‘Lüften’: How the German Technique Fits into Whole-House Ventilation

Mould growth is a common problem in homes, often triggered by poor ventilation and excess moisture. While quick-fix solutions like anti-mould paint or the German Lüften technique may offer temporary relief, they don’t tackle the underlying cause – ineffective ventilation that allows moisture to accumulate. To truly prevent mould and ensure your home remains healthy, comfortable, and energy-efficient, a comprehensive ventilation strategy is essential.

In this blog, you’ll learn:

• What the German Lüften technique is and whether it’s effective for UK homes
• The components of a whole-house ventilation strategy to prevent mould
• Practical steps you can take to improve airflow, moisture control, and building insulation
• How Lüften fits into a broader approach to healthy home ventilation

The German ‘Lüften’ Technique: Does it Work?

The German concept of ‘Lüften‘ (which translates to ‘airing out’) is often recommended as a simple, effective way to reduce indoor humidity levels. It involves opening windows at intervals to allow fresh air to circulate, replacing stale, humid air with drier outdoor air.

While this technique can be useful in some homes, it has significant limitations:

• Homes with poor insulation may lose too much heat.
• Many homes in the UK, especially flats, lack sufficient window openings for effective ventilation. In fact, tenants in social housing flats are more than 11 times more likely to experience ventilation issues than plumbing issues.
• Air exchange may not be enough in high-occupancy households.
• External factors like traffic noise, security risks, and winter weather can make Lüften impractical.

Relying solely on natural ventilation overlooks the need for a properly designed and compliant whole-house ventilation strategy.

How to Create a Mould-Free Home: Whole-House Ventilation

A well-designed ventilation strategy should match a home’s size, layout, and occupancy levels. Here’s what to consider:

Ventilation in Wet Rooms (Bathrooms and Kitchens)

• Intermittent extractors – extractor fans ensure moisture is actively removed from humid areas.
• Mechanical ventilation (centralised or decentralised).
• Mechanical ventilation with heat recovery (MVHR) – Retains warmth while replacing stale air.

Background Ventilation

• Trickle vents and passive vents – Controlled airflow to prevent stagnation.
• Air infiltration – Some older homes rely on  uncontrolled air leakage through gaps and cracks for ventilation (not ideal). 

Cross Ventilation

• Can windows be opened on different sides of the home? Allows air movement.
• Are there adequate undercuts beneath internal doors? Ensures airflow between rooms.

Purge Ventilation

• Fully opening windows for rapid air exchange (where feasible).
• Consider barriers (e.g. traffic noise, security concerns).

Even with the best ventilation system, occupant behaviour plays a crucial role. A household of four can generate up to 20 litres of moisture per day through cooking, showering, drying clothes, and even breathing.

Simple actions such as opening windows in the morning for purge ventilation can help, but this is not always feasible – particularly in single-aspect apartments where cross-ventilation is impossible. This is why a comprehensive ventilation strategy is necessary to control humidity levels and prevent condensation.

Improving Building Fabric to Reduce Condensation Risk

Since condensation forms on the coldest surfaces in a home, insulation continuity is vital. Poorly insulated areas can become cold spots, increasing the likelihood of condensation and mould. 

Before insulating a property, a trained thermographer can conduct a thermal imaging assessment to identify surfaces at risk of condensation and recommend targeted improvements.

Read more about how cold spots contribute to mould growth:

Heat Loss Survey Commercial Heat Loss Surveys

Cold Spots: Causes, Consequences, and How to Fix Them

Read Article

What’s Next?

Mould prevention requires a multifaceted approach that combines ventilation, insulation, airtightness, and occupant awareness. 

While Lüften can be helpful, it is not a standalone solution – especially in homes where controlled ventilation is limited. Preventing mould requires a whole-house approach that considers building design, ventilation efficiency, and insulation quality.

We specialise in building energy performance, including ventilation testing and air tightness assessments. Whether you’re a homeowner or a housing provider, we can help you create healthier, mould-free living spaces. For expert guidance on ventilation and building performance, get in touch with us today.