Two pressure tests
A minimum of two pressure tests will be needed, and three are advisable in some cases. The first should be conducted at the end of first fix when the glazing and doors have been installed, but the airtight barrier is still open to inspection. It is recommended that the key contractor, clerk of works and site operatives are present during the pressure test in order to identify and remedy any defects in the air tightness layer.
Second pressure test
A second pressure may be carried out once the services have been installed. This is good practice particularly in timber frame construction where service run fixings and cabling may have damaged the air tight membrane.
A final test must be carried out at the completion of works. This test is needed to verify the airtightness after all of the building services have been installed and commissioned. In England this test must be carried out by a competent person registered with the British Institute of Non Destructive Testing (BINDT) and carried out in accordance with BS EN 13829 test conditions.
Once the n50 test has been passed the test certificate should be forwarded to the Passivhaus certifying body (BRE Passivhaus UK) as evidence of compliance with the air pressure testing requirement. Further information on preparing for the air pressure can be found in the Passivhaus Primer – Air pressure testing.
Excerpt from “Passivhaus primer: Contractor’s guide. So you’ve been asked to build a Passivhaus?” by BRE.