Ten years after the first Blower Door Test in BAC

In 2010 BAC was the first company in Catalonia and one of the first in Spain to acquire equipment for carrying out Blower Door tests, an air tightness test that is also called the Minneappolis Blower Door Test.

This type of test, increasingly requested by customers, and our experience of more than 10 years conducting it in multiple buildings and spaces, has positioned us as one of the benchmarks in this area.

The test was created in Minneappolis (US) by the TEC Company – The Energy Conservatory at the beginning of 80s, and was imported to Germany as the first place to be introduced in the North of Europe in 1989 through the BlowerDoor GmbH. In 1991 was developed the first test of Zero Energy in Dörpe, Germany.

In 2007, 7 red fans were connected to carry out the test on an office area of 90,000.00 m2. Since then the use of this test has continued to grow throughout Europe from North to South.

The objective of the test is to be able to evaluate and detect uncontrolled air leaks through the building envelope. The test consists of performing a depressurization and pressurization of the building using a fan that is installed in the door. It starts at 70Pa and gradually decreases until it reaches 25Pa in steps of 5Pa. The air renewal rate will be the average of the measurements obtained between depressurization and pressurization. All this process is explained in the norm.

The air renewal rate, n50, measures the air renewals that are needed, which differs in:

  • The rate should be n50 ≤ 3.0 m³ / h in the case of buildings with manual ventilation.
  • In the case of buildings with mechanical ventilation systems, the limit becomes n50 ≤ 1.5 m³ / h.

In Spain today there are no mandatory regulations regarding this area. However, references to the recommended values for a single-family building are found in the Calener GT reference manual (currently a recognized non-current document):

  • High level of tightness: less than 4.
  • Average level of tightness: between 4 and 10.
  • Low level of tightness: greater than 10.


Finally, the test based on various parameters and the results obtained, determines the energy classification (between A and G).

At the same time to the Blower door test, we also carry out the inspection or detection of leaks, which consists of creating a 50 Pa depression in a short time. This is achieved by implementing a fan connected to a computer and assembled in an adjustable frame that replaces the access door to the space, also using different pressure sensors. In this way a pressure differentiation is created with the exterior that maximizes the filtrations within the test space.

In this phase, the filtration points are determined from detection instruments such as smoke test, thermography or anemometer This inspection is manual, observing the perimeters of windows and doors, where possible infiltrations can appear.

This test allows evaluating the execution of the enclosures of any room or closed space, in order to optimize energy consumption for to air-condition the space. It also allows quantifying the added cost of these leaks due to the renovations that must happen due to the inefficiency of the current system. Through the non-destructive tests used, it is possible to quickly determine the leakage points and thus where to repair them and thus achieve better energy efficiency.