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Sleep with the window open: What’s in favour & what’s against?

A lot of people sleep with their windows open at night – even when the temperatures drop to or even below zero in winter. But is an open window at night really healthy for the immune system? And what is the argument against sleeping with an open window? We’ll tell you about the pros and cons you should consider when you stand in front of your window in the evening and ask yourself: window open or closed?

by CALIDA

15 September 2023 • 6 min reading time

Sun shines through the open window in the morning

Sleep with the window open: health risk or benefit?

Advantages of sleeping with the window open

Many people claim that they can only sleep with the window open. Surely, this behaviour can be a kind of habit. Especially in summer, however, it may actually be the case that an opened window contributes to restful sleep. The improved indoor climate and the falling temperatures at night are primarily responsible for this.

Cooling down in summer

If you can’t sleep at night, toss and turn, push aside the blanket and sweat, you should take a look at the temperature in the bedroom. Scientists have found that a temperature between 16 and 18 °C is ideal for sleeping at night. In summer, these temperatures are often utopian. It’s not uncommon for attic dwellers in particular to spend their nights in bedrooms that are more than 23 °C warm.

No wonder that the window stays open at night! In addition to open windows, there are several things you can do to keep the temperature in your bedroom in check. While air conditioning consumes a lot of electricity and does not necessarily improve the air quality, proper ventilation should be in place, especially during the day. A regular exchange of air and darkening the room from the moment the temperature rises ensure a consistently pleasant temperature in the bedroom.

Fresh air & pleasant indoor climate

Depending on where you live, the fresh air from outside can also contribute to the quality of sleep. Especially in the countryside or in quiet areas with little road traffic, you benefit from the purity and freshness of the air. The indoor climate improves, you can sleep more comfortably and breathe easier.

In big cities and along major roads, however, the air quality and the noise are anything but healthy or even conductive to your sleep. What else speaks against sleeping with the window open, you’ll find out now.

Disadvantages of an open window at night

For some, leaving the window open at night, especially in summer, is the only solution to regulate the temperature in the bedroom. Nevertheless, there are some points that speak against an open window at night.

Noise from road traffic, dogs or neighbours

We already touched on the fact that loudness can affect sleep. In fact, living on a main road can have a strong impact on the psyche. Because while we sleep, our brain processes dog barking, noisy neighbours, and the sounds of every single passing car. In the process, it releases stress hormones that can lead to depression in the long term in sensitive people or in an extreme noise environment. An open window amplifies these noises and can thus disturb your sleep and your wellbeing in the long term.

Poor sleep due to freezing at night

Many people claim that you should not sleep with the window open when you have a cold. This is a half-truth that depends mainly on the room temperature that prevails in the bedroom at night. With a blanket, you are wrapped up warm enough at night, even at a temperature of 16 °C. We hardly ever reach such low values in spring and summer anyway.

If you already caught a cold and left the window open in cold autumn and winter nights, you may be slower to get rid of the flu. Because while you are cold and your body is busy keeping warm, it can fight pathogens less effectively.

In addition, freezing makes you sleep more easily and wake up more often. However, it’s not the case that a cold develops without prior infection and simply by sleeping with the window open. But you should avoid wet hair in combination with low bedroom temperatures.

Pollen in the bedroom

You don’t live on a busy road that makes for noise and bad air? And you don’t have a cold or freeze at night because the bedroom temperatures drop below 16 °C? Then everything should be right for you to leave your window open while you sleep, shouldn’t it? Not necessarily! Because while big cities can affect the sleep quality due to noise and exhaust fumes, there is more pollen in the air in the countryside than in more urban areas.

For many people, this is a clear disadvantage of an open window at night at certain times of the year. Especially in summer and spring, allergy sufferers then have to choose between warm bedroom temperatures and a sniffly nose triggered by their pollen allergy. Here, too, it is important to air the room during the day and vacuum it thoroughly afterwards, especially before going to bed. Washing your hair in the evening also ensures that the pollen bothers you less at night.

Increased risk of mould growth

Depending on the outside and the inside temperatures, an open window at night can also increase the risk of mould. Especially when the outside temperatures drop sharply at night and the bedroom cools down during this time, the windows should not be tilted at night and should only be opened the next morning. This is because cold air can absorb less moisture, which we release during the night through sweating and breathing.

Alternatives to sleeping with the window open

Whether you open your window at night or keep it closed is your decision. If you can’t sleep any other way, you should of course follow your needs. However, at the latest when you can no longer find restful sleep due to lack of night’s rest, pollen, and other sleep killers, there are alternatives to open windows at night.

The most important thing is regular ventilation during the day – regardless of whether you keep your window closed or open at night. You should ventilate all rooms three to five times a day for ten minutes at a time. In cold outside temperatures, five minutes are sufficient. To freshen up the room climate once more and to improve your sleep quality, airing shortly before going to bed is recommended.

In addition to regular ventilation, you can also improve air quality by turning off electrical devices, heating, and air conditioning at night. You gas and electricity bill will also benefit from this. If humidity is too high, e.g. due to heavy night sweating, you can set up dehumidifiers in the bedroom. If you have trouble sleeping because of dry air, hang some damp towels near the bed. Dry air manifests itself, for example, in a blocked nose.


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