Stop mould this winter: daily airing routine + humidity checker
Many desi families find out about mould the hard way. The first months feel fine. Then, around January, a black spot shows up in the bedroom corner or behind the wardrobe.
It's not because your flat is dirty. German flats are built to keep heat in. The windows close very tight. That's great for your heating bill, but the moisture from cooking, showers and drying clothes has nowhere to go. It sits on the coldest wall and turns into mould.
The good news: you don't need expensive machines. A few habits and one small gadget do most of the work.
Why our kitchens make more moisture
Desi cooking is great, but it's steamy. Dal, rice, chai twice a day, a pressure cooker whistle — all of it puts water into the air. Add a family breathing at night and clothes drying in the living room, and the air gets wet fast.
We wrote a full guide just about the kitchen side: Indian cooking and mould in a German flat. This page is about the daily routine for the whole flat — and how to check your numbers.
"Stoßlüften" — the German way to open windows
Your German neighbours will tell you about this, and they're right. Stoßlüften means opening the window fully for a short time — not leaving it tilted (gekippt) all day.
- Turn the radiator knob down.
- Open the window wide. If you can, open a window on the other side too, so the air moves through.
- Wait about 5 minutes in winter (a bit longer in autumn and spring).
- Close the window and turn the heating back up.
Do this 3–4 times a day: morning, after cooking, after showers, and before sleep. A tilted window all day cools down the wall around it — and cold walls are exactly where mould grows.
How warm should the rooms be?
Saving on heating is smart, but don't let any room get too cold. German consumer advice centres say rooms should not drop below about 16 °C. A rough guide:
- Living room: about 20 °C
- Kitchen: about 18 °C
- Bedroom: about 16–18 °C
Keep doors closed between warm and cold rooms. If you open the bedroom door to "share" heat from the living room, the warm wet air goes into the cold room and sits on the walls there.
Also leave a small gap (about a hand width) between big furniture and outside walls, so air can move behind it.
The one gadget worth buying: a hygrometer
You can't see humidity. A small digital thermo-hygrometer shows you the temperature and the humidity in the room. Consumer advice centres say a simple model is enough — you don't need an app or Wi-Fi.
How to read it:
- Below 40% — the air is dry. Fine for walls, but your skin and throat may feel it.
- 40–60% — good. Keep doing what you're doing.
- Above 60% for hours — air out the room now.
- Above 70% often — real mould risk. Air out more, and check where the moisture comes from.
🔍 Free humidity checker
Type the numbers from your hygrometer. Nothing is saved or sent anywhere.
What this checker can and can't tell you
It gives a simple traffic-light answer based on common advice (40–60% humidity, rooms not below about 16 °C). It can't see inside your walls, it can't tell you if the building has a damp problem, and it's not a legal or health opinion. If mould keeps coming back even though you air out well, talk to your landlord.
🛒 The small winter kit
These links open the Amazon.de search, so you can compare prices and reviews yourself.
Shows room temperature and humidity. The most useful one.
Keeps cold air out of warm rooms.
For wardrobes and small corners. Helps a bit — doesn't replace airing out.
Wipe the wet glass in the morning, before the water runs into the frame.
Found a black spot? Do this
Small spot, smooth surface (like a window frame or tiles): wear gloves and a simple mask, open the window, and wipe it with 70–80% alcohol (Ethanol or Isopropanol from the chemist). Then dry the area.
Don't use vinegar on walls. On some wall types it can make things worse. And don't just paint over it.
Bigger area, or it keeps coming back: tell your landlord (Vermieter) in writing — an email or letter is fine. Add a photo with the date. In Germany, tenants have to report defects like mould without delay. If you wait too long, it can cause trouble later with the deposit.
If you're unsure about your rights, the local tenant association (Mieterverein) can help for a small yearly fee.
Kids' rooms and baby rooms
Don't overheat a child's room — around 16–20 °C is fine. Air it out while the child is in another room. Don't put the bed or cot right against a cold outside wall.
✅ Daily winter checklist
Tick it off each day. Print it and stick it on the fridge.
Common questions
Is a tilted window (gekippt) enough?
Not really. It lets out heat all day but changes the air very slowly, and it makes the wall next to the window cold. Open fully for a few minutes instead.
Should I buy an electric dehumidifier?
Most flats don't need one if you air out well. They cost money to buy and to run. Get a hygrometer first and see your numbers for two weeks. If the humidity stays high even with good airing, then think about it — or talk to the landlord.
Will airing out raise my heating bill?
Short, full airing loses much less heat than a window tilted all day. The walls and furniture stay warm, and the room heats up again quickly.
Who pays if mould comes back?
It depends on the cause — the building or how the flat is used. That's why reporting early, in writing, with photos, matters. For your case, ask the Mieterverein.
One last tip: start this in October, when the heating first goes on. It's much easier to stop mould than to get rid of it.
New in Germany? Our first winter guide covers clothes, shoes and what to buy. Worried about the bill? Try the heating CO₂ calculator.
Share this with a friend who just moved to Germany — it'll save them a cold, black-spotted January.
Als Amazon-Partner verdiene ich an qualifizierten Verkäufen.
This post is general information, not legal or health advice. Tips are based on public advice from German consumer advice centres (Verbraucherzentrale).