Why You Should Be Opening Your Windows in the Dead of Winter
When temperatures plummet, the last thing most people think about is throwing open their windows. In places like Canada, where winter means freezing air and high heating bills, it seems counterintuitive — why waste precious warmth? But in Germany, not only is winter ventilation a well-established practice, but in some cases, it’s even written into rental contracts.
The reason? Indoor air quality.
The Science Behind Lüften
The German practice of lüften — which translates to “ventilating” — involves fully opening windows for a short period to flush out stale air and bring in fresh outdoor air. This isn't just a quirky tradition; it’s a science-backed way to maintain a healthier and fresher indoor environment.
Many German landlords require tenants to ventilate their homes regularly to prevent mould growth, a common problem in well-insulated spaces where humidity builds up. It’s not unusual to find rental agreements that specify opening windows at least three times a day usually in the morning, midday, and evening.
Why It Matters, Even in Freezing Temperatures
Modern homes are built to be energy-efficient, meaning they’re also airtight. While this is great for keeping heat inside, it also means that pollutants — like carbon dioxide, volatile organic compounds (VOCs) from furniture and cleaning products, and airborne allergens — get trapped.
The result? Indoor air can be multiple times more polluted than outdoor air.
Lüften helps by:
- Flushing out indoor pollutants that accumulate from cooking, heating, and off-gassing furniture.
- Reducing excess humidity, which prevents mould and bacteria from thriving.
- Boosting oxygen levels, improving focus, sleep, and overall well-being.
How to Lüften Properly
There are two key ways to ventilate effectively:
- Shock Ventilation – Open a few windows wide for about 10–15 minutes to rapidly exchange air.
- Cross Ventilation – Open opposite windows and doors to create a cross-breeze for maximum efficiency.
The best part? You don’t lose as much heat as you think. Warm air naturally rises, and with a short, intense exchange, your furniture and walls retain heat, allowing your space to warm back up quickly.
A Simple Habit with Big Benefits
If you're skeptical about adopting lüften, try it for a week. You might notice:
- Fewer headaches and less stuffiness
- Improved concentration and sleep
- Less condensation on windows (a sign of trapped humidity)
Fresh air isn’t just about comfort, it’s about health and longevity. During the pandemic, studies found that opening windows reduced SARS-CoV-2 transmission risk by over 70% in residential and healthcare settings by diluting viral particles in enclosed spaces.12 So, the next time you’re bracing for winter flu season, take a page from Germany’s book: crack those windows open, even for a few minutes.
ERTH360 Air: Elevating Indoor Air Quality
Lüften is just one part of the bigger picture when it comes to healthy homes. ERTH360 Air is our whole-home clean air solution that seamlessly integrates ventilation, air purification, and advanced filtration — because fresh air shouldn’t be a luxury, but a standard.
Visit our solution page to learn more.
1 https://pmc.ncbi.nlm.nih.gov/articles/PMC7115766/
2 https://www.rehva.eu/rehva-journal/chapter/implications-of-covid-19-pandemic-for-application-of-natural-ventilation
