If you’ve heard the term “air testing” or “air tightness test” and aren’t sure what it actually involves – or whether your project needs one – this guide covers both.
In this blog you’ll learn:
- What air testing is and why it’s important
- Whether you need an air tightness test for your property
- How the air test is performed
- What the latest regulations on air tightness testing are
What Is Air Tightness Testing?
“What is an air tightness test all about and do I really need one?” is one of the most common questions we get asked. Air Tightness Testing – also known as Air Testing, Air Permeability Testing, Air Leakage Testing, and Air Pressure Testing – measures the amount of air escaping through cracks and gaps in the building envelope. A more airtight building translates to better energy efficiency, lower heating and cooling costs, and a more comfortable living environment. Maintaining a balance between airtightness and ventilation is another crucial element.
In short, air tightness testing measures how much air leaks out of a building – a check-up on how energy efficient it is.
Do I Need a Building Air Tightness Test?
The need for an air tightness test depends on a few different factors:
- Location: in the UK, all new developments generally require a test as part of Building Regulations. The test is conducted before occupancy, influencing energy ratings.
- Building size and type: commercial properties over 500 m² and some smaller buildings with specific target emissions typically need testing.
- Future Homes Standard: the Part L Future Homes Standard mandates air tightness testing for all new dwellings, eliminating sample testing. Dwellings without mechanical ventilation receive no SAP benefit for scores below 3 m³/(h.m²).
- Existing buildings: air tightness testing isn’t only a new-build requirement. On retrofit projects, a test can establish a baseline before works begin and be repeated afterwards to demonstrate the improvement – figures which can also feed into an updated EPC.
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 reducing carbon emissions. High air tightness reduces energy waste, heat loss, and draughts, benefiting both occupants and the environment.
How Is A Building Air Tightness Test Performed?
Qualified air testers (ATTMA, IATS, or UKAS-registered) use blower door testing equipment to pressurise or depressurise a building. 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.
How Much Does An Air Tightness Test Cost?
There’s no single price for an air tightness test – the cost depends on the size and complexity of the building, the testing level required, how many visits are needed (an in-construction test followed by a final test, for example) and whether the property is a straightforward single dwelling or a larger, more complex development.
For developments with multiple plots tested in a single visit, we charge full price for the first plot and a significantly reduced rate for each subsequent plot.
The most reliable way to get an accurate figure is to get a quote based on your specific project.
What’s next?
Deciding whether you need an air tightness test usually comes down to what you’re building, where and to what standard – but if you’re at all unsure, it’s worth checking before it becomes a compliance issue late in the project.
If you’re planning a test and want to know what to expect on the day, our team is happy to talk it through.
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