Why this happens here and not back home
Warm air holds water. When it touches a cold spot — a window corner, the wall behind a cupboard, the ceiling above the stove — the water comes out as tiny drops. Wet wall plus a few weeks equals black spots. That is Schimmel.
A normal family already puts a lot of water into the air every day from breathing, showers and drying clothes. Long Indian cooking adds more on top. It is not dirty cooking. It is just a lot of steam in a closed box.
Mould usually starts in autumn, when the heating goes on and the windows stay shut. That is right now.
The one number to watch: humidity
Buy a small hygrometer. It costs about as much as a kilo of basmati and shows the humidity in the room. Put it in the kitchen or the living room, not next to the stove.
- 40–60% — good. Relax.
- 60–70% — open the windows now.
- Above 70% for many hours — mould is coming. Change your habits this week.
Without a number you are guessing. With it, you know in ten seconds.
Air the German way: Stoßlüften
Germans have a word for it. Stoßlüften means opening the windows fully for a few minutes, not tilting them for hours.
- Open wide 3 to 4 times a day, for about 5 minutes in winter and 10 in autumn.
- Open two windows on opposite sides if you can. The air changes in minutes.
- Turn the heating down while the window is open, then back up.
- Do not leave the window on tilt (gekippt) all day. The wall around it gets cold and wet — exactly where mould loves to grow.
Habits in the kitchen that make the biggest difference
- Lid on. Dal, rice and chai with a lid put far less water in the air.
- Hood on, every time. If you have a Dunstabzugshaube, switch it on before you start and leave it on ten minutes after. Clean or change the filter — a greasy filter does almost nothing.
- Kitchen door closed, window open while you cook. The steam goes out, not into the bedrooms.
- After the pressure cooker, open the window for five minutes. That last whistle is a lot of water.
- Drying clothes inside? Use one room, keep its door closed and air it more. Or use the Keller or a Trockenraum if your building has one.
Heating and furniture
- Do not let rooms get too cold, even the ones you do not use. A cold bedroom is where the steam from the kitchen goes to die.
- Keep big furniture about a hand's width away from outside walls, so air can move behind it.
- Do not cover radiators with clothes or thick curtains.
If you already see mould
Take photos with the date first. Then:
- Tell your landlord (Vermieter) in writing — email is fine. In Germany the tenant has to report defects. If you hide it and it grows, you can end up paying for it.
- Small spots (smaller than a sheet of A4 paper, roughly): wipe with 70% alcohol (Isopropanol or Ethanol) and a cloth you throw away afterwards. Open the window and wear gloves.
- Do not use vinegar or bleach. Vinegar can make it worse on German plaster walls, and bleach only makes it look white.
- Bigger areas, mould that keeps coming back, or anyone at home with asthma or a baby: do not scrub it yourself. That is a job for the landlord and a professional.
Your Kaution. When you move out, landlords often blame mould on "wrong airing" and keep money from the deposit. Your best protection is simple: report early in writing, keep your photos, and keep your hygrometer readings. It shows you did your part.
Sometimes the problem is the building, not you — a cold wall, a leak, a bad window. If you air well, keep humidity in the good range and it still comes back, say so to your landlord. A Mieterverein (tenants' association) can help if you get stuck.
Things that actually help
These are search links, so you see all the options and today's price on Amazon.de. Prices change often, so compare a few before you buy.
- Digital hygrometerThe cheapest and most useful thing on this list. Get two if you can.See price
- Dehumidifier (Luftentfeuchter)For one problem room. Electric ones work best but use power — check the watts.See price
- Refill dehumidifier boxesNo power. Good for a small bathroom or wardrobe, too weak for a whole flat.See price
- Cooker hood filterLook up your hood model first so the filter fits.See price
- Isopropanol 70%For wiping small spots only. Buy the 70% kind, not 99%.See price
- Folding clothes drying rackPut it in one room with the door closed, and air that room more.See price
Als Amazon-Partner verdiene ich an qualifizierten Verkäufen. As an Amazon Associate I earn from qualifying purchases — you pay nothing extra.
Quick answers
What humidity is normal in a German flat?
Around 40 to 60 percent is good. If it stays above 70 percent for long, mould is likely.
Is it okay to keep the window on tilt all day?
No. A tilted window cools the wall around it and it gets wet. Open it fully for a few minutes, a few times a day, instead.
Should I use vinegar on mould?
No. On most German walls vinegar can make things worse. For very small spots use 70% alcohol. Bigger areas are for the landlord and a professional.
Do I have to tell my landlord about mould?
Yes. Tenants have to report defects. Do it in writing with photos, as early as possible.
Our food is worth the steam. With a hygrometer, a lid and five minutes of open window, you can cook the way you always did — and get your full Kaution back when you move.