How to walk upright and stop living in a cave

Call me arrogant, but I’d rather optimize my indoor environment than try to spend more time in the capricious outdoors. I think it’s defeatism to give up on improving our indoor spaces and resign ourselves to the fickle weather and seasons.

If I was going to create an ideal environment for a human, I think there are several things I would include that we routinely fail to include in our homes and offices.


Our indoor lighting situation usually sucks. The fact that “natural lighting” is a selling point in real estate shows how terrible a job we are doing in this department. We rely on the sun naturally providing us with sufficient light, and if it’s an overcast day or the days have grown shorter in the winter, then I guess we’re shit out of luck.

Usually, indoor areas are around 50-500 lux. This is hundreds of times dimmer than the sunlight. Clearly, we weren’t designed to thrive in such dim environments, and science does verify a connection between brighter light and alertness. If we don’t want to be sleepy like it’s nighttime, we shouldn’t light our rooms like it’s nighttime. For some, the effects of dim lighting go beyond simple lethargy and, especially in the winter, cause serious mood problems like seasonal affective disorder or the winter blues. This is common, but it’s not necessary. Bright light, particularly blue light, can also generally boost mood and may be a comparable stimulant to caffeine. (Those who are prone to mania should be careful, as intense light can trigger mania or hypomania in those predisposed.) Brighter lighting can also help circadian rhythm issues (which I, for example, have struggled with for years), both by entraining your circadian rhythm so your body better knows when it’s day, and by shortening it if it’s too long.

Lighting isn’t as expensive as it used to be, so we can do better than we have in the past. The cost of electricity for LED lighting is now negligible, and the only real factor is the cost of the bulbs themselves. Reaching for the full 100,000 lux of sunlight would still be prohibitively expensive, but going for at least 10,000 lux is doable with only a few hundred dollars. I won’t go into specifics here, but you can get more information on specific lighting setups here or here. In particular, get bulbs with a color temperature close to sunlight (5600k), but make sure the bulbs have a good Color Rendering Index (CRI), otherwise the light will feel harsh.

I recommend putting any bright lighting you buy for your home on electrical timers so you don’t accidentally leave them on during the evening and screw up your sleep. You may also want to set your phone/computer brightness on a timer, if you can. The goal is to mimic the natural day/night cycle of our evolutionary environment, but without all the pesky volatility of nature. You can get programs like f.lux too, which reduce the amount of blue light emitted by your device in the evening, but in my experience this isn’t good enough and reducing the actual brightness of the device at night is also important.

“But what about vitamin D? Just go outside!” This is terrible advice, and I hear it too often. Sunlight is a powerful carcinogen, and vitamin D supplements are not, and they’re cheap.

Carbon dioxide

Carbon MON-oxide is the deadly one you probably already have a monitor for in your house. Carbon DI-oxide is the feeble cousin of carbon monoxide, but it still has a negative effect on human health: high (but common) levels impairs our ability to think. Just what you don’t want in an office. High levels may also have a negative long-term impact in other areas of our health.

Hold your breath. When it sucks and you decide to start breathing again, it’s carbon dioxide buildup, not lack of oxygen, causing you to feel panic and the need to breath. Carbon dioxide is a toxin. And we breath it out into poorly ventilated rooms, where the levels can rise to double or triple what they are outdoors.

Several studies have shown significant (temporary) cognitive impairments due to carbon dioxide levels over 1,000 ppm, but such levels are common in poorly ventilated shared spaces. Fortunately, the solution is simple: open a window. Unfortunately, this doesn’t work when it’s raining, or when it’s too hot outside, or when it’s too cold outside… In particular, I have to contend with Canadian winters, which means opening the window is a valid strategy for a minority of the year unless I buy an expensive heat recovery ventilator. I don’t have a good solution for mitigating carbon dioxide buildup in the winter. Let me know if you do.

And, by the way, plants won’t work. They won’t suck up nearly enough carbon dioxide. You would need hundreds of plants per person, or roughly a dozen full-size trees per person, to offset the carbon dioxide exhaled by humans in a room.

A fun fact: if we don’t stop pumping carbon dioxide into the atmosphere, then in about a century, carbon dioxide outdoors may reach cognitively impairing levels. Then what do we do?

Temperature and Humidity

High/low humidity and high/low temperature both lead to discomfort and lower scores on concentration measures. People generally have temperature under control, or at least it’s something they’re aware of. Humidity is less common to measure, but a $10 hygrometer should help you get your indoor space to the ideal 30-50% humidity range if it isn’t already. Air conditioners also tend to reduce humidity as well as temperature, so air-condition in the summer and use a humidifier in the winter.

At night, drop the temperature a few degrees if you can; It’s easier to sleep in a cool room. I wonder how many hours of sleep have been reclaimed already due to the advent of smart thermostats.

Background Noise

I imagine this factor is more subjective than the others, but too loud is distracting, even aggrivating; too quiet makes your sniffles and sighs painfully audible to others, and so is distracting. Uneven background noise like traffic is worse than the uniform background noise of white noise or trickling water. Bad background noise leads to poorer cognition and focus.

It’s easy to be bothered by noise and not realize it until the noise stops and a wave of relief finally makes you aware of how annoyed you were by the sound. Noise issues are happily easy to control: earplugs or noise-cancelling headphones will generally do the trick. It would be utopic to eliminate bothersome noise from the environment altogether, but it’s not necessary.

Segregation of Activities

A heroin addict who normally takes their dose in their car decides one day to inject in their bathroom. They die of an overdose, even though they took the same amount they normally do. Why? Our brains maintain associations with different environments. If you normally inject heroin when you get in your car, then your body starts to prepare you for the drug as soon as you get in the car. Drug tolerance, then, is partly environmental. (This actually happened and happens regularly.) Your mind and body are affected by your environment due to Pavlovian conditioning. When the bell rings, the dog salivates. When the lunch bell rings, so do you.

One common piece of advice given by doctors to insomniacs is to only use your bed for sleeping and for sex, and it’s good advice. If you use your bed for reading, studying, and watching TV, then your mind will not form a strong association between the bed and sleep, and you will have a harder time falling asleep.

Likewise, if you do all your slacking off at the same desk you do your work at, you will probably have a harder time focusing. Even having your smartphone within your field of view while you work has been shown to reduce focus. So it wouldn’t hurt to have different areas for work and play, and to not eat at your desk. (And even different user accounts on your computer for work and non-work, if you don’t find that idea to be a pain in the ass like I do.)

We also form associations not just with space, but with time. Hence another piece of common sleep hygeine advice: go to sleep at the same time every night. Your body will learn to expect sleep at that time. Likewise, people who eat at the same time every day eat with their bodies prepared to receive food, and so are less likely to become obese. Studies have shown this. Unfortunately, setting every aspect of your life to a clock can make you feel like a robot, so I usually don’t tolerate such rigidity in my life. But it’s worth thinking about.


  • Brighter lights for your poor eyes
  • Better ventilation for your poor lungs
  • Optimal temperature and humidity for your poor skin
  • Less distracting background noise for your poor ears
  • Activity-specific areas for your poor brain

I also think the aesthetics of most of our indoor environments could use an upgrade, but I don’t have much to say on the subject besides simply saying so. (Though I would bet: green lush > grey drab.)

We sometimes act like we are just machines, but we are not. We’re mushy creatures with delicate bodies and delicate minds, too. And we evolved for one specific environment. There is no guarantee that the indoor environment which is cheapest to produce is going to be just as good for us as a bespoke imitation of our evolutionary environment, and in fact it is not. I think life would be more pleasant if people took these factors more serously when designing indoor environments, and our work would be more efficient and less prone to mistakes.

Published 28 October 2020