Should You Open Your Bedroom Window in Winter for Better Sleep?

On a winter night, opening a window in your bedroom can be a hotly contested topic. Some folks love the cold air and swear it helps them fall asleep faster and wake up feeling more rested. Others worry it drags in unwanted dry air and outdoor allergens. So, who's correct?

To find an answer to this age-old question, we asked two medical experts who broke down how temperature, ventilation, and air quality affect your body overnight, as well as who should (and shouldn't) consider cracking a window before bed.

Can Opening a Window Improve Sleep?

In some instances, having a window open can improve your sleep—but not in every case. Dr. James J. Chao, co-founder and chief medical officer of VedaNu Wellness, says the benefits (or lack thereof) are directly linked to what’s coming through your home’s window. 

"Lowering your core body temperature by using cooler air will help you fall asleep faster," says Dr. Chao. "However, using unfiltered cool air will introduce pollutants (i.e. allergens) that can cause inflammation in your nose, sinuses, and upper airways."

Dr. Mia Kazanjian, a board-certified radiologist, points to a 2022 study that found sleep quality and duration improve with an open window when the air outside is cleaner than the air inside. But if the air quality outside is poor, opening a window can worsen health condition and sleep quality rather than improve them. 

How Cold Air, Ventilation, and Humidity Affect Your Body Overnight

From how quickly you fall asleep to how deeply you rest, overnight comfort is shaped by the relationship between temperature, airflow, and moisture in the air.

Cold Air

A hot, stuffy bedroom isn't ideal for sleep. Dr. Kazanjian explains that for most, rooms in the low to mid-60s (degrees Fahrenheit) generally provide ideal sleeping conditions. However, Dr. Chao says that there isn’t a specific "magic number" to adhere to since sleep quality is affected by more than just room temperature. 

Dr. Chao adds that while lower temperatures may initially support thermal regulation, the body has a threshold. “Depending on whether or not you are acclimated to the temperature, your body will begin to initiate heat-conservation mechanisms such as vasoconstriction,” he says. “Vasoconstriction may disrupt the deeper stages of sleep, especially in people who do not have enough body fat or those who suffer from hypothyroidism.” 

Ventilation and Humidity

Fresh airflow can make a bedroom feel more comfortable, but it can also affect humidity—especially in winter. Cold outdoor air also tends to be very dry, so opening a window may lower indoor humidity levels even more. 

“Dry air dries nasal passages and skin, which I frequently observe to worsen snoring, morning throat irritation, and eczema flares,” Dr. Chao says. “The skin also loses moisture overnight, and dry air exacerbates this process. Therefore, while airflow is important for comfort, so too is the hydration of the air.” 

While ventilation matters, so does the level of moisture in the air. For peak sleep comfort, your airflow should be balanced with adequate humidity.

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When Cracking a Window Helps

In certain conditions and for the right sleeper, cracking a window can be beneficial.

• You’re looking to remove stuffiness from your bedroom: Dr. Chao says opening a window won’t generally increase your oxygen levels, but it can make the room less stuffy by bettering ventilation.
• Your outdoor air quality is good: “Making sure the outside temperature, air quality index, noise, and humidity levels are appropriate is important,” Dr. Chao says.
• Your window is on an upper floor: Unless your lower-floor windows have safety mechanisms (or are able to open just a crack), Dr. Kazanjian recommends only opening upper-floor windows for safety.
• You have an indoor air purifier: If you want to have your window open pre-slumber, Dr. Kazanjian notes that setting up an air purifier in your bedroom is a solid play. “They’re helpful to filter out any pollutants from outside,” Dr. Kazanjian says. 

When to Keep the Window Closed

Here's when it's probably best to keep your windows closed on winter nights.

• You live in an urban area: “In most urban areas during the winter months, the primary sources of heating are dry, commercial heaters, wood-burning stoves, and heavy industrial pollution,” Dr. Chao explains. “Add in high winds and changing atmospheric pressures, and you may be drawing in particulate matter at concentrations greater than you are blowing out.”
• You have bad allergies: Unfiltered outdoor air can introduce pollen, mold spores, or particulate matter that may irritate your nose and airways. This inflammation can disrupt breathing and sleep (even if the room feels cooler/ fresher), Dr. Chao says.
• Your air quality index is bad: Keep your window shut if you have pollutants in the air , like from heavy vehicle traffic, wood burning or smoke, and other carcinogens, Dr. Kazanjian says.
• You’re sensitive to cold: Too much cold air can cause muscle stiffness and poor sleep. So if you’re prone to chilliness—and the air outside is frightful—keep the window shut.