It’s night, you’re hot, and you need airflow in the sleeping area. That’s completely understandable.
Numerous studies have highlighted the sweet spot for sleep, and it’s 60 to about 72 degrees Fahrenheit for most people.
I’ve slept with screened windows open in spring and summer myself. Like me, you’ve probably wondered what are the good things and are there any drawbacks to keeping your windows open to sleep.
Are there viable alternatives to sleeping with your or your child’s window open? Can leaving windows open cause sickness (the quick answer: sickness, no; humidity & mold, yes)? This is a fascinating and multi-faceted topic, so let’s dig in.
Sleeping with your window open can improve the air quality in your bedroom (e.g., reduce Carbon Dioxide, Radon, and diffuse smoke-filled air), improve heat and humidity regulation, thereby reduce energy bills, and provide you with the soothing sounds of nature. All of which has been proven to increase your sleep quality and quantity!
Let’s explore some risks, several benefits, and some alternatives to keeping bedroom windows open at night, such as whether headache or sickness go hand-in-hand with open windows.
Benefits of Sleeping with an Open Window
Carbon Dioxide (CO2) Reduction
Given that we are estimated to spend nearly a third of our lives in the bedroom environment, it’s no surprise that airflow and ventilation affect both our sleep quality and our waking life.
During sleep, we are basically immobilized in one area for six to 11 hours (for children) and we’re generating a lot of carbon dioxide when we exhale.
The same goes for our pets! If all our doors and windows are closed, that’s not a good thing.
High indoor carbon dioxide levels inside a home can contribute to building-related illness (BRI) or SBS, “sick building syndrome.”
BRI is a stronger indicator in that “symptoms of diagnosable illness are identified and can be attributed directly to airborne building contaminants” (Environmental Protection Agency).
Both BRI and SBS are associated with acute or immediate health problems according to the EPA. SBS indicators include headache; eye, nose, or throat irritation; dry cough; and nausea that usually resolve soon upon vacating a building, whereas BRI symptoms are fever, coughing, and muscle aches and may take longer to recover from after leaving.
And so, some researchers think not nearly enough attention has been paid to indoor air quality with respect to sleep.
To that end, Dr. Asit Mishra of Eindhoven University of Technology and co-authors have published the results of a sleep study of a small population of healthy college students.
“Bedroom CO2 level, temperature, and relative humidity were measured over 5 days, for two cases: open window or door (internal, bedroom door), and closed window and door” in 17 healthy volunteers (Source).
Mishra and colleagues obtained self-reported subjective measurements and objective actigraphic measurements (sensors tucked under pillows, detecting sleep shifts and movement patterns, and armbands).
In this study, the CO2 levels during open-window or open-door periods were markedly lower (717 ppm when open versus 1,150 parts per million when closed).
Although the closed environments in this study tended to have less or quieter background noise, humidity levels were similar in closed and open settings (Source).
In these young, healthy volunteers, both bed and skin temperatures were higher in the closed group. Also, “The number of awakenings and sleep efficiency improved as carbon dioxide levels decreased” (Reuters).
Another study, also of a small population of college students, assessed bedroom air quality and “next-day performance” in these students. Its findings? “Objectively measured sleep quality and the perceived freshness of bedroom air improved significantly when the CO2 level was lower, as did next-day reported sleepiness and ability to concentrate and the subjects’ performance of a test of logical thinking” (Source).
It’s important to remember that “Sleep quality is affected by many factors, such as health and emotional states, bedding conditions and different environmental conditions, including noise levels and temperature,” said Dr. Nuno Canha of the University of Lisbon in Portugal (Reuters).
Dr. Canha also elaborated: “The exposure [to CO2, particulate matter, and volatile organic compounds, as through smoke, air pollution, or building materials, cleaners, and furniture] we are under while asleep is continuous . . . and we should play it safe in order to breathe better air during sleep.”
To that end, before opening a window you might like to consider Air Quality Index (AQI) tools to evaluate your area’s air quality, such as the apps AirVisual or Plume Air Report for Android or Air for macOS (Source).
You can also browse your local air quality for free at Breezometer (Source).
Opening Windows Decreases Radon
Radon is an toxic gas that emanates from uranium decay in the soil, so it is most prominent in basements and ground floors.
After smoking, radon is the next most common cause of lung cancer in the U.S.
Opening basement or ground-floor windows, including at night, can help reduce radon, but will not solve the issue of it entering through foundation cracks (Source).
Opening a window or the door to the bedroom can improve airflow and ventilation.
It is a well-documented fact that optimal sleep temperatures tend to fall between 60 and 72 degrees Fahrenheit. Whereas some can sleep as low as 60, others prefer a little warmer.
A drop in body temperature precedes and induces sleep. As H. Craig Heller, PhD, Stanford professor of biology and textbook medical author, puts it: “When you go to sleep, your set point for body temperature—the temperature your brain is trying to achieve—goes down” (Source).
The brain stem is highly involved in sleep regulation.
You might have to experiment with your thermostat, light-blocking masks or curtains, and ventilation, including personal fans (Source), to find your exact “sweet spot” of temperature and light/darkness for ideal sleep.
I’ll let you in on one of my light-hating husband’s sleep tools: Nicetown’s thermal insulated curtains.
We found that the cappuccino color blocks light well for our single ground-floor master bedroom window, paired with blinds.
Other Amazon customers seem to agree, and they even report good sound-blocking properties as well!
Somewhat related to coolness is the humidity (or moisture content) of air. The general rule of thumb for comfort is that if it’s more humid inside than out, opening windows could very well help.
How do you know what the moisture content of air is? Why, through a hygrometer of course! They are made for indoors and outdoors.
One workhorse indoor hygrometer and temperature gauge I’m eager to try is the affordable and very highly rated digital ThermoPro T50.
- 【Air Comfort Indicator】Humidity meter with humidity level icon indicates air condition -- DRY/COMFORT/WET, allowing this humidity sensor to ensure you’re always aware of changes to your...
If you live in a humid state or region, there’s not much you can do about outdoor climate. However, if your home is routinely too humid inside, you’ll want to address your ventilation, windows and doors, and heating and air-conditioning systems (an HVAC specialist can certainly help!).
Alternatively, dehumidifiers can help you “demoisturize” your home. Here is a highly rated inexpensive dehumidifier from Amazon:
- High-Efficiency Dehumify：ALROCKET portable dehumidifier with 35oz(1000ml) capacity tank extracts up to 16oz(450ml) of water daily in a humid environment of 86°F and 80% RH. ALROCKET dehumidifier...
Diffuse Smoky Air
Opening the window to sleep in an adult’s bedroom can help disperse tobacco smoke and other pollutants.
If you are a smoker or live with one, opening a bedroom window nightly in a quiet, nonpolluted area is an excellent idea.
Numerous studies have shown the health risks of second- or even third-hand exposure to tobacco smoke, including this small sleep study comparing indoor air quality in smokers’ and nonsmokers’ bedrooms (Source).
As one study sums it: “Environmental tobacco smoke is one of the most important risks for respiratory symptoms and diseases worldwide” (Source).
Reducing or stopping indoor air pollutant sources, such as volatile organic compounds from paints, cigarette smoke, and the like, is key to helping mitigate conditions such as asthma, allergies, chronic bronchitis, and COPD.
A second step, however, is choosing good air filters.
Consumer Reports has evaluated air filters and rated both the Aprilaire Healthy Home 213 MERV 13 (first, less expensive) and the Aprilaire Allergy & Asthma 216 (second) highly in removing dust, pollen, and smoke in a forced-air heating/cooling system (Source).
- BUY WITH CONFIDENCE This genuine Aprilaire 213 replacement air filter was designed and manufactured in the U.S.A. by Aprilaire – the leader in indoor air quality solutions to optimize the...
Reduce Energy Bills
According to the U.S. Department of Energy, energy-efficient windows reduce electrical/gas bills and, therefore, fossil-fuel consumption.
They say window heat gain and loss drives 25% to 30% of residential energy use (Source).
But what if you’re in a condo or apartment, cooler climate, or can’t afford new windows?
One frugal way to disperse heat build-up from springtime or summer sun is to open your windows at night—with the caveat that humidity will still creep in through windows (and can damage books, furniture, flooring, electronics, and textiles and has negative health implications).
A rule of thumb? “If you live in an area with cooler summer temperatures, opening the windows and keeping the AC turned off as much as possible will save energy costs in the long run,” according to heating and AC/home improvement professional Luke Caldwell (Source).
Another thrifty tip from Caldwell: “Try opening windows and turning off your air conditioner at night to let in cooler air. Then shut the windows and shades in the morning to trap the cool air in your house.”
Night noise is white noise to some people. As I explored in a previous post, music, white noise, or the sounds of nature can have a lullaby effect on some people (Source).
Do you live on a quiet suburban street or in a rural location? Are you far removed from highways and streets, train tracks, airports, factories, loud outdoor dogs, roosters, or rude neighbors?
If you can answer yes to those—allergies, safety, security, and adverse weather notwithstanding—I personally say why not give open windows a try?
Risks of Opening Windows at Night
Risks exist along a spectrum, both of how likely they are to happen and their severity.
Personal values also figure into it. So, for example, my personal ranking of “child or pet falling/escaping out a window” would rise far higher than, say, the drawback of rain coming in the open window and damaging a curtain, carpet, or casement.
That said, here are the most probable and notable risks from sleeping with windows open, which can modulate based on your use of a screen or other protective devices; location and building; neighborhood security; your personal risk aversion; presence of allergies or health conditions; and the time of year (just to name a few).
Every year in the United States, approximately 5,000 injuries are caused by window falls in children 10 years and younger (Source). Worse still, an average of 12 children under age 10 die because of window falls (with under-5s the highest affected).
Leaving bedroom windows open in a young child’s room to sleep at night presents too many risks of falling, injury, or security, such that I do not recommend it for children 10 and younger.
Pet Escape Risk
Pets such as cats and birds are most likely to escape through windows, and in the case of cats, they can be injured after falling from a window.
The old old adage that a cat lands on their feet is true, but it doesn’t mean they don’t get hurt, sadly.
In fact, veterinarians coined a phrase because cats fall from windows so often: High-rise syndrome. And, ironically, “Cats that fall from heights of between 2–7 stories typically sustain more, and worse, injuries than those that fall from greater heights” (Source).
In a landmark study published in the Journal of the American Veterinary Medical Association, a remarkable 90% of cats who fell from windows sustained thoracic (chest) trauma.
With cats, the extent of injuries may not show up until 48-72 hours after the fall.
Also, domesticated cats or birds who escape windows face many other dangers than falling: They may starve, be hit by cars, get poisoned, be infested by parasites, or end up as homeless strays in a shelter.
If you have cats, don’t count on a screen alone to keep them inside.
According to Safe Streets, a home burglary occurs about every 13 seconds in the U.S., and criminals spend only about 8 to 12 minutes in the home (Source).
A first-floor window is the second most common point of entry for burglars after the front door, at 23%.
Use your local crime statistics to weigh your risk of opening windows at night.
Finally, if crime is a problem in your area, consider a security system if you are at home and want to occasionally open your windows at night.
Drones and mobile phones are nearly ubiquitous in our society, and their sophistication improves exponentially.
My Drone Lab (MDL) says that, although entry-level drones are unlikely to record you in your home and evade detection, “the truth is, there are drones that make use of technology that can see what is inside your house” (Source).
MDL also notes that generally, a private citizen is not going to have as agile and undetectable a drone as the military or law enforcement already does.
That said, only you can assess your surveillance risk and take steps to block neighbors or strangers from recording you in your home without your knowledge or consent.
If windows are wide open at night, with no curtains, in a populous area, you may well be, at a minimum, heard or seen by neighbors, like in the Hitchcock movie about voyeurism, “Rear Window.”
Humidity or Adverse Weather
It’s a Goldilocks situation: Both your home and your health can suffer from too little (dryness, aridity) and too much moisture (humidity).
Opening windows (if it is more humid outside than inside) can bring in air filled with moisture or actual rain during storms. Moisture relates to humidity, and too much humidity can be detrimental as follows:
- Humidity can foster mildew and mold growth
- Humidity can damage everything from toys and books to paintwork, wallpaper, furniture, floors, walls, and brickwork (Source).
Outdoor Noise Affecting Sleep
Windows let in more outside noise, in general, than walls. If noise levels outside your home or dwelling regularly exceed those indoors, then it’s likely not a good idea to leave your windows open at night or while sleeping.
I know I don’t like to be woken by sirens, my neighbor’s muffler-less car, or even gentler noises of early birds calling to each other!
Ensuring that you have really good windows and insulation can reduce noise; acoustic storm windows fit the bill but can be pricey according to Pennsylvania State University (Source).
Pollen or Other Allergens
Before deciding to sleep with windows open, simply put, know your or your family’s allergy triggers, if any.
Insect or Unwanted Animal Intrusion
Fortunately, it is possibly to somewhat bug-proof your windows through caulk, foam, and weatherstripping, plus mending any screen holes.
I’m especially concerned for those of you in scorpion country, where these critters can wiggle in through cracks in window frames or panes (Source).
So, you will have to think twice about opening your windows at night and creating a more welcoming environment for insects or potentially other wild critters.
Oxygen Fuels Fires
If you have good smoke detectors (check those batteries at least twice yearly!) in appropriate numbers for your dwelling’s square footage, bravo!
But be aware that keeping windows open at night can help create an environment favorable to fire, which needs oxygen to survive.
So, please also be sure to keep home fire extinguishers in areas like the kitchen, garage, and workshop and be vigilant about maintaining your fireplaces, wood stoves, and ovens.
Alternatives to Opening Windows at Night
The best alternative depends on why you are opening windows in the first place: coolness, humidity help, white/natural noise, dispersing CO2, improving airflow?
“Opening an internal door can be a reasonably good alternative [for circulating air, boosting indoor air quality, and lowering CO2] if you don’t want to open windows, either for noise concerns or security concerns,” Dr. Mishra said (Reuters).
You might explore different air conditioning systems or air filters, personal fans or dehumidifiers (as aforementioned), or other sleep techniques or products that relate to your difficulty—cooling mattresses for hot sleep, white noise makers, or even music/meditation before bed or sleep headphones during.
If you have a stuffy nose and/or sneezing and itching and have tried conventional over-the-counter allergy treatments and what clinicians like to call “tincture of time” (i.e., your condition doesn’t resolve itself with time), please consult a medical professional before you decide to keep your window open every night.
It could be that seasonal (outdoor) allergens are keeping you up at night. As a fellow allergy sufferer, I send you my best wishes!
Does Opening Windows at Night Cause Colds, Flu, or Pneumonia?
Keeping the windows open does not directly cause illness, such as colds, flu, or pneumonia.
Colds and flu are viruses spread mainly by the airborne route; broadly speaking, they are contracted by exposure to droplets expelled by sick people into the air via sneezing or coughing (Source).
Pneumonia results from bacteria, viruses, or fungi; viral pneumonia typically stems from influenza (Source).
Bacterial pneumonia is the most common type.
Fungal pneumonia exacts the heaviest toll in immune-compromised people (e.g., those undergoing chemotherapy for cancer treatment or people with HIV or AIDS; Source).
Does Opening Windows at Night Affect Allergies? Can it Cause Headaches?
Headaches can be loosely connected to windows if, for example, you are exposed to smoke, mold, tree, or plant allergens when said windows are open.
But allergies are a complex immune overresponse to allergens that triggers an immunoglobulin E (IgE) overload, not because of windows being open (Source).
If you have chronic headaches of idiopathic (unknown) origin, your medical provider should be able to work with you to pinpoint a cause or diagnosis, whether it be migraines, allergies, or possibly related to mold exposure in humid conditions (Source), or SBS (sick building syndrome), as discussed earlier.
Can I Leave the Window Open While Raining?
You can leave the window open while raining, but should you?
Rain of course means humidity. Humidity can damage household electronics, books, textiles, furniture, walls and flooring, and even the casements.
Humidity also creates a favorable environment for mold growth and can attract pest insects such as mosquitoes, bedbugs, and silverfish (risks I wrote about here).
As I write this article, I am listening to a YouTube rainstorm (specifically, this one), so I empathize with your desire to listen to nature sounds for relaxation or meditation, sleep, or concentration.
But unless you’ve got really good dehumidifiers, no allergies, and nothing rain could damage, I’d probably recommend keeping the windows only cracked open (or shut) during rain.
Can I Leave a Window Open At Night with a Baby?
If I were your pediatrician, I’d say this is a hard pass unless maybe perhaps perchance you sleep in the room with the baby or toddler and can monitor them all night (or day) long.
Did you see those earlier data about children falling from windows? As a parent myself, I shudder to have that happen to you or your little one.
Besides falling (because a child of a certain age and size is capable of climbing and pushing out a flimsy screen), if windows don’t have stops or locks on them, there is the potential for a security risk, for adverse weather, and for unwanted critters if the screen is inadequate.
That said, if you’re supervising closely and want to crack a secure ground-floor window open every now and again for a couple hours in baby’s room and she doesn’t have allergies or asthma (and there’s no outdoor air pollution), there’s little risk that I can see.
Even as a risk-averse person, I can see the conditional merits of opening your windows from time to time to cool your bedroom and improve airflow.
As a review, opening windows at night can do the following good things for you:
- Cool and/or dehumidify the bedroom.
- Reduce CO2 levels, radon gas, and other indoor air pollutants (although there are other good ways to do this, like keeping heating and cooling systems and ventilation up-to-date, air filters, using fans strategically in rooms, and opening interior doors).
- Provide natural sounds to help sleep.
- Curb energy bills.
So long as you, as a healthy adult, are mindful of the risks of opened windows and act to mitigate or reduce any that you can, the chances are good that you can sleep with open windows from time to time when the conditions are right.
In the meantime, I hope you find a sleep solution that works well for you.