Air Tightness Testing

Air tightness testing, also known as air permeability testing or air leakage testing, measures the amount of uncontrolled air escaping from or entering a building. It’s crucial for identifying leaks in the building fabric, which can lead to significant heat loss and increased energy consumption.

Effective air tightness reduces heat loss, lowers energy bills, improves thermal comfort, and enhances indoor air quality. It is also a mandatory requirement under Building Regulations for many new constructions and significant renovations.

A good air tightness score indicates a well-sealed building, leading to:

– Reduced energy consumption for heating and cooling.
– Lower carbon emissions.
– Improved thermal comfort (fewer drafts).
– Better indoor air quality (when combined with controlled ventilation).
– Compliance with Building Regulations.

Our experienced engineers provide valuable on-site advice during the test. If a property is unlikely to pass, we can help identify leakage points and advise on immediate fixes to improve your chances of passing on the first visit. We also offer preliminary tests for new builds to identify issues early in the construction process.

We pride ourselves on speed and efficiency. 95% of our tests are conducted within two weeks of booking, and most certificates are provided within 24 hours of the test completion.

This is the most common and standard method. It involves installing a powerful fan into an exterior doorway to create a significant pressure difference (typically around 50 Pascals) between the inside and outside of the building. By measuring the airflow needed to maintain this pressure, the building’s overall air leakage rate is calculated. This method is excellent for verifying construction quality and for detailed diagnostics to pinpoint specific leak locations, making it highly effective for new builds and retrofit evaluations.

A alternative method that involves releasing a quick, precise burst of air into the building and analysing the pressure decay over a short period. It operates at a much lower pressure range than blower door (around 4 Pascals), making it particularly suitable for occupied buildings or for quick, preliminary assessments, especially in smaller, simpler layouts. While faster and less intrusive, it has a more limited ability to directly identify specific leak locations compared to blower door testing.

Often used in conjunction with a blower door test, this involves introducing harmless smoke into the building (or blowing it from outside) while the building is pressurised or depressurised. The smoke then visually reveals the precise location of air leaks and gaps, allowing for targeted sealing and repairs.

All new dwellings need an air tightness test in order to calculate the dwelling emission rate (DER) as part of the mandatory SAP calculation process. This is normally done just before practical completion, with the result determining, in large part, what the final EPC rating of the building will be.

We also offer preliminary air tightness tests. Ensuring that all plots pass their final air tests on the first attempt can seem like a challenge, but it doesn’t have to be. An early test can provide valuable data on potential leakage points, enabling site-wide improvements before final testing ans so avoiding costly retests, schedule delays, and construction friction.

All new commercial buildings have needed an air leakage test in order to comply with building regulations since 2003. Beyond compliance, however, conducting air test throughout the construction process will help keep air leakage through the building fabric to a minimum. 

Our engineers are experienced in testing a wide variety of commercial properties (office blocks, accommodation blocks, schools, hospitals, industrial units, laboratories, etc.) and have a great understanding of finding any air leakage or heat loss areas of the building.

Also referred to as Passive House air tightness testing, or low energy air testing, these tests are designed to ensure the stringent standards set by the Passivhaus Institute are met. The testing process is more complex, with multiple stages, and each project requires at least three tests along the design and build phases.

Some public funded retrofit projects following the PAS 2035 framework require an air tightness test. Most retrofit assessors in the UK are not qualified air testers, meaning that air tightness testing has to be done by an additional supplier. We cross-train our staff so that they can undertake both assessments and air tests in a single visit, creating less disturbance for residents and reducing the overall cost of the project.

Conducted for any existing building where owners or occupants are looking to improve energy efficiency, address comfort issues (like drafts), reduce energy bills, or prepare for future upgrades, even if not part of a formal regulated retrofit scheme.

While not a direct MEES requirement, improving air tightness is a highly effective way to enhance a property’s EPC rating, helping landlords meet Minimum Energy Efficiency Standards (MEES) for existing rented buildings.

For commercial properties, even without physical changes, incorporating an actual air tightness score (rather than relying on default values) can significantly improve a commercial property’s EPC rating.

Undertaken in line with technical standard BTS 03 to validate air permeability in critical isolation facilities (e.g., healthcare, laboratories, data centres). Achieving low air tightness is vital for controlling airborne infections and maintaining design pressurisation levels.