Windows wide open, five minutes: heating and airing the German way (Stoßlüften)

Heating season has begun

Once the clocks go back this weekend, it will be getting dark by five. In German homes the months from October to April are usually called the heating season (Heizperiode). Instead of underfloor heating or air conditioning units, most flats are warmed by radiators (Heizkörper) under the windows. And yet, even now, Germans fling their windows wide open several times a day. "Why open the window when the heating is on?" you may wonder. There's a reason.

Stoßlüften — short and thorough

The heart of German airing is Stoßlüften, roughly "burst airing". Turn the radiator off, open the window all the way, swap the air for a few minutes, then close it again. Opening windows on opposite sides for a cross-draught (Querlüften) is even faster. Walls and furniture are still warm, so the room heats up again quickly once the window is shut.

The opposite is Kipplüften — leaving the window tilted open at the top. In winter it's best avoided: little air is exchanged, the wall around the window cools down, and the radiator keeps running while the warmth escapes.

The secret of the radiator numbers

Radiator valves usually show ❄ (or ✱) and the numbers 1 to 5. They don't mean "power" — they're a target temperature. 3 is roughly 20°C, 5 close to 28°C. So turning it up to 5 on a cold day doesn't heat the room faster; it just keeps going until the room is too hot. Set it once and leave it.

Why all the fuss? Mould

Cooking, showering, drying laundry — even breathing — adds moisture to the air. When warm, moist air meets a cold window frame or an outside corner, water condenses and mould (Schimmel) can follow. It's common in old buildings and in newly insulated, airtight flats. Tenants generally aren't obliged to heat, but they are often expected to prevent mould, and it can lead to disputes with landlords. It depends on your contract and your flat, so if you're worried, ask a tenants' association (Mieterverein).

Do	Don't
Open windows wide for a few minutes, several times a day	Leave a window tilted all day
Turn the radiator to ❄ while airing	Keep the heating on with the window open
Air right after showering or cooking	Open the bathroom door and spread the steam
Keep the space in front of radiators clear	Block radiators with sofas or curtains
Keep some heat on when you're out	Switch everything off so the walls get cold

How is my heating bill worked out?

In many flats you'll find a small meter on each radiator (Heizkostenverteiler). Its readings feed into the yearly service charge statement (Nebenkostenabrechnung); if you used more than you paid in advance, you pay the difference. Perhaps that's why thick socks and cardigans are standard indoor wear here. A cup of tea and five minutes of open windows — that's how a German winter starts.

Today's German words

Word	Meaning
lüften	to air, ventilate
das Stoßlüften	short airing with windows wide open
der Heizkörper	radiator
die Heizperiode	heating season
der Schimmel	mould
die Nebenkostenabrechnung	service charge statement

Tonight, open the window wide and wait five minutes — the air will feel fresh again. 🪟🧦