How do I measure airtightness and what level of airtightness should I am to achieve?
The most commonly used unit of measurement for airtightness in Ireland and the UK is referred to as the air permeability of a building or Q50. To measure air permeability a pressure differential is induced onto a building using a large fan called a Blower Door. An airtightness measurement usually involves a combination of depressurising and pressuring a building to a pressure difference of 50 Pascal’s (50Pa) which is equivalent to a wind speed of about 20 miles per hour on every side of the building envelope at once, by no means an extreme pressure. Once the pressure differential reaches 50 Pa, air leakage may easily be located in the external envelope and an accurate measurement of the air permeability of the external envelope of the building is taken. The air permeability of a building at a pressure differential of 50Pa is referred to as the Q50 of a building and is measured in m3/hr (of airflow) per m2 (of total external envelope area). The standard upper limit level of airtightness
