
Looking for a guide to simulate sunlight indoors? You’ve absolutely come to the right place!
What if I told you there was such a thing as mal-illumination? Similar to malnutrition, it’s when you’re deprived of biologically necessary light.
Many of us spend large portions of our day completely disconnected from natural sunlight. In the winter months, we may even go entire weeks without spending a moment in the sun!
Instead, we bask in man-made light spectrums that pay no heed to our ancestral origins or biological needs.
These spectrums often have wildly unnatural visible wavelength ratios and are completely lacking all beneficial infrared and ultraviolet wavelengths. Not to mention, the dimness that often accompanies these environments is an issue all its own.
This is obviously untenable if we hope to stay functionally healthy for a long period of time. Human beings need full-spectrum light exposure for optimal health.
Full-spectrum sunlight is necessary for optimal eyesight, digestion, sleep, movement, repair, and detoxification.
Of course, since we spend a large portion of our time inside structures that block most of the natural light from the sun, we must consciously work to bring these missing spectrums back into our indoor spaces.
If we hope to emulate it, let’s first go over just what sunlight is.
The Qualities of Natural Light
The only natural source of radiation comes from our Sun, and all life on Earth has adapted to this form of energy over the course of billions of years.
What is Sunlight Made Out Of?
Let’s start with the spectral makeup of natural light so that we can better conceptualize what we need to copy.
Below is a spectral distribution graph of sunlight as it passes through the atmosphere.

This can be broken down into roughly the following percentages:
- UVB: <1%
- UVA: 8%
- VIS: 44%
- IRA: 32%
- IRB: 14%
- IRC: 2%
As you can see, most of the energy coming from the sun is in the visible band, and it’s fairly even across the board; although there’s usually a slight bump in the blue-green area throughout most of the day.
There’s also a fair amount of UVA and tons of infrared energy in sunlight.
The Color of Sunlight
The appearance of sunlight changes throughout the day in relation to the amount of high-frequency light it contains.
The color of sunlight and all artificial sources of light are expressed in Kelvin, or the apparent “color” of a heat source. As the heat source rises in temp it becomes “cooler” in appearance.

The color temperature of sunlight in space is about 5900K, but by the time it reaches the earth on a clear summer day, this dips down to about 5200K to 5700K due to the Rayleigh scattering of the shorter wavelengths, hence the blue sky.

As you can see, throughout most of the day (9AM – 6PM) the color temperature of the Sun was between 5000K and 5700K.
And below is a minute-by-minute spectrograph capture of sunlight from 7 am to 12 pm for an idea of how sunlight changes during sunrise.
When it comes to choosing artificial lighting, you’ll be looking for lights that correlate with this trend by choosing something >5000K for the daytime, and <3000K for the evening.
Natural Light is Bright and Powerful!
One of the most important aspects of natural light is that it’s very bright!
The radiation hitting the Earth at the equator peaks at about 1,120 W/m2. Over the course of a year, this averages out to around 340 W/m2.
All of this power culminates in a very bright source of light, with sunlight producing about 93 lumens per watt. Meaning, at equatorial noon we should see about 104,160 lux (lumens per square meter).
If we averaged an entire year over all locations on the Earth’s surface, the average solar irradiance would be about 170 W/m2 per day and about 16,000 lux. These change based on the specific area, if we’re in cloudy Scotland, the year-long daily average is closer to 72 W/m2 and about 7,000 lux.
As you can see, the Sun is a powerful, bright radiating machine, and the brightness of our indoor environments usually pales in comparison.

One of the most beneficial things we can do for our health is to simply increase the brightness of our interior lighting.
This can be done in a number of ways, which we will go over. However, know that at this time it’s generally quite expensive to drastically increase the lux in your home using high-quality LEDs.
My Thoughts on Lux Levels
I think it’s probably more important to increase the lux levels in a room than it is to fill a room with high-quality, yet dim light.
The average room is maybe 500 lux if you’re lucky, while on an average clear day, it’s 60,000+ lux outside at eye level.
There’s easily 120x more energy entering our eyes and skin when we’re outside.
This massive decrease in energy, when we go inside, is what leads to mal-illumination.
Is it any wonder everyone complains of bad sleep and poor energy?
And the severe lack of infrared energy hitting our cells is contributing to metabolic dysfunction in just about everyone.
So we’ll go over some of the various ways to increase the lux levels in your most occupied spaces.
Light Flicker
Artificial lights, for the most part, flicker at various frequencies due to the alternating current powering them.
The sun, on the other hand, stays at a very steady brightness throughout the day.
Once a light’s flicker rate reaches a certain threshold, called the critical flicker fusion rate, the human eye starts to see it as one average brightness.
But! Just because we can no longer visually perceive it doesn’t mean it’s gone. What we’re left with is termed “invisible flicker”.
Now, this invisible flicker comes in many styles. Some lights flicker at 120hz or 120 times per second, just outside of our perception, while others flicker at 10,000hz and beyond.
And some don’t flicker at all, much like sunlight.
The question is, does this invisible flicker matter? It is invisible after all.
And surely humans have some adaptation to flickering lights, right?
Think of tree canopies shifting in the wind or running through the forest. Or dancing firelight.
However, if you peruse a website like ledstrain.org, you’ll see that there are many people who seem to suffer in the presence of invisible light flicker. Perhaps they’re the canaries in the coal mine?
The IEEE has set an optional industry standard for flicker with Std. 1789. They looked at all the available data and created a rough guide for flicker safety.
It looks something like this:

However, it should be noted that these are just best guesses at this time, as the science of invisible flicker is very understudied.
Either way, the suggestions we have later in the article will include these metrics, so you can avoid these issues if you feel it’s worth it to you.
How to Get More Natural Light Indoors
Now, before we begin adding artificial “sunlight” to our homes and offices, let’s make sure we’ve done everything we can to let in real light first.
1. Let the Light in!
Let as much light in as you can by opening your blinds and windows. If you have an issue with glare, it would be better to apply anti-glare film than to cover the window with curtains or blinds.
If only a portion of your window is the trouble spot, you can choose to apply a small portion of the anti-glare film, so that more light can get through the rest of the window.
2. Get as Close as You Can
Wherever you spend most of your time, most likely in your office or family room, make sure it’s near a window. At work, try to get a location nearest a south-facing window, east would be second best.
3. Hardwood Floors are Better than Carpet
Hardwood floors will reflect more light into a room than carpet will, and light floors will reflect more than dark. Something to consider for future renovations?
4. Selecting Paint Colors
Wall color hues with more white in them (think lighter) will reflect more light around the room. Go with a satin variant here to maximize reflections without making imperfections too obvious.
Since north-facing areas of the house will get bluer light, you can paint warmer hues there, while south-facing windows will receive warmer light and could stand to be painted cooler colors.
This will help even out the colors reflected into the house into a more even color tone.
5. Add Privacy Window Film
If privacy is a concern with certain windows, try applying window film. This will allow you to feel secure while still allowing sunlight in.
The Science Behind Full Spectrum Visible Light
Visible light is the portion of sunlight responsible for setting your circadian rhythm, meaning it’s the most important part. If you choose to implement only one part of the spectrum of sunlight, this would be the one.
The beneficial effects of bright full spectrum light are too numerous to count.
This is a resource section for anyone who wants to explore the science a bit more or needs some intellectual ammo at work for why you want to change your lights.
- A Literature Review of the Effects of Natural Light on Building Occupants cites hundreds of examples of bright full-spectrum light being beneficial in every scenario imaginable. [R]
- Ambient lighting brightness appears to be very important for proper refractive development in young animals, with dim light being significant in myopia development. [R]
- Exposure to sunlight and ultraviolet light is associated with a decreased incidence of myopia development. [R]
- Bright ambient lighting retards the development of form-deprivation myopia in monkeys. [R]
- Recovery from form-deprivation myopia in chicks was significantly better under full-spectrum LEDs when compared with fluorescent light of the same color temperature. [R]
- In a study of 27 children, the majority had better eyesight under a 5500K color temp light vs 3600K. [R]
- Time spent outdoors in bright sunlight reduces the chance of developing myopia. [R]
- Bright light exposure at home is associated with less sleep disturbance, anxiety, stress, and depression. [R]
- In a group of call center workers, switching from a low CCT light source (2900K) to a high CCT (17000K) resulted in improvements in well-being and work performance. [R]
- Bright light sufficient to trigger a circadian response improves sleep, mood, and behavior in dementia and Alzheimer’s patients. [R]
- In this study, hens preferred spending time under bluer fluorescent lighting over incandescent light of the same lux. [R]
- In a study involving 313 workers, exposure to more full-spectrum sunlight resulted in 63% fewer headaches, 56% less drowsiness, and 51% reduced eyestrain. [R]
- Evening melatonin secretion and peripheral heat loss occur earlier in office workers exposed to brighter light. [R]
- Exposure to adequate amounts of blue light is necessary to set the circadian rhythm and bring about a massive cascade of biological processes on a daily basis. [R] [R]
- High energy wavelengths like blue light can cause retinal damage, it’s important that lighting is bright enough and even across spectrums so that the retina is properly dilating. [R]
- Diurnal rats lose about 30 percent of hippocampal capacity and perform far worse on spacial tasks after four weeks in dim light. [R]
- Workers near windows had higher melatonin levels and lower cortisol at night compared with workers who weren’t near windows. [R]
- Psychologically and physiologically unwell hospital patients seem to recover faster when exposed to sunlight. [R] [R] [R] [R] [R]
- In elderly patients with major depressive disorder, bright light therapy improved mood, sleep efficiency, and cortisol levels. [R]
Lights that Mimic Natural Sunlight
Now onto the practical portion of this guide!
What we’re going to try to do here is the following:
- Increase the brightness at eye level to at least 1,000 lux; really, the higher, the better; it should be ambient and comfortable light, ideally coming from overhead.
- Accomplish this using full spectrum high-quality LED lights if possible.
- Include UV and infrared lights to round out the other parts of the spectrum that are missing.
The only way to reliably mimic the visible portion of sunlight is with LEDs. Now you might be thinking, but Derek, LEDs suck. And you’d be right, except they don’t anymore. (kind of)
Historically, LEDs obtained their “cooler” color with the dreaded big blue spike. However, newer LED phosphor technologies have made these classic LED problems a thing of the past.
What we’re left with instead is an impeccably realistic color spectrum, that feels natural and energizing!
Unfortunately, the pickings are rather slim. Hopefully, with time more companies and manufacturers get in on the full spectrum LED game.
The Best Full Spectrum Light Bulbs
The best option in the US right now is Sunsy Shine, a company we started out of frustration with other options.
These offer the best full-spectrum SunLike diodes, flicker-free performance even while dimmed, three great colors to choose from, and we also have a great refund and warranty policy!
Here are the three options and their spectral qualities:
Can’t go wrong here!
Another option is Yuji. This company makes its own sunlight-mimicking bulbs that are also flicker-free and tend to run a bit brighter, although I do prefer the SunLike spectrum.
They’re unfortunately very expensive and the refund policy and warranty policies also aren’t quite as nice if that’s a deciding factor.
Yuji sells A19, BR30, and LED strips in various color temperatures.
A great budget option is the Philips Ultra Definition lineup. The spectrum and flicker are pretty good although they both vary quite a bit across the lineup for some reason.
The red portion is lacking a bit compared to better full spectrum bulbs like Sunsy and Yuji however and you can see the amber/red spike meant to cheat the R9 CRI red score (tisk tisk).
But overall they’re a decent budget choice.
One last recommendation would be the 15w bulb from Sylvania’s Natural Series. This version, in particular, has the best spectrum and flicker of the ones I tested. Just lacking in the red range.
You can check out more of the lights we’ve tested by visiting our database below!
The Ultimate Ceiling String Light
I recently built a giant strong light fixture for about that puts out around 45,000 lumens of full-spectrum, flicker-free light throughout my dining room, living room, and kitchen.
This gives you the ability to spread the light out over a larger surface area, making it less glaring to increase the total lumens in a room.
To create this I bought a white string light fixture with 8 sockets. I recommend white since it blends into the ceiling much better than black.
I attached this to my ceiling with small screw hooks and drilled tiny pilot holes for them.
Then I plugged 8 of these 7-in-1 splitters into my string light fixture so that I could fit 56 lights which is right around the wattage of this string light.
For the bulbs, I went with these Philips Ultra Definition lights. they’re pretty affordable, offer a nice high CRI spectrum that’s fairly natural, and have a low flicker.
For convenience, I bought this RF outlet and mounted the switch on the wall next to my kitchen lights.
It basically feels like a permanent light fixture!
The end result is bright, comfortable, and looks pretty decent actually, not as much of an eyesore as I thought it might be.
This has made a huge difference for us in the winter. Altogether it cost about $300 and has been well worth it.
The DIY Chandelier
Here’s another thing I’ve done…
You can create your own hanging chandelier, the same hooks as above can work here too.
Though more than one would be ideal, we really want to pump those lux numbers up.
You may want about three or four of these in a room to really increase the lumens.
DIY Chandelier
Here is a DIY chandelier using six GE Sun-Filled bulbs and a single 72-watt halogen for infrared coverage. This setup costs about $100 and provides approximately 6370 lumens.
My recommendation now would be to use 5700K Sunsy Shine bulbs instead.
This could be done using any combination of lights.
Parts:
Desk Lighting
Okay, so what about those of you who have a work office and want more light all up in those eyeballs?
Various lamps, extenders, and fixtures can be utilized to provide point-of-use lighting.
These kinds of setups can obviously risk introducing glare, meaning the light source stands out too much from the ambient light, causing discomfort. Getting the lights above eye level and further from your screen helps.
Even just one BR30/40 pointed toward you during the day could have a really positive impact on your mood, sleep, and overall well-being.
I’m currently working on a DIY over-the-monitor glare-free high-lumen desk light that should hopefully be cost-effective and easy to build, I’ll update this section once it’s done!
High Lumens on a Budget
One more option, while not perfect (none of them are really) is to utilize super high lumen output flood lights or high bay lights in your home.
UFO High Bay Lights
Increasing the lumens in living areas dramatically may benefit those suffering from seasonal affective disorders or sleep disorders.
While the light these put out isn’t ideal from a quality standpoint, you likely stand to benefit more from high lumens than high-quality low-lumen light.
I haven’t played around with these personally yet but I plan to buy several soon and test them out so that I can recommend the best ones.
In the meantime, if you have the budget for it Yuji sells basically the only high CRI UFO high bay light I know of:
Yuji 200W High Bay Light

This Yuji light can be ceiling mounted right above your workspace and produces very high-quality light.
It’s flicker-free and dimmable, and you can even get an option motion sensor.
Both 4000K and 5000K versions are available.
Use code OYBYJ5 for 5% off!
You should be able to mount these “upside down” using plant hangers. This will give you a very dispersed ambient light effect without any risk of glare.
Garage Lights
The arms on these lights can be titled to point to the side rather than directly down if you want to create a more ambient light effect.
Similar to the UFO lights, I haven’t gotten my hands on a sufficient number of these to find the best ones yet.
Mimicking Full Spectrum Infrared Light
The next step in our replication of sunlight is to bring infrared back into the game.
Infrared light is of course very famous right now as red light therapy and is useful for a number of reasons. However, most of us go entire days without getting any IRA or B on our skin, and that is just no bueno.
The Science Behind Full Spectrum Infrared Light
Why is infrared light so beneficial and necessary?
- Red and infrared radiation penetrates the deepest into the body and helps mitigate the stress response from short wavelength blue, violet, and UV exposure. [R]
- Morning exposure to red light improves eyesight in older people, afternoon exposure however did not seem to have the same effect. [R]
One of the best ways to introduce infrared into your environment is with tungsten filament lights.
Technically, the Sun contains a quite bit more IR-A than IR-B and very little IR-C. While tungsten filament bulbs contain proportionately more IR-B and IR-C than the sun.
Now, this graph is now completely accurate, because halogen bulbs actually burn hotter than regular incandescent and thus emit more visible light, hence their more “efficient” label.
Check out the difference between an incandescent and a halogen at around the same wattage:


You can see that the halogen gas allows the halogen bulb to run a bit hotter, and thus emit more visible light at the same wattage.
The image below shows the general curve trend of sunlight compared to one of these tungsten filament lamps.

What the image above is missing is the absorption bands of water. Because as sunlight passes through the atmosphere, water droplets in the air absorb much of the infrared.

So, if you want to get really nerdy, you have to filter your infrared with water. What you’re left with is called wIRA or water-filtered infrared A.
This kind of infrared is used medically in devices like the HydroSun, as the smaller amounts of IR-B and IR-C prevent the skin from overheating, and allow for higher doses of IR-A which penetrate much deeper into the skin.
It’s basically impossible to purchase such a wIRA device at this time, so I’m trying to figure out how to make an easy-to-build DIY device.
Once I have something to report on that, you’ll be the first to know!
If you sign up for my newsletter that is.
But for now, I think regular old halogen is gonna be okay.
Strategies for Infrared Coverage
Here are a few ideas for you to try out and customize to your spaces.
For larger areas, and for a bit more throw, you can use high-wattage heat lamps.
After having this setup for about a year, I love it!
And if you’re looking for a good general-purpose infrared bulb to include in your visible light setups, grab a 72w halogen. These probably won’t be around much longer due to changing energy laws get them while you can!
Mimicking the Ultraviolet Spectrum
Finally, we have ultraviolet light, and yes, it too is an important part of sunlight! Believe it or not, both UVA and UVB penetrate the atmosphere all year, even in high-latitude areas in the winter.
The reason it’s often said that you can’t make vitamin D in the winter is just that there’s much less UVB, and you’re always wearing clothes. But it’s still there.
The Science Behind Ultraviolet Light
Our bodies have adapted to utilizing UV radiation for a very long time.
We of course need UVB and UVA to make vitamin D in the skin, as well as some other things, so I think it’s a good bit of common sense to put a healthy amount of UV in our homes.
As I mentioned earlier in the guide, natural sunlight gets as strong as around 20:1 UVA to UVB, so we’ll want to try to match that the best we can.
The Best Ultraviolet Lights
The best UV lights are currently fluorescent in nature, LEDs that produce wide-spectrum UV are recently gaining a bit in the reptile space, so it might not be too long before we see decent LED options, they just aren’t here yet.
And so fluorescent it is.
Fluorescent lights contain trace amounts of mercury and other toxic metals. Be careful not to break them, and if you have children who throw things, you may want to purchase a cage for your light.
Safety Warning
- Arcadia 6% UVB Lamp: This is probably one of the best UV lighting options out there currently. It provides a ratio of 5:1, which clearly isn’t 20:1, but at a low UV index I don’t really see this being a huge deal, I would certainly consider it better than no UV at all. The ballast used in the Pro T5 Kit is a high-frequency electronic ballast, so there’s no flicker and very low EMF exposure, unlike the old magnetic ballasts some of you may be familiar with.
How to Implement
The best way I know of to add ultraviolet into your indoor space is by mounting a T5HO tube lamp in the corner of a room’s ceiling.
These can be added to any number of rooms where large amounts of time are spent.
TIP: Fluorescent UV bulbs should be replaced every year or so, as the UV output fades with use.

The UV index for this light setup is as follows:
1 ft: 3.5 UVI
2 ft: 1.5 UVI
3 ft: 0.8 UVI
4 ft: 0.5 UVI
5 ft: 0.2 UVI
Measuring Light
Here’s a collection of various tools for measuring your light environment, before moving forward, you may want one or two of these.
- Opple Light Master Pro 3: This little thing is unbelievable for the price! If you want to test your own lights look no further! This will give you lux, color rendering index (CRI), flicker, color temperature (CCT), and more! All for less than $50, crazy awesome device.
- Solarmeter Model 6.5 UV Index Meter: You’ll probably want one of these if you plan to incorporate a UV bulb into your sunlight spectrum setup. This way, you can ensure you won’t be exposed to unnaturally high levels of radiation.
- Handheld Digital Light Meter: This is a fun tool to have on hand if you’re looking to emulate the brightness of the sunlight in your area. It’s also just a fun tool for curious-minded folks.
TLDR: Action Steps
This section is for those of you who either don’t have time to connect all the dots above or just want a quick list of things that can be done to optimize your biology.
- Ensure that the indoor environments in which you spend the most time have adequate circadian light, i.e. >500 total lux, ideally >1000 lux. This can be done with any lux meter.
- Purchase full spectrum LED light bulbs of 5000K or greater for daytime use in your home and office, and purchase or create fixtures that will allow you to achieve a high level of lux. NorbSmile is a great option.
- Set up full-spectrum infrared lighting by using either incandescent heat lamps or BR30/A19 halogen bulbs.
- Bring healthy UV into your space by mounting a reptile T5 fluorescent light in your most occupied area(s).
Hi Derek — love your site. Can you clarify what times of day UVB overhead lighting should be used? And should it be well above sight line in the upper corner of a wall or is it OK if it’s above a row of windows? Since implementing all these suggestions, I definitely notice more energy & better mood — BUT — my deep sleep has tanked (Oura ring). Thanks!
Oura sleep staging is at least useful for trend analysis so it’s interesting that you’ve noticed a change like that! So you’re saying subjectively you feel better? If that’s the case I wouldn’t be worried, perhaps you simply don’t require as much deep sleep? How about the others like REM or awakenings, any trend change there?
As for the UVB, I’d say between 10am and 4pm would be a reasonable time frame?