Air Permeability refers to the amount of air that will travel through a window or door system in its closed position. Air permeability testing relies on the quality of the systems sealing, engineering and manufacturing to ensure that all opening segments seal together well and fully to stop as much air travel through a system as possible.
It is important in terms of comfort to the internal spaces to ensure minimal wind/breeze intrusion and is also an important factor when it comes to environmental factors, to limit the travel of energy from the internal to the external of the system.
The European Standard regarding Air Permeability in windows and doors is EN 12207, the classification is defined by the standard testing method prEn 1026 which is conducted on the completed window or door assemblies in a factory or laboratory setting by licensed testing facilities such as the Rosenheim Institute in Germany.
The air permeability test has two components; the air permeability over the overall area of the test specimen and the air permeability related to the length of the opening joint. This is measured in units of m3/(h.m2) for the overall area and m3/(h.m) for the air permeability over the panel joint.
A test specimen of the window or door system is fixed into the testing rig and subjected to both positive and negative pressures (blowing force pressure from the front of the elevation and a vacuum sucking pressure from behind). A reference air permeability is taken at 100Pa of pressure which then defines the upper limits of its class. A specimen belongs to a specified class if the measured air permeability does not exceed the upper limit at any test pressure step in that class.
The classes for EN12207 (EN1026) range from class 0 (the lowest) to class 4 (the highest). Class 4 indicates that the window or door system has been tested under pressures up to 600 Pa and had below the class limit of air permeability through the system along the panel joint and overall system area.