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Blower Door test - why is it necessary?

When building a house, everyone seems to understand the concept that the building must have good thermal insulation and waterproofing. If a builder builds a house with a leaking roof, it is immediately clear to everyone that something is wrong with the building. On the other hand, unfortunately, only a few think about the importance of the air tightness of the building. After all, uncontrolled air movements through the building shell are not as clearly visible as a leaking ceiling... And the owner of the building will not be able to boast of an airtight house in the same way as with the most expensive Italian tiles...


Blower Door is setup by technician

The airtightness of the building is extremely important if we want to build an energy-efficient building. Not to mention achieving CO2 reduction targets. According to various sources: 40% of CO2 emissions come from buildings. 70% of energy in buildings is said to be used for heating and cooling. Other studies reveal that 30-70% of the energy used to heat or cool buildings is lost directly due to uncontrolled air leaks. Leaky buildings cannot be energy efficient!

Chart explaining about CO2 emisions from buildings and energy usage in buildings

The Blower Door test is a test method that shows the amount of air leakage through the building structures at a certain pressure difference in the interior versus the atmospheric pressure. A door with a fan is installed in one of the exterior door, where the fan supplies such an air flow as to maintain a certain test pressure. Typically, this pressure amounts to 50Pa rarefaction or overpressure. The fan is calibrated and based on the pressure difference and fan rotation speed, the air leakage is calculated, which is most often expressed as air changes per hour at the test pressure. By using the Blower Door test method together with thermal imaging and a smoke generator, largest areas of leakage can be detected.


Graphically shown typical air leakages in the house

First, energy efficiency. Even with very thick and effective thermal insulation, a lot of energy will be lost through leaks. Leave the door of the refrigerator open and observe that it never shuts off - it works continuously consuming tremendous amounts of energy. The temperature difference in heated rooms creates the so-called chimney effect - warmer air always tries to break out in the upper part, creating an influx of cold air at the lower level of the building. Uncontrolled air exchanges, of course, also occur under the influence of wind. It is generally accepted, that test pressure of 50Pa simulates effects of windspeed of 10 m/s.


Second, the longevity of building structures. Moisture moves primarily in the form of vapor with air currents rather than by diffusion through materials.

Comparison of how moisture is transfered-  diffusion vs air leacage

In our conditions in the Baltic states, the source of moisture typically is indoors - we exhale, work in the kitchen, bathe, wash clothes, etc. - all these activities saturate the air with a large amount of water. This is the reason we put vapor barrier “on the warm side”. Normally, we exchange air with ventilation equipment. But if there are leaks in the structure through which this moist and warm air enters the structure, there is a high risk of condensation on the cool surfaces. And then already wet constructions themselves become a cold bridge, because wet insulation dramatically loses its properties. Mold and structural damage are often observed in such places.


Thirdly, all the other reasons – hermetic buildings are quieter, there are no easy paths for insects, street dust does not enter the premises, and smells does not propagate from apartment to apartment. In a hermetic building, it is possible to properly adjust the heating and ventilation systems - their operation mode is minimally affected by changing weather conditions.

Blower Door installed and ready for testing

The Blower Door test allows the potential buyer of the house to verify the quality of the construction of the building - the tighter the building, the more attention the builder has paid to the construction of various nodes - correctly installed and high-quality windows, high-quality installed vapor insulation, etc. Unfortunately, we often hear stories that new construction does not even come close to meeting the energy efficiency goals set. Everything looks great on "paper", but the operating parameters differ greatly. The most common reason for such a scenario is precisely the leakage of the building. This clearly shows that there is need to make air tightness test mandatory. Many countries have already introduced a requirement for mandatory building air permeability testing, which forces to build with higher quality.


With many specialists involved in the construction process - window assembly, electrical installation, ventilation, heating system, insulation installation, sewer construction, water supply construction, finishing works - the responsibility for the airtightness of the building is shared. And wherever there is shared responsibility, there is no accountability… until now.


Our company offers building sealing works with the revolutionary AeroBarrier technology. We offer our customers a building air tightness test (Blower Door test), as well as building sealing. AeroBarrier takes the guesswork out of what level of impermeability will be achieved. Guaranteed!


We invite you to familiarize yourself with AeroBarrier on our website!


Warm greetings,

AirSealing.EU team,


SIA Line-X Baltic

Čuibes iela 7, Rīga, LV-1063

+371 27701135

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