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How to fix your indoor lighting to simulate sunlight

Upgrading your lighting is one of the most impactful purchases you can make to improve quality of life during the winter.

Shamay Agaron
Shamay Agaron
. 7 min read

I’ve always been someone who's hated the winter months, which I thought was mostly because of the cold. With the shift to working from home though, I’ve increasingly been noticing how hard it is for me to focus after it gets dark outside (as early as 4:30pm in NYC).

I finally decided to buy bright lights for my room to better simulate daylight, and the effect was really dramatic. Instead of having a strong urge to stop working whenever it got dark out, I was suddenly able to maintain my normal summer schedule and keep working until dinner.

I’m going to make the case that upgrading your lighting is one of the most impactful purchases you can make to improve quality of life during the winter months.

Light suppresses melatonin release

Studies have shown that sufficient light exposure in the evening time is associated with increased subjective alertness and mood, primarily by suppressing melatonin.

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If you don’t have bright enough indoor lighting in the winter, then your body essentially sends the signal to get ready for sleep after the sun goes down at 4:30.

This means that you're needlessly fighting with your own body by trying to power through and continue working. During the summer, your body is exposed to natural light until much later in the day and so the melatonin signal is delayed until 7 or 8.

The idea is to use artificial lights to simulate daylight in those 3-4 hours, so that you’re essentially on your summer schedule all year.

Light deprivation affects everyone

One reason for indoor lighting being commonly overlooked is that most of the content around lighting is written for people who suffer from seasonal affective disorder (SAD).

While some people do have crippling winter depression when there’s not enough natural light, it’s safe to say that almost everyone is affected by light deprivation to some degree. Light exposure is the most important driving force behind your circadian clock, which has downstream effects on your alertness, mood, hunger, sleep, and most other bodily systems.

Knowing this, it doesn’t make much sense to characterize SAD as a discrete condition that you either have or don’t have. A better way of looking at how people respond to light is a spectrum, with SAD on the tail end of the curve in terms of debilitating symptoms.

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I usually feel much more lethargic and deflated in the winter time, but it took me a while to make the connection to light deprivation because my symptoms never seemed “that bad”.

We’re terrible at estimating light intensity

To get a better sense of my light exposure at different times of day, I installed a light meter app that reads out the brightness in lux (unit of ambient brightness). It turns out that I get anywhere from 1,000 to 3,000 lux through my window during the day and just 100 to 300 lux after sunset from the lighting in my room.

Without the light meter app, I would never have noticed that I get 10 times less light after sunset in the winter months. Dr. Samer Hattar says this is because our visual system is not good at estimating light intensity consciously. The cone receptors in our eyes have an incredible ability to adapt to different conditions, but it comes at the cost of conscious awareness of light intensity.

With this in mind, it makes sense that people usually don’t notice poor lighting conditions. This is also why it’s so hard to make the connection between light exposure and alertness.

To give a few more reference points – a cloudy day is about 1,000 lux, a sunny day in the shade is about 10,000 lux, and direct sunlight at noon is about 100,000 lux. It’s hard to believe these numbers, but direct sunlight really is 100x brighter than a cloudy day and 1000x brighter than the average indoor lighting setup.

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It’s no wonder that people feel lethargic on cloudy days and in the winter months, when we spend more time indoors. Chances are that your indoor lighting is nowhere close to simulating the natural light that you usually get through your window in the summer months.

Setting your circadian clock in the morning

Before jumping into designing your indoor lighting – a brief aside on morning light exposure.

I’ve previously written about Dr. Andrew Huberman, who stresses the importance of getting 15-30 minutes of direct sunlight in the morning to set your circadian clock. Now that we’ve established that light coming in through a window is roughly 50 times less bright than sunlight, it’s clear why you it's crucial to go outside.

If natural light is not possible, whether because you wake up before sunrise or you’re not willing to brace the cold, consider using a light therapy lamp. This is not in the scope of this post, so please refer to Dr. Scott Sisskind’s thorough guide for details on light therapy.

Now back to the main thread.

Designing your indoor lighting

My goal with the lighting in my room was to simulate the brightness of the natural light that would normally be coming in through the window between the hours of 4-7pm in the summer. That way, there wouldn’t be a sudden loss of alertness when the sun set early in the winter.

I wanted to stress that you should turn off the lights at least 3 hours before bed. Having bright lighting will keep you from going to sleep and negatively impact your health if not used carefully.

With that out of the way, what are the main considerations in designing your indoor lighting?

Placement

As a general rule, it’s better to illuminate the whole space evenly rather than just the corner of the room where you’re sitting. This is because the photoreceptors that you’re trying to activate cover your entire retina, so you want to illuminate your full visual field if possible.

Since we’re going for bright lighting, you definitely don’t want it in your direct line of sight. Placing the lights high on the wall or on the ceiling are the most common locations, both of which mimics the angle at which the sun usually hits your eyes.

Brightness

The brightness of lights is measured in lumens. This is not the same as lux, which is the measure of how much light you actually get in your eyes (lumens per area). In other words, you get less light as you move further away from the source.

The goal when designing indoor lighting is to create a certain amount of lux, preferably at least 1000 lux over the full room. To calculate how many lumens you need to light your space, this calculator is pretty helpful.

In my case, it recommended around 5,000 lumens to properly light an 80 square foot room with office-level brightness. Note that you will likely need at least a few bulbs that add up to the total number of lumens, because just one will not be bright enough.

Light color

The color of the light is called the color temperature, which it’s measured in Kelvins (K). The color temperature of sunlight changes dramatically during the course of the day, and so should the temperature of your indoor lighting. Direct sunlight at noon is between 5000K - 5600K (white light) whereas around sunrise or sunset it’s closer to 2700K - 3500K (yellow light).

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It’s important to design the evening to look different from the workday, especially if your bedroom doubles up as your work room. This means that you need “cool” 5000K lights during the day when you’re working and “warm” 2700K lights at night when you’re trying to wind down.

Some lights offer color temperature controls, which is very convenient because you can change them at different times of day.

Color Rendering Index (CRI)

The color rendering index (CRI) is a measure of how well-balanced the different wavelengths of light are compared to sunlight. You can think of the CRI value as a percentage out of 100. It’s best to aim for a CRI of 90 or higher. It’s best not to go lower than 80, because the lighting looks pretty sterile and sickly otherwise.

Sometimes this is marketed as “full-spectrum” or “broad-spectrum” light.

General recommendations on what to buy

Everyone’s spaces are built differently, so I’ll try to cover different setups.

On a high level, you usually want to buy LED lights for their high CRI, efficiency, and lifespan. A simple option is to buy a few 1600-lumen 5000K Cree bulbs paired with a light socket splitter.

If you don’t already have fixtures to hang the lights, you could buy a light socket cable that supports multiple bulbs and hang it on hooks or a curtain rod mounted on your wall or ceiling. You could also use photography stands and them with fake ivy to make them look a little better.

If your desk supports a clamp, you could invest in a tall, ultra-bright desk lamp (cheaper alternative) that sits above eye level. I’ve also been experimenting with desk-mounted LED panels that are meant for photography or streaming (super high CRI and brightness), but they don't illuminate the room evenly.

(sorry for the mess)

For nighttime bulbs, there are more options because you need far less lumens and it’s much easier to find high CRI, low temperature (<3000K) bulbs. Potentially optimize for dimmability?

Summary

I hope this has been useful. The most important things to remember are:

  • get at least 1,000 lux over the full room (calculator)
  • white (>5000K) lights with 80+ CRI during the day
  • switch to yellow (<3000K) lights at least 3 hours before bed
  • try to cover your whole visual field, without directly looking at the lights

Let me know what you think! I’d love to hear about people’s experiences with designing their indoor lighting.

I wanted to acknowledge Richard Korzekwa's article as well as Ben Kuhn's post, both of which I've borrowed ideas from.