Consumer champion Which? has shared a simple German ventilation hack to tackle damp, which is a simple and affordable method that helps fight off any mould in your property
Winter is often the worst time of the year for damp and mould in affected homes. Caused by excess moisture, the problem is exacerbated when the temperature drops and people spend more time indoors with the windows and doors closed. However, people have now been left stunned after learning about a ‘free’ method that helps to banish and prevent mould growth in your home in five minutes.
Which?, the UK’s leading consumer advocate that evaluates products and services, has brought the technique to public attention through social media. The organisation posted a video on Instagram showcasing the German Stoßlüften method to fight off and prevent mould, which requires opening every window in your property for five minutes, two times a day.
The term Stoß means ‘shock’ while lüften translates to ‘ventilation’, making this a shock ventilation strategy. It represents an inexpensive, straightforward and accessible solution for addressing mould issues within your property.
During the Instagram video, the Which? representative explaining Stoßlüften remarked: “Have you got a damp house? Well this is what the Germans would do about it and it’s basically free.
“Some ways of conquering damp can be expensive or require a fair bit of DIY. Germans have a great habit that anyone can get into: Stoßlüften, literally shock ventilation.
“Wrap up warm, run around the house and open all your windows wide for five minutes twice a day. Yes, even in the freezing cold!”
The presenter elaborated: “The warm, damp air in your home will quickly get replaced with cold, dry air. When you’re sealed back up again the temperature should quickly get back to comfortable but now the moisture in the air is banished and won’t be condensing in damp patches on your walls and windows.”
The post was captioned: “This simple German hack will help you tackle damp and mould without spending a penny.”
The Instagram clip has garnered 3.5 million views, 37,000 likes and close to 1,000 comments, as people shared their bafflement by how easy the hack was.
One viewer remarked: “What great advice. I have a German/Dutch brother in law and a very good German friend and they always sleep with the bedroom window open.”
Someone else chimed in: “The lung clinic at my chronic asthma hospital team also recommend this – get them windows open!” A third person who’s tested the method wrote: “Done this for years, in a council block, that has huge issues with damp and mould. Works perfectly and really is a life saver.”
Numerous Instagram users sharing their experiences in the comments revealed that Stoßlüften has proved effective for themselves or relatives who’ve given it a go. A cottage dweller explained: “I open my windows every day all year. I live in a very old cottage with no damp proof course. And no damp at all inside. So it works. I’ve always needed fresh air. Glad I’m doing something right.”
That said, a number of UK-based Instagram users expressed doubts about its effectiveness in Britain. One pointed out the “air in England isn’t dry, it’s damp, especially at the minute”.
This sentiment resonated with many others.
Another user disputed this claim, offering clarification: “A lot of people in the comments seem to mistakenly believe that the cold air outside their house is as humid (or even more humid) than the warm air inside their house. This isn’t true: cold air has a much lower carrying capacity: it can’t hold as much water vapour as warm air.”
They continued: “When you open your windows, the dense cold air flows into the house replacing the less dense warm air (which is driven outside). This means that you have replaced warm air with a high moisture content with cold air with a lower moisture content.”
The explanation went on: “As that cold air warms up inside your house it absorbs moisture from surfaces and materials. Doing this multiple times a day will therefore move moisture from inside your house to outside your house.”
Which? then posted a follow-up video addressing viewers who argued that Britain’s damp climate would render window opening ineffective against mould.
In the clip, their spokesperson described this as a “confusion between relative humidity and absolute humidity”.
Using a visual aid of two water glasses – one small and filled to the brim, another larger but containing less liquid – he illustrated the concept.
Gesturing to the smaller vessel, he explained: “This very full glass is like the air outside on a cold day. It’s at 95% capacity. It is holding as much water as it’s capable of holding but warm air can actually hold almost twice as much in a house compared to the cold air outside.”
