What you should know about air tightness testing

The most people have already heard about an air tightness test for dwellings but do not have a certain knowledge, to value the quality of the test and the results, they got.

Even the certified air tightness tester scheme here in Ireland, provided by NSAI, is (unfortunately) not a guarantee for a qualified and genuine air tightness test. 


I´d like to point out some details subsequently, which are essential for a serious air tightness test:


1. Weather during the test

For an accurate test result it is important to have as less wind as possible during the air tightness test as well as almost similar temperatures between inside and outside.


2. Building dimensions

The air tightness tester has to double check the building dimensions on site, in case they got provided by a third party. A comprehensible calculation of the floor area, building volume and building envelope area has to be part of the test report.


3. Duration of an air tightness test

Coming from my experience, a formal test in compliance with the test standard (ISO 9972) takes at least 2.5 hours for a (very small and straight forward) dwelling. Bigger houses with irregular shapes will extend the test. A two storey with 200m² can take up to 5 hours for a qualified air tightness test.


4. The right building phase for an air tightness test

The official test standard (ISO 9972) separates two different tests - the preliminary and the final. The preliminary test is a quality control for the installed air tightness layers and should be performed right after the installation work, to allow adjustments and improvements. The final test has to be done when the house is finished. Finished means nothing else than the majority of construction works is finished and the house is more or less ready to move in. If the house is not finished, the test can´t be declared as a final test.


5. Detection of existing leakages during the test

Surprisingly, not every NSAI certified air tightness tester is performing a leakage detection prior to the official depressurization & pressurization test. That´s not compliant with the official standard!


6. Range of building pressures for an air tightness test

I´ve seen many air tightness test reports with the required quantity of data points but the most of them have just readings for higher differential pressures. The air tightness test standard is clearly setting the lowest limit for the data collection: "The minimum pressure difference reading shall be 10 Pa or five times the zero-flow pressure difference." 

It´s more difficult and time consuming to measure at lower pressure differences, that´s why some testers do finish their air tightness readings  always at around 20-30 Pa differential pressure.


7. Manipulations

There´s plenty of options to manipulate an air tightness test, wittingly or unwittingly. It starts with wrong building dimensions and ends in manipulating the fan. I do not want to provide details of how to manipulate an air tightness test, because I´m always aiming for accurate tests and results. There´s no advantage of having a better air tightness test result in the report than in reality.

8.Official standard for air tightness testing

Here in Ireland, the air tightness test has to be performed on the base of the latest official standard (I.S.) ISO 9972. The European norm EN 13829 for air tightness testing is not longer valid for testing and can't be used or declared for the test or in the test report. 


If you´re in need of an air tightness test or in case you might have doubts about the readings of an existing test, please feel free to get in contact with me, to discuss how you can be supported.