To determine how permeable a building’s fabric is to uncontrolled air, an air tightness test or blow door test is used. The rate of permeability is calculated by positioning a sizable fan at the front door of the house and producing a pressure difference of at least 50 Pascals.

A house will cost less to operate if its air permeability rate is lower, and it will cost more to operate if it is too high. If a new construction fails the air pressure test due to excessive draught, the house will not be in compliance with building rules. The air tightness tester will be able to determine why a property fails.

We strongly advise passing a preliminary test. The builder uses the provisional test to help identify infiltration points. The provisional test is performed after the house has been airtighted, meaning that the windows have been sealed with airtight tapes, the walls have been sealed with sand and cement or airtight membranes, and the attic and roof have been sealed with airtight membranes.

When the house is completely finished, the last test is run.

According to technical guidance document part L 2019, all new homes must pass an air tightness test and reach an air tightness target of less than 5 ach/hr.