An airtight building envelope prevents condensation or structural damage and heat loss through uncontrolled ventilation. In addition, compliance with the air tightness limit values is a requirement for cost savings. This can be determined by the Blower Door measurement (air tightness measurement).
The Blower Door measurement is a pressure difference measurement in which the influence of the wind at wind force 5 on a building is simulated. This corresponds approximately to the conditions on a stormy autumn day. The air exchange rate is determined and leaks in the building envelope are documented.
The measuring methods are described in EN 13829 and EN ISO 9972 and differ in the building preparation:
The building envelope is tested to prove that it meets the country-specific requirements. All openings to the outside are sealed (e.g. cat flaps, window rebate ventilators, exhaust air openings, fume extraction system,... etc.).
For example in order to prove the requirements according to the German GEG (Building-Energy-Law), the building is checked in its state of use. Here, openings that can be closed are closed, but not additionally sealed. All other openings in the building envelope remain unchanged.