Light Temperature: How it Affects You and Using it in Your Home

Light isn’t just about brightness. Light also has a temperature, which corresponds to its hue. Learn about what light temperature is, and how it can work in your home.

Have you ever had that experience where, after changing a light bulb, the space you’re in looks completely different? Sometimes, this can happen because you switched an incandescent bulb for another with a different wattage, essentially making the room much brighter or darker than you are used to. Other times, this change happens when you switch from, say, an incandescent bulb to a CFL bulb. The the warm, comforting light you associate with home has suddenly become the colder, more impersonal light you associate with your dentist’s office.

Yes, the level of brightness in a room has a lot to do with how it feels, but there’s another aspect of light that people sometimes struggle to put their finger on (despite immediately recognizing that something about the light conditions in a given space seems “off”).

That seemingly unnameable difference is what we call “light temperature.” You’re about to find out that there is a significant amount of science behind that uneasy feeling you get in overly poor, or overly harsh lighting conditions.

Let’s take a look at all the interesting things going on here, and why they affect us so much as human beings.

What is Light Temperature?

Picture the flame emanating from a stovetop gas burner, or perhaps a propane grill. The temperature in the center of that flame is much hotter than the edges, and we can tell this at a glance because the color of the flame changes. The extremely hot flames in the center glow a brilliant blue, and as you move outward, the color changes to a bright white, to yellow, and finally to a fiery orange.

Another example would be the daily cycle of the sun. During the hottest part of the day, the sun lights up the sky a bright blue, but the closer the sun is to the horizon, the more that color changes. The sky may be painted in yellows in the late afternoon, oranges in the early evening, and finally red at twilight. The more directly overhead the sun is, the brighter the colors seem to us here on the ground.

This color changing phenomenon is the basis for measuring light in terms of temperature – or more to the point, in degrees Kelvin. The higher the light temperature, the brighter the light will shine.

Confusingly, people tend to refer to light with higher temperatures as “cold light,” and light with lower temperatures as “warm light.”

To help you sort out how different types of light are measured in degrees Kelvin, let’s reference some everyday light temperatures you may encounter:

• Clear blue sky – 10,000+ degrees Kelvin
• Cool white LED lights – 7000° Kelvin
• Computer monitors – 6500° Kelvin
• Midday, cloudy sky – 6000° Kelvin
• LED lights meant to mimic daylight – 5500 – 6000° Kelvin
• 100 W halogen light bulb – 3000° Kelvin
• 100 W incandescent light bulb – 2800° Kelvin
• Warm white LED lights – 2700° Kelvin
• Sunset/sunrise – 2000° Kelvin
• Candlelight – 1900° Kelvin
• Burning embers – 800° Kelvin

Since light temperature so closely corresponds with light color, this helps explain why your home can suddenly look and feel very different simply thanks to swapping out one lightbulb for another. For the most part, we humans enjoy what we call “warm white” or “soft white” lighting for inside the home. This will fall around 2700° Kelvin, and have a noticeably yellow tint to it. Take a look at any floor lamp in your home, chances are the color shining through the lampshade appears more yellow than anything else.

Incandescent bulbs almost universally give off light that measures around 2800 degrees Kelvin, and therefore appears yellowish. Because incandescent bulbs have been the default lightbulb for well over a century, it’s safe to say that most of us grew up used to seeing our homes illuminated in yellows and whites.

But now, thanks to advances in technology and market competition lowering prices, the average consumer has access to a much wider range of light technology, and therefore may unexpectedly experience a fairly drastic change in light temperature.

CFL bulbs (compact florescent lighting), what you might know better as “those twisty lightbulbs,” were presented as a more energy efficient alternative to our trusty old incandescents. That much is true, CFL’s consume far less energy than incandescent light bulbs do. There was just one problem – they sometimes made everything look terrible.

This is because CFL’s tend to cast light that measures close to 4500° Kelvin, representing an unexpected 1700° jump in light temperature which some consumers immediately disliked. This change in light temperature was enough to take their home from a cozy, soft, yellowish light to a colder, more severe blueish light.

Developments in LED technology have expanded the light temperature range even more, as these lights can range from a soft white that looks like an incandescent, to something much brighter, and closer to natural daylight.

The Physiology of Light

Our well-being is tied to light conditions more than we may realize. There is a health concept known as circadian rhythm which describes the human body’s natural response to daylight, darkness, and everything in between.

Before we had such a vast selection of indoor lighting, and such abundant access to energy, human beings relied mainly on the natural progression of sunrise and sunset to dictate active times and rest times. The sky gradually brightens, prompting our brains to begin the process of waking up, then, we reach full alertness and productivity once daylight fully arrives.

Likewise, the gradual darkening of the sky signals to our brains that the time for rest is approaching, and that we should begin to wind down our productivity in preparation for sleep, which happens when it is fully dark.

The harnessing of light may have disrupted our circadian rhythm pretty severely. The problem was likely not as noticeable when the only type of light available to us was fire, but with the invention of the electric incandescent light bulb, human beings were able to keep light in their lives for more hours, and therefore stave off the natural sleep/wake cycle to a more convenient time. Flash forward to today where we have bright computer screens shining directly into people’s faces all day, and the problem has only grown more severe.

Consider this: in the list above, it was stated that computer screens have a light temperature of approximately 6500° Kelvin (same goes for your phone). This is the same light temperature that one could expect on a cloudy day, or on a sunny day in the shade. Either way, the point is that it’s light you can expect during the day. Therefore, staring at a computer screen at night, or paging through your cell phone before you go to bed is sending signals to your brain that it is actually midday, and that you should be awake.

And this day/night confusion extends out to our whole system. When the brain is exposed to bright light such as what is available in the middle of the day, or that which shines from a computer screen, the production of the hormone melatonin decreases, sending signals to your entire body that it should not be sleepy right now. Many people who suffer from insomnia are advised not to look at screens in the hours approaching bedtime, for just this reason.

Of course, the medical industry has understood that light can affect humans in drastic ways for quite some time. Seasonal affective disorder is a diagnosis given to patients who struggle with depression, low energy, and excessive sleepiness. Typically, these symptoms strike in the winter months, when the days are shortest and nights are longest. The lack of abundant daylight can disrupt energy levels and productivity in otherwise healthy people.

There are many different treatments available for seasonal affective disorder, but one of the more interesting ones is light therapy. This treatment involves a patient being exposed to bright lights (8000° Kelvin and up) for a prescribed amount of time to help even out hormone production, and increase productivity and mood.

Of course, the mind and body go hand-in-hand. Light can affect psychology just as much as it affects physiology.

The Psychology of Light

One of the Emmy awards given out every year is for “outstanding lighting design.” When it comes to entertainment, photography, or even marketing, a great deal of thought goes into lighting, because it can very directly affect your mood.

Picture this: a photograph of a home taken in broad daylight, versus the same home photographed in the dark, with strategic lighting meant to increase dramatic shadows. One of those pictures will look cheery and inviting, while the other will look eerie, and possibly even dangerous. We take a lot of psychological cues from the light around us, and photographers as well as the entertainment industry put a great deal of work into conveying feelings with light.

In your home, you probably even have some light psychology at work without realizing. If you have chosen soft reading lamps with a lower light temperature in a bedroom over a harsh overhead fixture, you probably did that because the softer light fits the mood and purpose of a bedroom better. Likewise, if you have abundant illumination with high light temperatures in your kitchen, you did that to help increase productivity and energy in the room.

Perhaps the best example of light temperature affecting mood is how you feel on a sunny day, versus how you feel on a rainy day. On sunny days, people are more likely to feel energetic, cheerful, and productive. On a rainy day, people are more likely to feel exhausted, irritable, and quiet.

So, the question now becomes: what is the best light temperature for your home?

Applying Light Temperature to Your Household

Having read all this information about light temperature, and how it can affect you physically and psychologically, you have probably already guessed that there is no single light temperature that will work for your entire home.

Finding the right light temperature for each area of your home is extremely important, because it will dictate the look and feel of your rooms as much as any other aspect of interior design. Have you ever had the experience of choosing the perfect paint color in the hardware store, but then realizing that it looked terrible when it was actually on your walls? That difference is not in your head. It has everything to do with large differences in light temperature making colors appear drastically different.

So what is the best way to maintain a good light level in your home that will work for a variety of needs? The answer to that is light layering.

Here are a few guidelines about light layers to remember:

• You can achieve good base uniformity by choosing a color temperature you like (most people choose something between 2800 and 3500 degrees Kelvin), and using it as the ambient light for every area in your home. This will smooth transitions between areas, and offer a good level of illumination all throughout the house.
• Lights with higher temperatures are good for productivity, and anything requiring attention to detail. Task lighting, reading lights, and vanity lights all work best when a higher light temperature (Around 4000 – 5000 degrees Kelvin) is layered on top of lower temperature ambient light.
• Accent lighting, or lighting meant to draw the eye to a particular area, piece of furniture, painting, etc. should be approximately three times brighter than ambient light in the room. So, this light will have the highest temperature of all your light layers – sometimes up to 10,000° Kelvin or higher. Accent lighting will tend to be bright white, to bluish in color so that it can outshine all other light sources.

Of course, each individual home will have its special circumstances to consider. Homes that are shaded by many mature trees will need extra lighting to prevent the house from being too dark during the day. Homes with many windows and skylights will be layering their interior lighting on top of abundant daylight.

No matter which set of lighting challenges you’re looking to overcome, and no matter how you want your home to look and feel, one thing everyone can benefit from in interior lighting is versatility. The ability to switch from low temperature light to high temperature light with the press of a button, the ability to raise or lower the light level in a room as needed, and the ability to direct light in certain ways is all very valuable – and until recently, it was also very difficult to accomplish.

The advancements in LED technology over the past few years have brought a huge range of lighting capability and versatility to the consumer. You can design lighting which not only helps to promote a certain mood or feeling in your home, but which can also fit more naturally into our circadian rhythm.

Plus, LED lighting works very well with smart technology, so lighting cycles can be pre-programmed to follow certain patterns, or remotely controlled from a smart phone or other device.

We’re not limited to a single lighting choice anymore, and as a result, we have greater control over how the light in our homes affects us physiologically and psychologically. These advancements make our homes more beautiful and welcoming, but they can also help maintain our natural sleeping and waking cycles.