Sleeping With the Window Open: Fresh Air, Noise and When to Close It

Sleeping with the window open can mean fresher air and a cooler room, and there's some research suggesting it may help your sleep. It can also let in traffic noise, early light, pollen and the odd mosquito. This guide covers what happens to bedroom air overnight, what the evidence says about open windows and sleep, the trade-offs, when to keep the window shut, and how to get fresh air without the downsides.

The short answer: for many people, sleeping with the window open is a good idea when it's safe and the air outside is cooler and quiet enough. A closed bedroom builds up carbon dioxide overnight, and a small Dutch study found people reported deeper sleep with a window or door open. The Sleep Health Foundation notes an open window can help cool the room as the night cools. Keep it shut if noise, smoke, pollen or security is a problem, and use other ways to ventilate instead.

What happens to bedroom air overnight

Every breath you breathe out adds carbon dioxide (CO2) to the room. In a small, closed bedroom, especially with two people, the level climbs through the night, and it's a useful sign of how stale the air is.

In a study of 17 healthy young adults in the Netherlands, researchers measured bedroom CO2, temperature and humidity over five nights. The average CO2 level was about 717 ppm with a window or bedroom door open, and about 1,150 ppm with both closed. The temperature barely changed between the two set-ups (Mishra and colleagues, Indoor Air, 2018).

Does an open window help you sleep?

In that same study, people rated their sleep as deeper on the open nights, and wrist-worn activity monitors showed differences in sleep between the two conditions. It was a small study in healthy young adults, so it's a hint, not proof.

The clearer benefit in Australia is often temperature. The Sleep Health Foundation says the ideal sleeping temperature is around 17 to 19°C, that air flowing over your skin helps cool your body, and that an open window can help circulate the air as it cools overnight (source). Healthdirect gives similar hot-weather advice: keep curtains and blinds shut during the day, then open windows and doors to let the house cool once the heat passes (source).

Window open or closed: the trade-offs

Factor	Window open	Window closed
Fresh air	Lower CO2, less stuffy	CO2 builds up overnight
Temperature	Cooler once outside air drops	Holds heat on warm nights, holds warmth on cold nights
Noise	Traffic, neighbours, birds at dawn	Quieter
Light	Street lights, early sunrise if curtains move	Easier to keep dark
Pollen and smoke	Lets them in	Keeps most out
Security	A risk on ground floors	Secure
Insects	Needs a flyscreen	No issue

Noise is the big one for light sleepers. The World Health Organization recommends less than 30 dB(A) in bedrooms at night for good-quality sleep (source). A window facing a busy road can easily let in more than that. If noise is your problem, see noisy neighbours sleep tips and light sleeper tips.

When to keep the window shut

• Bushfire smoke. Healthdirect advises staying indoors with windows and doors closed, preferably with air conditioning, when smoke is around (source).
• High pollen days if you have hay fever or asthma. In Victoria, the grass pollen season runs from October to December, and people with both asthma and hay fever face the highest risk from thunderstorm asthma (source). See hay fever and sleep.
• Hot, humid nights when the outside air isn't cooler than inside. Opening up just lets more heat in.
• Ground-floor or easy-access windows. Use a window lock that allows a small gap, or ventilate another way.
• Loud nights, such as roadworks or a party next door.

Ways to get fresh air without the downsides

1. Open the bedroom door instead. In the Dutch study, an open internal door counted as an open condition and also lowered CO2.
2. Open a window in another room and leave doors open so air moves through the house.
3. Open it a crack. A small gap with a lockable stop is better than nothing.
4. Air the room before bed. Open up for half an hour in the evening, then close it if noise or security is an issue.
5. Fit flyscreens and use heavy curtains or blinds so the early sunrise doesn't wake you. See how dark should your bedroom be.
6. Use a fan to move air. See sleeping with a fan on.

When to see your GP

If you wake with headaches, a blocked nose or wheezing most mornings, or you're tired despite a fresh, cool room, talk to your GP. Morning headaches can have several causes; see waking up with a headache. If you have asthma, follow your asthma action plan and call triple zero (000) in an emergency. This guide is general information, not medical advice.

Where the Sovune Nudge fits

We make the Sovune Nudge, a vibrating alarm wristband, so we're not neutral. With the window open, outside noise and early birds can mask a quiet alarm, and a loud one carries next door. A wrist alarm wakes you without either problem.

• Silent. No speaker and no sound, so your alarm doesn't drift out the window to the neighbours.
• Wakes you with vibration on your wrist, starting as a gentle tap and building through three intensity levels.
• No light in the room except a small display that lights when you press the button, which suits a dark bedroom.
• Three separate alarms, set on the band itself with no app or phone.

It comes with a 30-day money-back guarantee.

Quick answers

Is it healthier to sleep with the window open? It often means lower CO2 and a cooler room, and one small study found people reported deeper sleep. It isn't better if it lets in smoke, pollen or loud noise.

Should I sleep with the window open in winter? You can open it a crack for fresh air with warmer bedding, or open the bedroom door instead. There's no need to make the room uncomfortably cold.

Is an open door as good as an open window? In the Dutch study, an open bedroom door also lowered CO2 compared with a closed room, so it's a useful option when the window has to stay shut.

Can I sleep with the window open if I have hay fever? On high pollen or windy, stormy days in spring, it's safer to keep it shut. Ventilate when pollen counts are lower.

For every type of silent alarm compared, see our complete guide to vibrating alarms in Australia.

See the Sovune Nudge →