The Blower Door Test Measurement of airtightness

Anyone constructing a new building is faced with all sorts of questions and technical terms that are not self-explanatory. THE Blower-Door-Test is one of these terms. Manufacturers should know and understand this test. If you want to live comfortably in your new home and save energy at the same time, you need the building’s exterior cladding to be as airtight as possible. The Blower Door Test determines air tightness. At this point we will explain what lies behind the Blower Door Test, how it is carried out and what advantages it offers you.

What does “blower door test” mean?

The Blower Door Test can be easily summarized with the term “Airtightness measurement“or even”Differential pressure measurement method«. It thus provides information about the airtightness of a building. Very few people know that the name «Blower Door» actually comes from a manufacturer that offers measuring devices for measuring airtightness. However, the name has established itself in the industry and is now generally used to name the measurement method.

How does the airtightness measurement work?

To carry out the «blower door test» 5 steps are necessary, which we explain below.

Step 1: Seal the building

To determine how airtight a building is, all windows and doors must first be closed. If you have decided on an air conditioning version for your new building, you need to turn it off for the Blower Door Test and also seal it. Otherwise the measurement results would be distorted.

Phase 2: Using the “blower door”

Today, the eponymous “blower door” is used: the metering service provider spreads a kind of canvas with a circular opening in one of the external doors, usually the front door. The opening is adapted exactly to the dimensions of a fan placed in this position.

Step 3: Airtightness measurement

Only now is the real thing happening Airtightness measurement of the building. This is a slightly more complex process where the metering service provider first measures the pressure difference with the fan switched off. With the fan activated, various pressure points are then brought closer together and the volumetric flow rates are measured. Finally, the natural pressure difference is measured again. For this reason the Blower Door Test is also called differential pressure measurement.

Measuring the airtightness of the building is a complex process in which the pressure difference is first measured when the fan is deactivated. With the fan activated, various pressure points are then brought closer together and the volumetric flow rates are measured.

Messaphase 1

As soon as the inspectors put the fan into operation, a constant negative pressure of around 50 Pa is created in the building in the first measurement phase. This is necessary because the fan can only draw in air through leaks in the building using negative pressure.

Messaphase 2

In the second measurement phase the negative pressure is gradually increased up to 100 Pa.

Messaphase 3

In the third and final measurement phase, an overpressure is finally generated and all measured values ​​are recorded again as in the negative pressure measurement. This way you can identify leaks, also called leaks. This can happen in very different ways. Some leaks, such as leaky windows, can sometimes even be felt with your hands. In addition, technical devices are used. Flow meters, thermographic cameras or nebulizers help make leaks visible. Once losses are identified, this is a very important step for traders to eliminate them.

Messaphase 4

Finally, the natural pressure difference is measured again. For this reason the Blower Door Test is also called differential pressure measurement.

Step 4: Evaluation of the measured values

All of this serves the purpose Determination of relevant measured valueswhich are important, for example, if you want a ventilation system in a newly built house to work efficiently. The most important value is the limit value for the air exchange rate n50. Limit values ​​in the German construction industry are regulated by DIN standards. By today’s standards, a new building must have a planned, seamless level of sealing between the exterior and interior. Play while you do it Thermal bridges AND Thermal insulation a great role.

Step 5: Fix the vulnerabilities and test again

Ideally two tests are performed: The Blower Door Test in the shell state reveals leaks which can usually be eliminated without problems because the sealing level is easily accessible. A second measurement in the habitable house it provides the required values ​​for the EnEV.

Why is it mandatory to perform the Blower Door Test?

In fact, airtightness measurement is mandatory if a new building is being built and the test is carried out in… EnEV proof is provided. Or if you have decided on a ventilation system for your new building that takes the energy balance into account. Even with some financing programs, such as KfW, the Blower Door Test is mandatory.

What does the differential pressure measurement method involve?

It is important to understand that measurement does not just provide some values ​​for shape. Rather, it provides information on the quality of construction. Thermal bridges, external insulation, windows, doors – Only when all activities and materials work together optimally will it be possible to create an energy-efficient building. Leaks that go undetected are a real nuisance for building owners because they lead to energy losses. They can also cause structural damage if moisture penetrates. The Blower Door Test is practically essential for the efficiency of a ventilation system. Once in operation, the system should not draw in fresh air through leaks as this has a direct impact on heat recovery and air quality.

Who can carry out such a test?

If you yourself, as a builder, are an expert and have the appropriate equipment, you can theoretically carry out the test yourself. We recommend that you have your home tested for airtightness by a certified professional. Rötzer’s measurement service providers are extremely experienced experts who have already performed hundreds of Blower Door tests. Here you can rely on the use of calibrated devices and the precise evaluation of the results. You can also find certified suppliers on the Construction Air Tightness Trade Association website.

How much does the Blower Door Test cost?

The costs for a Blower Door Test are absolutely manageable as part of your new building budget. They lie between 350 and 500 euros. Compared to the advantages of the test, this is an investment that manufacturers should not give up. Check the supposed savings offers carefully. Especially if Financing are at stake, the selection of the metering service provider is of utmost importance. A certified supplier will carry out the test within the indicated price range and document it so that the results are recognized as part of a financing program.