yellowed, and we may see colors as warmer. Because of that balancing, warm light with more cool light can be helpful as we age.
Warm Colors Change Our Perception
Warm colors in a room tend to change our perception of the color of objects within the room from how they would look in daylight. If your room is lit with mostly warm light, be sure to check out any furniture or other decor you're considering under a similar light, to avoid unpleasant surprises.
Too much warm light can tend to be a bit soporific, and make it harder to focus on specific tasks. That's why many office spaces are lit with cooler lights instead.
Also, remember when using lights that it's not just the bulb's color temperature that will affect the color of its light. If you're putting that bulb into a fixture with a shade or filter, the color of that shade or filter will change the color of the light.
Where Should I Use Warm Light?
Consider not just the choice between warm or cool light, but where and when to use each. You will likely want some mixture of cool and warm light in a space, and it's especially helpful to have separate controls for "scenes" that require different ambiance.
Warm, or soft white, light, is especially appropriate for cozy living spaces where we want to relax and be comfortable. Use warm lighting to simulate evening or very early morning light. Use cooler lighting for tasks that require a lot of focus. Warm lights look better in many period rooms, and especially those with warm colors in them.
A warm white bulb is a common choice to replace older incandescents.