Do you leave a window open in the winter? It can be a polarizing topic. Many of us like a bit of fresh air during the cold season, but if you’re in charge of paying the utility bills, you might have a different opinion. I once lived in an apartment where the radiators got cranked up to “inferno” every November, and you better believe I opened the window. (Sorry, landlord, wherever you are.)

Of course, the electrician in me now understands, and cares, about energy usage and the effects of humidity on building materials. But does that mean I can’t leave a window open in winter on occasion? Can it ever be a good idea? And does the weather play a role? Ahead, I talked to experts in indoor air quality and heating, ventilation and air conditioning (HVAC), as well as a scientist from the National Weather Service, to find out.

Benefits of Leaving a Window Open in the Winter

Let’s start with the pros. If you’re a little claustrophobic like me, you’ll like this section.

According to Allen Rathey, director of the Indoor Health Council, today’s houses are much more airtight due to higher energy efficiency standards than they were in past decades. That means less air exchange between inside and outside, so opening a window in the winter can offer several benefits.

  • Improved air quality: Opening a window can reduce stale air, plus indoor air pollutants like carbon dioxide, vapors from cleaning products and cooking fuel byproducts.
  • Humidity control: Dry winter air can do a number on your skin and lungs. “Fresh air can help regulate indoor humidity levels, preventing excessive dryness,” says Brad Roberson, president of Aire Serv heating and air conditioning.
  • Odor removal: Even with a range hood or exhaust fan, cooking smells permeate every nook and cranny of your home. If you’ve ever lived over a restaurant, you know what I’m talking about.
  • Mental well-being: Darkness at 5 p.m. can be a downer, but opening a window may help. “Some people find fresh air invigorating,” Roberson says, “and it can help improve your mood and overall sense of well-being.”

Cons of Leaving a Window Open in the Winter

The biggest con of leaving a window open in the winter is the loss of heat. When you open a window, your HVAC unit eventually kicks on to replace the conditioned air that escapes. That could reduce the energy efficiency of your unit and raise your energy bill, Roberson says, especially if you leave a window open near the thermostat.

Leaving a window open during the winter also wastes energy, even if you’re not so concerned with your utility bills. Unless your home is completely powered by solar and wind, your HVAC is consuming a dwindling supply of fossil fuels.

Should You Leave a Window Open Year-Round?

“Leaving a window open year-round is generally not advisable,” Roberson says. “In the winter, it’s usually more energy-efficient to keep windows closed to conserve heat, while in the summer, you might want to open windows to ventilate your home.”

But, “if you’re trying to improve indoor air quality, control humidity, or simply enjoy the benefits of fresh air, opening a window occasionally may be helpful,” Roberson says. “The key is to strike a balance, ensuring that it doesn’t lead to excessive heat loss or discomfort. Using a window briefly during milder winter days can help achieve the benefits without causing your HVAC system to work excessively hard.”

Should I Leave My Window Open in the Winter?

It’s up to you, though experts generally advise being judicious. “There is no ‘one-size fits all’ when it comes to our indoor spaces,” Rathey says. Roberson adds: “You can leave a window open in the winter, but it’s important to be selective about when and where.”

Here are some situations that might warrant cracking a window:

  • In stuffy or humid rooms: It’s best to keep indoor relative humidity between 30% and 50% to keep mold at bay. “An inexpensive temperature and relative humidity meter can help show impacts from a slightly opened window, and flag you to close it when too much damp/cold air enters,” Rathey says.
  • When outdoor air quality is good: Air pollution contains harmful volatile organic compounds (VOCs), dilution of which “may reduce impacts to those with chemical sensitivities, unless the outdoor air is more polluted than inside,” Rathey says. Check your local air quality index at AirNow.gov to make sure.
  • On sunny and warm(er) days: Give your HVAC a break by taking advantage of good weather and natural heat from the sun. If you’re sensitive to airborne allergens and dust, ventilating may reduce these contaminants, Rathey says.
  • If your windows have locks: “An open window can be an entry point for intruders,” Roberson says, “especially when you’re asleep or not at home.” Rathey says putting sash locks on your windows, allowing them to open just a few inches, can mitigate security concerns.

FAQ

Should you leave windows open during extreme weather?

No. It’s a myth that you should open windows during tornadoes, and Kate Abshire with the National Weather Service (NWS) says that wind and hail from thunderstorms can cause glass to shatter, so it’s best to stay away from windows entirely instead of wasting time trying to open them. In rare cases, lightning can enter older homes through cracks around windows.

Can you leave the window open with a dehumidifier?

It’s not a good idea. Dehumidifiers are intended to remove moisture from confined spaces. Bringing in a continuous supply of fresh air from outside, especially if you live in a humid climate, will cause the dehumidifier to constantly run.

How much does it cost to leave a window open?

It depends on your climate, the size of your home, and the type, size and efficiency of your HVAC system. But, the cost can be significant. As a rough example, let’s say you have a 3-ton unit that uses 3,000 watts (3 kilowatts) per hour. Using the October 2024 national average cost for electricity ($0.177 per kilowatt-hour), if your HVAC kicked on just one extra hour a day, your electricity bill would rise approximately $200 per year.

About the Experts

  • Kate Abshire is the acting NWS Severe Weather Program Manager in the Severe, Fire, Public, and Winter Weather Services Branch of the National Oceanographic and Atmospheric (NOAA)/National Weather Service.
  • Allen Rathey is the director of the Indoor Health Council, a consortium of cleaning professionals and health experts dedicated to healthy indoor spaces. Rathey was previously the president of the Housekeeping Channel, The Healthy House Institute and the Healthy Facilities Institute.
  • Brad Roberson is a heating, ventilation and air conditioning expert and the president of Aire Serv, a trusted name in the field of heating and air conditioning installation, maintenance, and repair with more than 200 locations across the United States and Canada.

Sources

Author
Ally Childress
Ally Childress writes practical, informed stories and how-to guides for Family Handyman and Reader’s Digest. An experienced electrician, Ally's beat naturally includes electrical and construction topics. She also tackles cleaning, gardening, technology, bugs and anything else you can throw at her. She has a knack for finding just the right subjec...
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Ally Childress