Night AirThe room above the bed
Almost all sleep advice concerns the bed, and almost none of it concerns the air, light and sound of the room around it, which is where a sleeper spends every one of those eight hours.
Five conditions of a room
All five topicsAir and ventilation
Carbon dioxide in a shut room, the trade against noise, and what opening a window in winter costs in heat.
02Thermal
The overnight curve, bedding as insulation, and why a set point is not a temperature.
03Moisture
Humidity through a closed-door night, condensation, and the dust mite threshold.
04Volatiles
Off-gassing from new mattresses and furnishings, and what a home VOC monitor can and cannot tell you.
05Light and sound
Light at the pillow, blackout curtains and shades, and masking sound.
Guides
Every guide
Does white noise help you sleep, and how should you set it up?
Most people reach for white noise because of something outside the bedroom: a bus route, a shared wall, a partner on a different schedule. The research answers a narrower question than the marketing does, and the useful part of that answer covers volume, placement, and the sound you are covering.
How do you ventilate a bedroom in winter without losing the heat?
On a cold night a closed bedroom stays warm by giving up its fresh air. Two people breathing for eight hours in a small sealed room can push carbon dioxide well past the level that sleep researchers now link to worse sleep. The fix is a small, steady flow of outdoor air, sized to the number of sleepers and warmed on its way in.
What is the ideal humidity for a bedroom?
Relative humidity compares the water vapor in the air with the most that air could hold at its current temperature. It is the number a hygrometer shows. For a bedroom, the EPA says indoor relative humidity should stay below 60 percent, ideally between 30 and 50 percent (EPA, Mold Course Chapter 2). A 1986 health review argued for 40 to 60 instead (Arundel et al., 1986). This page explains why the two differ and gives a working number for each season.
How do you read a VOC reading, and what does a new mattress emit?
A home VOC monitor gives you one number for a mix of many gases, and the low-cost sensors in most units cannot turn that mix into a true concentration. Lab work fills in the other half. In a University of Texas study, new crib mattresses released about four times as many VOCs as old crib mattresses (UT Austin). The same study found that mean total VOC emission rates were 56 μg/m2h at 23 °C and 139 μg/m2h at 36 °C, which is 73°F against 97°F (Boor et al., 2014).
Does your body temperature rise when you sleep?
At night two parts of the body move in opposite directions, so this question gets two different answers online. The core cools from the evening on, while the hands and feet warm by about 1°C, just under two degrees Fahrenheit, around the moment of falling asleep, and that skin warming is how the core gets rid of its heat (smart bed skin temperature study).
Which blackout shades keep a bedroom dark at night?
A blackout shade should keep a bedroom dark whether the light outside comes from a streetlamp, a neighbor's porch light or an early summer sunrise. Most blackout fabrics stop nearly all the light that hits them, going by the seller pages counted below, so fit around the window usually decides how dark the bedroom gets.
Room check
Six questions that point to the likeliest cause of a bad night in the room.
About this publication
What does a bedroom do to a sleeper overnight?
A closed bedroom changes across a night: the air cools or warms, humidity and carbon dioxide build, and light and sound arrive on their own schedule.
Outdoor air keeps cooling toward a low near dawn, a shut room holds the moisture and carbon dioxide of everyone breathing in it, and street light and early sun reach the bed whether anyone is awake or not. None of this is visible from the pillow, and most of it can be checked with an inexpensive meter.
This publication collects what published research, health agencies and building science say about those conditions, and what that means for a person trying to sleep.
Which conditions are worth checking at home?
Five: air temperature at the pillow, relative humidity, carbon dioxide in a shut room, light at the pillow, and the noise events that wake people.
The overnight curve rather than the thermostat setting, and the ranges health services publish.
What a closed door does across eight hours, where condensation starts, and the band agencies advise.
How carbon dioxide builds in a shut bedroom and what ventilation research says about it.
Light at the pillow before dawn, and the noise peaks that wake a sleeper.
How does this site reach its figures?
By reading published studies and agency guidance, and by counting what sources state. No instrument has been run in any room for this site.
Every figure is linked to the page it came from, in the sentence that uses it, so any number can be checked against its source. Where a common claim about bedroom air turns out to be unsupported, the page says so in the sentence that carries the claim. The method page sets out the rules.