Air Tightness Testing is the process of measuring the amount of conditioned (heated or cooled) air entering and exiting a building through uncontrolled infiltration
A calibrated fan is installed into the external envelope of the building and supplies air into, or extracts air out of, the property creating a controlled building pressure differential. The tester uses calibrated equipment and calculates an air flow into, or out of, the property. In simple terms, the amount of air going into, or out of the property when the building is subject to a pressure differential is the amount of ‘air leakage’.
The results for air tightness tests can be presented in three different ways
Air Leakage, known as ‘Qpr’, is the amount of air entering or exiting the building at a given pressure.
In most countries, Q50 is used to denote the air leakage at a building pressure differential of 50 Pa. Units are m3.h-1 @ 50 Pa.
Air Permeability, known as ‘APpr’, is the amount of air leakage divided by the internal envelope area of the building.
In most countries, AP50 is used to denote the air permeability at a building pressure differential of 50 Pa. Units are m3.h-1.m-2 @ 50 Pa.
Air Changes per Hour, known as ‘Npr’, is the amount of air leakage divided by the internal volume of the building.
In most countries, N50 is used to denote the air changes per hour at a building pressure differential of 50 Pa. Units are m3.h-1.m-3 @ 50 Pa.
ATTMA Members are required to use ATTMA Lodgement which automatically creates their certificate (see image to the left)
For a testing organisation to show compliance with this standard they shall carry out their testing in an equitable manner and must remain independent of companies involved in the construction of the buildings they test. They must also have suitable third party monitoring systems in place and this is demonstrated by either having an active membership with a CPS scheme, such as ATTMA or hold accreditation to ISO/IEC 1705:2017, or later