Read the latest news & industry developments

Read the latest news & industry developments



Why is it so hard to guarantee an air test result?

Hugh Franklin

12th June 2024


Air Tightness Building Regulations

Why is Airtightness Hard to Predict?

Airtightness is influenced by a combination of factors, including the care and attention given during the build process, the design, detailing, and even the initial shape of the building. Consequently, predicting a building’s airtightness with precision is traditionally very challenging. This difficulty is why Building Regulations in the UK now require a ‘completion’ air test for every new build home. Even within a specific set of house types, each final air test can yield different results.

Why Do Final Airtightness Scores Vary Despite the Same Designed Score?

While you can standardise build specifications such as U-values, window choices, and wall constructions across similar house types, achieving airtightness is not straightforward. Any penetrations through walls, floors, or ceilings, such as cabling or pipework, can create leakage areas, impacting the final air test results.
Building Regulations acknowledge this variability: although an architect is required to design a continuous and robust airtightness layer, actual completion often reveals discrepancies. Even the stringent Passivhaus standard allows for some unintentional leakage, highlighting the gap between design and reality.

Why is Airtightness So Unpredictable?

Traditional airtightness solutions like tapes, sheet materials, and manually applied liquids can effectively address known leakage areas. However, these methods fall short because measuring their impact on the building’s overall airtightness is difficult—often referred to as the ‘tape and pray’ approach.

Furthermore, the only time airtightness is typically checked is with the final sign-off air test, just before handover. At this point, most surfaces and fixtures are completed, making it challenging to address hidden leakage points adequately. As a result, testers can often only treat symptoms rather than underlying issues.


How Can I Ensure My Projects Are Not Too Leaky or Too Airtight?

Scientific solutions, such as AeroBarrier, provide a more reliable approach to achieving consistent and repeatable airtightness scores. AeroBarrier’s patented system operates under positive pressure, similar to inflating a bicycle tire to find a puncture. The escaping air draws the sealant towards the leak, plugging the gap with a low-VOC mist coat. The process is monitored minute by minute to ensure consistent results—the duration of the sealing process determines the level of airtightness achieved.

Current regulations specify that the leakiest acceptable result is 8 AP50  (m3/hrm2), but stricter standards may require as low as 0.6 ACH (m3/hrm3).

Incorporating airtightness strategies from the outset of your project is crucial for ensuring compliance and avoiding costly delays. By using technologies like AeroBarrier and adhering to best practices in design and construction, you can minimise the risk of project failure and ensure on-time completions and handovers.

Discover how you can achieve & exceed Passivhaus with AeroBarrier.

Discover how you can achieve & exceed Passivhaus with AeroBarrier.