What is Air Tightness Testing?
Air Testing – also known as Air Tightness Testing, Air Permeability Testing, Air Leakage Testing, and Air Pressure Testing – measures the amount of air escaping through a building’s envelope. It helps determine energy efficiency and cost savings, for one thing. Maintaining a balance between airtightness and ventilation is another crucial element.
Do I Need an Air Tightness Test?
In the UK, all new developments generally require an Air Tightness Test as part of Building Regulations. The test is conducted before occupancy, influencing energy ratings. Commercial properties over 500 m2 and properties under 500 m2 with target emission rates typically need testing.
Why is Air Testing Important?
Air testing increases energy efficiency, ensuring buildings meet emission rate targets overall. It aligns with the government’s commitments to reduce carbon emissions. High air tightness reduces energy waste, heat loss, and draughts, benefiting the environment and occupants.
How is an Air Tightness Test Performed?
ATTMA, IATS, or UKAS-registered air testers use blower door equipment to pressurise or depressurise buildings. External openings are used to measure pressure differentials, air leakage pathways, and temperatures. The test calculates the air leakage and determines compliance with Building Regulations.
There are 3 different levels of air testing that have been established from the size and complexity of a building:
- Level 1: Single dwellings and smaller non-dwellings up to 4000 m2.
- Level 2: Larger and more complex buildings exceeding 4000 m2.
- Level 3: Large, complex, high-rise, phased, and zonal handover buildings.
Measuring the Air Permeability Index
The Air Permeability Index is determined by the volume of air passing through the fan and pressure differentials. The Maximum Air Permeability in the UK is 10 m³/hr.m². New dwellings should aim for 5 m³/hr.m² or less, but 3-5 m³/hr.m² is generally acceptable with proper ventilation.
The number of dwellings that require testing no longer depends on the method chosen for showing continuity of insulation. Instead, testing should be carried out on three units of each type or 50% of each type, whichever is less i.e.:
- 1 or 2 of a type = test 1
- 3 or 4 of a type = test 2
- 5 or more of a type = test 3
However, for sample testing to be permitted, the plots being tested need to average at least 2 m³/hr.m² or less the target of the dwelling not being tested.
Note that this is in effect a penalty, and it may result in designers demanding that all units be tested.
- You have been specifically asked to test 4 identical dwellings, with a design air permeability of 6 m³/hr.m².
- Only 2 are required to be tested and you obtain results of 4 and 5 m³/hr.m², averaging 4.5 m³/hr.m².
- Although both pass, the assessed air permeability of the other two is 6.5 m³/hr.m² (4.5 + 2 m³/hr.m²) so they both fail.
- In order to get all dwellings to pass with only one additional test, it will need to achieve a result of no more than 3 m³/hr.m² in order to push the average down below 4 m³/hr.m².
Because of this, most builders choose to test all dwellings on-site.
Future Homes Standard Update
The Part L Future Homes Standard requires air testing for all new dwellings, eliminating sample testing. Dwellings without mechanical ventilation will receive no benefit in SAP for scores below 3 m³/(h.m²).
Our testing experts have extensive experience in getting dwellings to meet the air tightness thresholds required. We work hard to go beyond mere compliance with building regulations. Our approach is to help our clients prepare and be ready to pass first time on the day of the test.
If you need support from our experienced team of ATTMA-qualified air tightness testers, get in touch.
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