Opening windows during the coldest part of winter may appear counterintuitive for wellness. Yet in Germany, it’s a customary routine known as lüften: ventilating one’s residence daily, even amid freezing temperatures.

The term lüften, meaning “airing out” in German, is widely practiced because German residences are highly insulated, and window ventilation is believed to decrease mold, moisture, airborne contaminants, and smells. During winter, some Germans also perform stoss lüften, or “shock ventilation,” by fully opening every window for five to ten minutes. This German custom is gaining popularity in America—particularly on social media—where practitioners call it “burping” their house.

Yet does lüften truly improve your health? Specialists overwhelmingly affirm that it does.

Individuals frequently worry more about exterior air purity than interior conditions, notes Ian Cull, founder and chief science officer at an indoor air quality consulting and training firm. However, he states that “generally, indoor air quality is poorer than outdoor air.” Various sources—from candles and cooking to dust, new furnishings, and household cleaners—can pollute indoor environments.

Occasionally, humans themselves create contamination. When indoors, people constantly release microscopic particles, explains Mark Hernandez, a biomedical engineering professor and director of the aerobiology and disinfection laboratory at the University of Colorado Boulder. “Each of us carries our own microbiome,” he remarks. “We continuously shed skin cells and hair. This rarely troubles most individuals, except for those with asthma or serious allergies. Opening windows essentially dilutes and eliminates what we’ve shed.”

Certain individuals are more reactive to airborne chemicals and allergens than others. “The effects of indoor air quality can be difficult to comprehend because experiences vary so widely between people,” he observes. Nevertheless, the COVID-19 pandemic underscored the significance of indoor air purity. “Air quality represents a crucial component of healthy living,” Cull emphasizes. “It’s no longer solely about physical activity, nutrition, and rest. Today, indoor air quality has become an essential part of that discussion.”

Below are several advantages of ventilating your residence.

Enhanced sleep quality

Research indicates that sleeping with windows open enables individuals to drift off faster and rest more deeply, according to Cull. “Keeping windows open during sleep has demonstrated positive effects.”

However, this practice only proves valuable in relatively quiet locations. A study featured in Science and Technology for the Built Environment revealed that participants snored less and experienced fewer awakenings when sleeping with open windows. Conversely, some individuals reported poorer sleep due to being disturbed by external sounds.

Lynelle Schneeberg, a sleep psychologist at Yale University, suggests that performing lüften immediately before bedtime may promote more restorative nighttime rest. “Recall that sensation of climbing into freshly laundered sheets?” she asks. Through lüften, “you essentially recreate that experience daily. I believe it’s truly an excellent practice.”

Enhanced psychological wellbeing

Currently, extensive research is underway examining indoor air quality within learning environments, Hernandez notes. One particular study discovered that classrooms exhibiting elevated carbon dioxide levels—resulting from overcrowding and inadequate ventilation—correlated with reduced performance on cognitive assessments.

“Regarding overall wellness, mental acuity, and occupational productivity, a growing body of research confirms that fresh air is essential for optimal functioning in indoor spaces,” Hernandez explains. Lüften may also offer emotional advantages. A study in BMC Geriatrics determined that elderly individuals residing in well-ventilated dwellings exhibited lower rates of depression than those in poorly ventilated homes.

Laurence Chan, an assistant professor of medical psychology in Columbia University Irving Medical Center’s psychiatry department, views lüften as providing a distinctive chance for mindful awareness, particularly for sedentary individuals, those confined indoors frequently, or people vulnerable to mood disturbances and anxiety.

“This practice allows us to pause from concentrated activities and redirect our focus,” he observes. “When we experience that gust of fresh air—perhaps a brisk chill—we heighten awareness of our senses. What are we experiencing? What occupies our thoughts? Fresh air provides an opportunity to exist in the moment and enjoy a restorative pause.”

Several important exceptions

“Home ventilation is generally beneficial,” Cull acknowledges, “though certain circumstances warrant caution.” For instance, when exterior air quality deteriorates below interior levels, “open windows may prove harmful.” Such scenarios include wildfires, dust storms, peak pollen periods, high mold spore counts, regions with industrial emissions, or city centers during commute times. “One must carefully consider timing and conditions before opening windows,” he advises.

Hernandez reports keeping his windows open whenever weather allows. Even in cold conditions, his household opens them upon waking, after returning from work, and prior to sleep. Their motivation stems not only from his aerobiology research but also from his wife’s upbringing with a Romanian saying that echoes lüften principles: “Should you neglect to open windows, the physician will enter through your door.”