Darkness

There is one luxury the finest suite on earth cannot promise you, and it happens to be free. Darkness. Not dimness, not blackout curtains drawn over a glowing city, but true darkness, the kind that once came to every bedroom and now costs a fortune to get back.

We lost it so gradually that almost nobody noticed. A street lamp went up outside. A television took its place at the foot of the bed and kept a small red eye open all night. Chargers, routers, air purifiers, a clock, a smoke alarm, each one arriving with a light on it because a light is cheap to add and looks like proof the thing is working. None of it was a decision. The modern bedroom simply glows, faintly, all night long, and we have grown so used to it that a genuinely dark room now feels strange for the first few nights.

The body never got used to it at all.

What a single night of light actually does

The body reads even a little light as a small emergency. That sounds like a figure of speech and it is not.

Researchers at Northwestern put healthy young adults to bed for two nights. The first night everyone slept in a properly dim room, under 3 lux. On the second night, half of them slept in a room lit to 100 lux, roughly an overhead light left on in a hallway, nothing anyone would call bright. They stayed asleep. They did not report being disturbed. By most outward measures the night looked fine.

Inside, it was not. Their heart rate ran higher all night long, and the nervous system stayed in its daytime setting through the hours it is meant to stand down. By the following morning they handled a sugary drink noticeably worse than the ones who had slept in the dark: more insulin needed for the same job, on the back of one single night.

The number is the part worth holding on to. 100 lux is less than you are reading this by. A living room in the evening runs about that. An office runs three to five times higher. The room in that study was not lit up, it was merely not dark, and merely not dark was enough to move the needle on heart rate and blood sugar in a single night.

One study is one study, and this one was small and short. But it points the same way as everything else we know about the eye and the clock, and it has the great advantage of being cheap to act on. There is no risk in a dark bedroom.

Why dimness is not darkness

There is a set of cells at the back of the eye whose only job is to report on light. They are not there for seeing. They are there for timing, and they answer to brightness and to blue, which is precisely what a standby light, a phone screen and a street lamp are made of. They keep reporting through closed eyelids, because an eyelid is thin and light passes through it.

This is why the room matters more than the intention. You can be deeply asleep and your body can still be filing hourly reports on the light in the room, and adjusting itself accordingly. Nothing about that requires you to notice.

Which is also the good news. If the room is dark, the reports stop, and everything downstream settles by itself. You do not have to do anything clever.

What the grand hotels are selling

The best hotels in the world worked this out some time ago, and priced it accordingly. There are now suites built entirely around a single good night, sold at past $1,000 a night, and the room is genuinely excellent. Sealed light, honest air, a bed you would happily be buried in.

But look at what is actually being sold. Strip out the marble and the turndown service and the working ingredient is an absence: no light, no noise, no fumes, nothing arriving. It is the only luxury product I know of that is made entirely of things being taken away, which is exactly why you can have most of it at home for the price of a roll of tape.

The edge here is aimed at the pricing, not at the hotels. They did the hard thinking and they built the rooms properly. It is just worth naming what you are paying for, because at home the same thing is nearly free.

How to make a bedroom genuinely dark

In the order that gets you the most darkness for the least effort and money.

• Kill the small lights first. Walk into the bedroom at night, stand still for a full minute until your eyes adjust, and count every glowing thing. Most people find between four and nine. Unplug what can be unplugged, and put a strip of black electrical tape over the rest. This costs nothing and it is the single biggest step.
• Close the seam. Blackout curtains almost always leak down the middle, where the two panels meet, and around the edges. Overlap the panels and clip them shut, or fit the rail wider and higher than the window so the fabric falls past it on every side. The curtains I would actually buy, and the plastic-lined ones I would not, are in the blackout group of the Hearth directory.
• Deal with the door. A lit hallway pushes a surprising blade of light under the door. A rolled towel or a draught excluder ends it in ten seconds.
• Move the phone out of the room. Not only for the light. It also removes the temptation that keeps you up, and it forces you to own a real alarm clock, which is a pleasure in itself. Choose one without a permanently lit face.
• Deal with the street last. This is the expensive one, so leave it until the free steps are done. Often a second heavier layer behind the existing curtain is enough, and costs a fraction of a fitted blind.
• A good sleep mask is the fallback. Not as good as a dark room, because light still reaches you at the edges, but far better than nothing and the only real option in a hotel or on a train.

The test is simple. Get into bed, turn everything off, and wait ten minutes. Then hold your hand in front of your face. If you can see it, the room is not dark yet, and something in it is still reporting to your nervous system on your behalf.

Give it a fortnight

The first two or three nights in a properly dark room can feel oddly empty, the way a quiet house feels after the fridge stops humming. That passes quickly. What most people notice by the second week is not dramatic sleep, it is the morning: waking a little before the alarm, and the first hour of the day arriving with less friction in it.

That is the whole of it. No device, no subscription, no protocol. Darkness is one of six principles I hold the whole house to, and the rest of them are in The Hearth. The companion pieces, on the air in a closed room and the temperature of it, are the other half of a good night.

Darkness is the oldest and grandest luxury there is, and the bill never comes.