It’s a popular hack with Nordic parents, who place their babies — yes, babies — outside to take a nap even in chilly temperatures.
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Although we’re not suggesting you take your mattress outside, sleeping with the window open in winter can give you a similar blast of fresh, cool air. But is it worth the chill?
With yet another winter storm approaching you might be feeling some trepidation about leaving your window open all night. I asked the experts the benefits and drawbacks of this Nordic sleep hack — and gave it a go myself.
The pros of sleeping with the window open in winter
“We often underestimate the importance of air quality for good sleep,” explains Dr. Jade Wu, board-certified sleep psychologist and Sleep Advisor at Mattress Firm.
“We know from research studies that both overall neighborhood air quality and indoor air quality impact sleep quality,” she explains, “so, a bedroom should be well ventilated.”
“Ventilation will help clear out the stale indoor air and excessive CO2 buildup from the previous night, resulting in less grogginess in the mornings,” agrees Dr. Jordan Burns D.C., Sleep Expert for Amerisleep.
Research indicates high levels of CO2 in the bedroom can worsen sleep quality, while lower levels support deep sleep and fresh mornings.
Dr. Burns adds that ventilation also ensures a constant supply of cooler air. “This supports the body’s normal decrease in temperature as we sleep,” he explains, “providing an important signal for the body to enter deep, more restorative sleep.”
With an open window you might better maintain the optimal bedroom temperature of 65 to 70°F (so hands off the thermostat.)
“Many people report that their sleep onset time has decreased and they feel clearer-headed in the mornings due to the perceived cleanliness of their bedroom and improved airflow,” says Dr. Burns.
The cons of sleeping with the window open in winter
“There is a point at which the bedroom temperature becomes so cold that the body can go into a state of ‘survival’ rather than ‘recovery’,” warns Dr. Burns.
As Dr. Wu points out; “temperature control is important.” You might lose that “control” aspect when you bring the outside elements into play.
And if you’re so cold you can’t relax, you’ll struggle to drift into deep, restorative sleep.
Dr. Burns also notes that those with back or joint pain might find cold weather exacerbates “morning stiffness.”
Plus, when you open up the window, it’s not just fresh air you’re letting in.
“Outdoor noise, pollen, or poor outdoor air quality could negate the positive effects of ventilation,” says Dr. Burns.
What happened when I tried it
While I love sleeping with the window open during summer, it had never occurred to me to carry on the habit during winter, in the same way I stop wearing shorts after September.
I’ll admit, I’ve been meaning to try this hack for a while but between the cold and the wet, I always had some reason to not open the window.
Eventually I ran out of excuses, bit the bullet and let the outside in.
The biggest benefit was the ventilation. It helped banish the ‘stuffy’ feeling that can plague my bedroom in winter, so I feel asleep and woke up taking deep breaths of fresh air.
And it wasn’t as cold as I was expecting, particularly during the night. The slight bite to the air was combatted by my layers of bedding.
My big challenge came in the morning, when I had to convince myself to leave my cocoon and step into a bedroom that was decidedly chilled.
Gritting my teeth and getting on with it (plus a handily placed robe) was the only solution. But I’m not sure I need another excuse to stay tucked up on a dark winter’s morning.
How to nail the Nordic sleep hack
“While sleeping with a window cracked open can be beneficial for sleep, even in colder temperatures, it requires some thought and planning,” says Dr. Burns.
Here are our expert suggestions:
1. Only open the window slightly
“I suggest opening the window slightly to ventilate the bedroom while maintaining the warmth of the bedding, to establish an environment for the body to relax and recover fully throughout the night,” advises Dr. Burns.
You’ll still get the benefits of improved airflow without risking an uncomfortable influx of icy air.
(And if you’re frequently waking up the wrong temperature, you might want to invest in a new mattress — we test every bed in our best mattress guide for temperature regulation.)
2. Use a hot water bottle
The German ‘lüften’ trend also encourages you to throw the windows open as part of your nighttime routine.
However, it comes with a tiny twist: you use a hot water bottle to warm your bed as you do so.
While your room cools your bed heats, hopefully creating the perfect conditions to drift off.
3. ‘Burp’ your bedroom
‘House burping’ is the latest TikTok sleep trend to go viral and despite the off-putting name, there are benefits to this hack.
‘Burping’ your house involves opening the windows and doors for a brief period of time to increase ventilation without allowing the heat to escape.
A quick ‘burp’ helps clear CO2 and other lingering nasties in the air, for better air quality as you get into bed.
“I wouldn’t necessarily leave the window open all night, especially in cold weather,” agrees Dr. Wu.
“Personally, I leave the window open during the summer,” she says. “In cold months, I leave my bedroom door open.”
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