Stop condensation and mould in winter: the German airing routine, plus UK and US advice

Open windows wide for about 5 minutes two or three times a day instead of leaving them tilted, air the kitchen and bathroom straight after cooking or showering with the door shut, and keep humidity between 40 and 60 percent.

By Abu Bakar SaadatPublished 28 October 20263 min readPublisher: Saadat Rafiq

Illustration

At a glance

Airing in winter (UBA): Windows wide open 2 to 3 times a day, about 5 minutes per room
After cooking or showering: Window wide open 5 to 10 minutes, door shut
Humidity: 40 to 60 percent (UBA); ideally 30 to 50 (EPA)
Clean it yourself only if: Under about 0.5 m² (UBA) or 10 sq ft (EPA)
Advice from: Umweltbundesamt, Centre for Sustainable Energy and US EPA, read 27-28 October 2026
Checked: October 2026

Germany, the UK and the US side by side

	Germany (Umweltbundesamt)	UK (Centre for Sustainable Energy)	US (EPA)
Airing	Windows wide open 2 to 3 times a day, about 5 minutes per room in winter; never left tilted	Open windows regularly, keep trickle vents open, use extractor fans	Vent dryers and stoves outside; use exhaust fans
Humidity	40 to 60 percent	Check rooms with a hygrometer	Below 60 percent, ideally 30 to 50
Clean it yourself if	Under about 0.5 m², surface only, and you're not allergic or ill	Treat it with a mould spray containing bleach, covering an area 1 m wider than the patch	Under about 10 square feet (3 ft × 3 ft)

Step 1: spot condensation mould

Illustration of water droplets on a window pane running onto the frame, with small dark dots in the corner — Illustration

Condensation is the most common cause of damp. You can recognise it by small black dots near cold surfaces like window frames (CSE). It happens when warm, moist air from showering, cooking, drying laundry and even breathing meets a cold wall or window.

Step 2: air the German way (Stoßlüften)

Illustration of a room with windows on opposite walls both open wide and air flowing straight across — Illustration

Open several windows wide for a short time, ideally on opposite sides of the home so the air flows straight through. In winter, 2 to 3 times a day for about 5 minutes per room is enough. Air the bedroom for 5 to 10 minutes after you get up. Don't leave windows tilted: it wastes heat and cools the wall by the window, which can lead to mould (Umweltbundesamt).

Step 3: kitchen: lid on, door shut, window open

Illustration of a pan with its lid on, the kitchen window wide open and the kitchen door closed — Illustration

Keep lids on pans (CSE). Open the window wide while you cook and for 5 to 10 minutes afterwards, and keep the kitchen door shut so the moisture doesn't spread through the home (Umweltbundesamt).

Step 4: bathroom: wipe the walls, then air

Illustration of a hand pulling a squeegee down a wet shower wall, with the bathroom window open — Illustration

Straight after a shower, wipe the water off the walls and floor; the Umweltbundesamt suggests a window squeegee. Then open the window wide for 5 to 10 minutes with the bathroom door shut. Use the extractor fan every time there's steam and keep it clean (CSE).

Step 5: check the humidity

Illustration of a woman pointing at a small round hygrometer on a shelf with the needle in the middle band — Illustration

A cheap hygrometer shows which rooms need more airing (CSE, Umweltbundesamt). Aim for 40 to 60 percent (Umweltbundesamt). If it stays high, a dehumidifier helps in severe cases (CSE).

Step 6: move furniture off cold walls

Illustration of a woman beside a wardrobe standing a little away from the wall, with air rising behind it — Illustration

Mould often grows on outside walls, in corners and behind or under beds and big furniture (Umweltbundesamt). Pull furniture away from the wall so air can circulate behind it (CSE). Keep the doors of cooler rooms, like bedrooms, shut so warmer, moister air from the rest of the home doesn't condense there (Umweltbundesamt).

More that helps

Laundry: dry it outside if you can. Otherwise, run the spin cycle twice, use a tumble dryer, or hang it in a room with the door shut and the window open (CSE, Umweltbundesamt).
Heating: in cold weather, put it on often enough to keep the home dry. It may need a service, or the radiators may need bleeding (CSE). See how to bleed a radiator and how to top up boiler pressure.
No portable gas heaters indoors: CSE says they make the air very moist.

If this doesn't work

The mould keeps coming back: the moisture source is still there and has to be fixed (Umweltbundesamt). The damp may be coming in from outside (penetrating damp, often worse when it rains) or rising from the ground. If you can't find the cause, get a damp specialist to survey the home (CSE).
A large patch, or you have allergies, asthma or a weakened immune system: don't clean it yourself. Use a professional (Umweltbundesamt, EPA).
You rent: tell your landlord. In Germany, tenants' associations (Mietervereine) and some health offices (Gesundheitsämter) give advice (Umweltbundesamt). In the UK, Citizens Advice can help.

Questions readers ask

Is it better to leave a window tilted open all day?

No. The Umweltbundesamt says windows left tilted for a long time push up heating costs and cool the wall beside the window, which can cause mould. Open them wide for a few minutes instead.

What humidity should my home have?

The Umweltbundesamt says between 40 and 60 percent. The US EPA says below 60 percent, ideally 30 to 50. A simple hygrometer shows it.

Can I clean mould off myself?

Small patches, yes. The Umweltbundesamt says under about 0.5 square metres of surface mould, and only if you are not allergic to mould and have no chronic airway illness or weakened immune system. The EPA puts the limit at about 10 square feet. Larger patches need a professional.

Why does mould keep coming back?

Because the moisture that feeds it is still there. The Umweltbundesamt says the cause must be found and fixed, or the mould returns.