Construction
Air-tightness of buildings
The Earth’s limited energy reserves and the increasing burden on the environment caused by fossil fuels is forcing people to save energy.
Among other things, the introduction of the Energy Saving Ordinance EnEV in 2002 was designed to restrict the uncontrolled air exchange between heated internal air and cold external air to save on energy loss.
The prerequisite for this is the careful design of the air-tight building parts, such as windows and doors, wind-proofing and vapour barrier films in the roof and plaster render on external walls.
An approved process for testing a building’s air-tightness is the blower door measurement method. 
The measurement method
In the blower door measurement method, the testing device is mounted air-tight in the window or door opening and generates overpressure or underpressure.
The measured pressure difference between the external and internal air allows the calculation of the outgoing or incoming air and, potentially, the localisation of existing leaks in the air-tight building.
The maximum permissible air-exchange rate as per the Energy Saving Ordinance (EnEV 2002) for buildings with natural ventilation (window ventilation) may not exceed 3 times the interior volume (n50 3 [h-1]).
For buildings with mechanical ventilation systems, the air volume exchange may not exceed 1.5 times n50 1.5 [h-1] per hour.
Localising leaks
Adherence to the maximum permissible air-exchange rate alone is not enough evidence that all air-tight building components are defect-free. For this reason, each measurement should be accompanied by an assessment of the individual leaks.
If there are only a few, albeit large, leaks in the building, this poses the risk of considerable condensation within a small area. This can also occur even if the EnEV maximum permissible air-exchange rate requirements are met for the building.
Further information about buildings you can find here:
http://www.tuev-nord.de/en/BUILDINGS_3400.htm
Further information about air / ambient air you can find here:
http://www.tuev-nord.de/en/environment/AIR_3418.htm
