Air permeability
Air permeability refers to the air exchange between the room and the outside. Windows and doors are never absolutely airtight. For optimal air quality in the rooms this is also not desirable. Excessive air exchange likewise reduces quality of life and, moreover, causes high heating costs.
Air permeability (formerly referred to as the a-value) is currently expressed by the Q-value and classified according to the standard DIN EN 12207. In the case of complete components (e.g. windows or doors), an area-related value can be given - the ratio of the air volume in m3 to the area per hour (m3/m2 times h). For the joints, a length-related value can be given - the ratio of the air volume to the length of the joint per hour (m3/m times h). The reference point is an air pressure of 100 Pa.
| Air-tightness classes: | relative to total area | relative to joint length |
|---|---|---|
| Class 0 | Not tested | Not tested |
| Class 1 | 50 m3/m2 h | 12.50 m3/m h |
| Class 2 | 27 m3/m2 h | 6.75 m3/m h |
| Class 3 | 9 m3/m2 h | 2.25 m3/m h |
| Class 4 | 3 m3/m2 h | 0.75 m3/m h |
