AirTightness
What is airtightness?
The airtightness of a building is how much air leakage a building has through its envelope. The more airtight a building is, the less air leaks it has.
Airtightness is usually measures in air changes per hour or air permeability rate (m3/hr/m2). The higher these figures, the more warm air is escaping and therefore, the more energy is being used.
Why is airtightness important?
Airtightness now forms part of the building regulations under technical guidance document L. Section 1.3.4.4 states that air pressure testing should be carried
out on all dwellings on new development sites.
In addition to airtightness being a regulation it is also important as the more airtight your home is the cheaper your energy bills will be and the more environmentally friendly your home is.
How is airtightness measured?
Airtightness is measured by carrying out an air permeability test in the form of a blower door test. The procedure for testing is specified in I.S.EN ISO 9972:2015.
The regulations stipulate than a minimum air permeability rate of 5m3/hr/m2 should be met.
what is a blower door test?
During the test, windows, flues, chimneys and vents are sealed up. A fan is placed in a door and air is sucked out of or blown into the building creating a pressure difference between the inside and outside.
The air flow is recorded at a pressure difference of 50pa and measures the leakage per square metre of the external building envelope (e.g. permeability through the walls/floors/ roof) .
what do my results mean?
We will provide you with a report after the test in both paper and digital form. These results will also be clearly explained to you by our tester.
In order to comply with part L of the building regulations you need to achieve a result of 5m3/hr/m2. Anything less than 3m3/hr/m2 will require mechanical ventilation. To qualify as a passive house a result of 0.6m3/hr/m2 is required.