Blower Door Test FAQs

Here you will find frequently asked questions (FAQ) and help with all aspects of airtightness of building envelopes and the certified Blower Door test. Do you have further questions about professional differential pressure measurement in your building? Just write us a message via our contact form or call us directly. We're here to help!



What is a Blower Door test?

The Blower Door Test is a certified method for the reliable testing of airtight buildings. This is a so-called differential pressure measuring method. With modern technology, we calculate the air exchange rate at 50 Pascal between the inside and outside of a building with closed windows and doors.

How does a Blower Door test work?

The airtightness test can be carried out as soon as the building is completed. In order to guarantee the quality of an airtight building envelope, it is also advisable to carry out Blower Door tests at an earlier point in time. In this case, it is not an acceptance inspection, but a test for a high quality assurance.

On the agreed test date our technicians start with the installation of a calibrated differential pressure measuring system. For this purpose, an adjustable frame and an airtight panel are installed in an external door or window. With the help of a fan, a negative pressure of 50 Pascal is subsequently generated in the building. Leaks can get directly located.

50 Pascal corresponds to a wind force of 4 to 5. With a special Blower Door test software, the fan is controlled to check the air exchange rate. The volume flow on the fan is regulated with differently sized measuring orifices. After the negative pressure has been determined precisely, the positive pressure test follows.

What does the term airtightness mean?

The airtight level is assigned to the inside of the building envelope. An airtight building envelope has the important task of preventing heating air from leaking uncontrollably through joints and cracks in windows and doors. Moist air can as well enter through leaks and evaporate as thaw water. Especially in the winter months, molds are formed so quickly and the performance of the insulating materials used is lost in the long term. Brickwork, for example, is only airtight when plastered.

What are the advantages of a professional differential pressure measurement?

The professional airtightness test may only be carried out by a certified "airtightness tester according to DIN EN 13829 or ISO 9972".

The examiner performs the following tasks:

  • comparison of the requirements from the Energy Savings Regulation calculation and the thermal insulation certificate
  • recording the natural pressure difference in the building
  • leakage detection with a reliable statement on site
  • conducting a differential pressure measurement in accordance with the standard
  • preparation of a test report including leakage protocol

Is a Blower Door test mandatory for office buildings and industrial buildings?

As soon as a ventilation system is installed in the building, a Blower Door test must always be carried out. Otherwise there is a risk that the heat recovery of the ventilation system will not be taken into account.

But also for all other buildings a Blower Door test with a positive result is worthy. You will sustainably improve the annual primary energy requirement!

What should be considered for buildings without ventilation systems?

Even buildings without a ventilation system must be airtight. According to the current requirements of the German Energy Savings Regulation (EnEV), an air exchange rate of 50 Pascal (n50 value) of <3.0 l / h is required for this. In practice, however, it can be seen that most buildings already fall below the n50 value at <1.0 1 / h. In this case, the ventilation concept according to DIN EN 1946-6 should be checked at the start of construction. Possibly further ventilation measures, such as the installation of an exhaust system or window rebate ventilation is necessary.

How long does a Blower Boor test take in large buildings?

The actual measurement including leakage location usually takes two to three hours depending on the building volume. By contrast, the building preparation and installation of the ventilation technology is somewhat more extensive. In large buildings, several fans are used during the Blower Door test. The professional construction of six blowers can take up to two hours.

What should be considered when carrying out an XXL Blower Door test abroad?

  1. Firstly, we clarify the building parameters, such as the net volume and area of ​​the thermal envelope. This allows us to correctly calculate the number of units and transport right from the start.
  2. Our differential pressure gauges require a mains frequency of 220 volts and 50 hearts for trouble-free operation.
  3. Ideally, during the construction of the building sealing, it is discussed which parts are sealed. We keep this information in a report for you!
  4. Since there must be equal pressure in the building, we must also check in advance the exact installation locations for our measuring instruments.
  5. In advance, we discuss the weather conditions and features at the location with you. For large buildings, problems with natural pressure difference can occur even at wind force 2.
  6. We play safe: With the help of a modern infrared thermal imaging camera, we reliably detect leaks even on high-altitude components.

Who is allowed to carry out the certified airtightness test?

This is only possible with a certified auditor for building airtightness in the sense of the Energy Savings Regulation. Alternatively, the test may also be performed by an approved inspector in accordance with ISO 20807 "air-tightness testing".

Which devices does our rösemeier. team use for the Blower Door test?

For reliable results, we only use systems from the market leader Minneapolis Blower Door, because the devices are calibrated to ISO 9972.

And which devices are used for infrared thermography?

In building thermography, we work exclusively with the proven technology of the market leader Flir-Systems for exact measurements.

How much is a XXL Blower Door test?

The costs for an XXL Blower Door test were based on various factors, such as:  building volume, transport, number of blowers on site, sealing measures, etc. We calculate each offer individually based on a detailed conversation. Do not hesitate to ask for a general agreement, which contains a certain number of Blower Door tests for housing estates etc.

What values does the Blower Door test report contain and what do they mean?

The n50 value describes the air exchange rate at 50 pascals. This information provides information about the heated internal volume (V). The value is the air volume, which is exchanged per hour in the building at 50 Pascal pressure difference from inside to outside.

For the q50 value, the air permeability through the building shell at 50 pascals per hour is paramount.

In the Blower Door test report for buildings with a net volume of up to 1,500 m³, the evaluation is based on the n50 value. For larger buildings with more than 1,500m³ volume, according to Energy Savings Regulation requirements, the q50 value must be determined. Separately and independently, of course, both values ​​can be calculated on request.

These other important parameters are included in every Blower Door test report:

  • leakage current at 50 Pascal
  • natural pressure difference
  • flow coefficient
  • leakage coefficient
  • volume flow through the building envelope
  • evaluation of the leakage curve
  • condition of the building envelope including leak log

Which Energy Savings Regulation requirements for airtightness of buildings exist?

The Energy Savings Regulation requires the following airtightness values ​​for buildings with a ventilation system:

  • n50 value ≤ 1.5 1 / hq
  • 50 value ≤ 2.5 m³ / h x m²


For buildings without ventilation system, the following specifications apply:

  • n50 value ≤ 3.0 1 / h
  • q50 value ≤ 4.5 m³ / h x m²

What to do if the Blower Door test fails?

In this case, a detailed leakage log should be created that can easily identify air inlets or leaks. After eliminating these leaks, we recommend carrying out a new Blower Door test.