Air leakage detection methods – which techniques are used?

Air leakage detection is an essential part of airtightness testing. It helps identify leaks in the building envelope at an early stage and investigate their causes. Different techniques are used depending on the task, and several methods are often combined to provide reliable evidence of leakage.

Feeling air leaks

The simplest method is to feel airflow by hand during a BlowerDoor test.

Particularly with larger leaks around windows, doors or connections, incoming airflow can often be detected without additional tools. Even this simple technique forms part of systematic air leakage detection.

Measuring airflow

A thermal anemometer can detect even low air velocities.

The instrument measures airflow velocity and is particularly suitable for examining gaps, connections and penetrations. However, measured values must always be assessed in relation to the size, geometry and location of the leak.

Visualising leakage paths

Fog is particularly useful for making airflow paths visible.

Fog is introduced deliberately under negative or positive pressure. This makes it possible to trace airflow and visualise, for example, odour migration routes or leakage paths between different parts of a building. Applications include investigating odour problems or reconstructing an “ant trail”.

Locating leaks using ultrasound

In the ultrasound method, a transmitter emits high-frequency sound waves, which are detected by a receiver on the other side of the building envelope. Depending on the transmitter's position, leaks can be investigated from inside or outside.

The method is particularly suitable for windows, doors and glass façades. However, it has limitations when leakage paths are complex or winding. Modern systems can even provide a visual representation of the ultrasonic signals.

Thermal imaging visualisation

Detecting airflow with thermography is based on the fact that moving air changes the surface temperature of building components. Thermography cannot show the air itself, only the temperature changes it causes. In building physics, thermography is therefore generally combined with a BlowerDoor test: the fan creates negative or positive pressure inside the building. Incoming or outgoing air cools or warms wall surfaces, and the resulting temperature differences can be seen and documented in the thermal image. A BlowerDoor test helps distinguish air leakage from other defects.

Conclusion

Various techniques are available for detecting air leaks. The choice depends on the question being investigated and the building conditions. In practice, several methods are often combined to locate leaks reliably and determine their causes clearly.

Frequently asked questions about air leakage detection methods