A well-insulated house only loses little energy if it is also airtight. This is precisely where the Blower door test on: It shows how airtight a building really is - and uncovers possible weak points. For building owners, planners and experts, the blower door test is a key building block for energy efficiency, comfort and building safety.
What is a blower door test?
The blower door test - also known as the differential pressure measurement method - is used to check the airtightness of the building envelope. The aim is to detect uncontrolled air leaks, which can lead to increased energy consumption and structural damage. The blower door test provides building owners, planners and energy consultants with a tool for assessing building quality and compliance with legal requirements.
Why airtightness of the building envelope is so important
A leaky building envelope has several negative consequences: Warm indoor air can penetrate into cold building components, where it can condense and cause moisture damage or mould in the long term. At the same time, heat escapes uncontrolled to the outside - this means unnecessary energy losses and higher heating costs. An airtight envelope, on the other hand, helps to reduce energy requirements, stabilise the indoor climate and prevent structural damage.
- Construction of the measuring system: A special fan is installed airtight in an outside door or window.
- Generation of a differential pressure: The fan generates a negative pressure (or alternatively a positive pressure) of usually 50 Pascal inside the building.
- Measurement of the air exchange rate: While the pressure is maintained, the system measures how much air is flowing in through leaks in the building envelope. The air exchange rate is calculated from this data.
Evaluation: The air exchange rate n₅₀ indicates how often the total air volume of a building is exchanged per hour at a pressure difference of 50 pascals. The result is compared with the limit values of SIA standard 180. For residential buildings with mechanical ventilation, the permissible value is generally n₅₀ ≤ 1.0 1/h. The lower the value, the better the airtightness.
Detect leaks - visibly and measurably
Even if a building passes the test mathematically, localised leaks can be problematic. This is why many experts combine the measurement with fog tests. Artificial fog is blown in - where this escapes visibly, there is a leak. Particularly critical points are window and door connections, roof transitions, sockets, pipe penetrations, component connections and transitions.
Such areas can then be specifically sealed - for a permanently functioning building envelope.
Is the blower door test mandatory?
Mandatory for:
- Buildings to Minergie-A or Minergie-P standard
- For larger buildings with more than 5 utilisation units or functional buildings
Recommended for:
- New buildings for quality assurance
- Energy-efficient refurbishments to check airtightness
We recommend the test as a valuable test tool to ensure the planned energy efficiency in practice.
Conclusion: Safety for your construction quality
The blower door test provides clear results on airtightness - and helps to recognise potential problems at an early stage. It protects your investment, improves living comfort and ensures long-term energy efficiency.