Residential Air Tightness Testing – Your Questions Answered
Ensuring your property meets air tightness standards is a key requirement under Building Regulations Part L. Whether you’re building a new home, renovating an existing one, or simply looking to improve energy efficiency, air tightness testing is essential. It helps reduce energy waste, lower bills, and minimize environmental impact.
Below, we answer the most common questions about residential air tightness testing, so you’re fully prepared.
What is residential air tightness testing?
Residential air tightness testing measures how much air escapes through gaps in a building’s fabric. The goal is to reduce energy loss, prevent drafts, and ensure efficient heating or cooling. A more airtight dwelling results in lower energy costs and improved comfort.
What are the UK requirements for air tightness testing?
All new homes and flats must undergo air tightness testing as specified in Part L1A of the Building Regulations and ATTMA TS1 standards.
- Permissible air leakage rates typically range between 3 and 8 m³/h.m² (cubic meters per hour per square meter) depending on the property size and type.
What about air tightness for homes with MVHR systems?
For homes using Mechanical Ventilation with Heat Recovery (MVHR), achieving a low air tightness score (below 3 m³/h.m²) is critical.
If the air leakage exceeds 3 m³/h.m², it can negatively impact your Energy Performance Certificate (EPC) score, potentially offsetting the benefits of an MVHR system compared to simpler ventilation methods like extractor fans and trickle vents.
How is an air tightness test performed?
- A blower door fan system is installed on an external door or window.
- The fan creates a pressure difference between the interior and exterior.
- Airflow is measured across 10 pressure readings (from 25Pa to 70Pa).
- The result is expressed as m³/h.m² (air leakage rate).
What are the benefits of an airtight dwelling?
- Lower energy bills due to reduced heat loss.
- Improved thermal comfort by eliminating drafts.
- Reduced carbon emissions, which is better for the environment.
- Better indoor air quality, enhancing occupant health.
Where are the common sources of air leakage?
Air leakage often occurs around:
- Wall/floor junctions and roof eaves.
- Windows and doors (especially double doors).
- Pipe and cable penetrations.
- Extractor fans, cooker hoods, and ceiling lights.
- Sockets, letterboxes, and joist ends.
How can I reduce air leakage?
Minimize air leakage through smart design and careful construction:
- Use vapour barriers and airtight membranes.
- Seal gaps with tapes, foams, or caulks.
- Install double/triple-glazed windows.
- Apply weather stripping or draught excluders.
- Follow an air leakage checklist during construction or refurbishment.
What is an air tightness champion?
An air tightness champion ensures the integrity of the airtight barrier during construction. Often the site manager or foreman, they oversee the build phase, report issues, and ensure high standards are maintained — a role critical for projects aiming for Passivhaus standards.
How does air tightness testing help meet Passivhaus standards?
Passivhaus buildings require an extremely low air leakage rate of 0.6 ACH (air changes per hour) at 50 Pa, roughly equivalent to 0.5 m³/hr/m².
Air tightness testing verifies compliance with these standards and, when combined with smoke or thermal surveys, helps identify problem areas for improvement.
Are there risks to overly airtight homes?
While airtight homes are energy-efficient, poor ventilation can cause:
- Insufficient fresh air.
- Excess moisture and mould growth.
- Poor indoor air quality, leading to health risks.
To mitigate these risks, install balanced ventilation systems like MVHR to ensure adequate airflow and moisture control.
What if my building fails the air tightness test?
If a dwelling fails:
- We conduct blower door smoke and/or thermal imaging surveys to pinpoint air leakage paths.
- Repairs can often be made immediately to achieve a pass.
- For significant leakage, we provide a detailed air leakage report to guide remedial work.
How often should air tightness testing be carried out?
Air tightness tests should be performed at the pre-completion stage, around 2 weeks before handover. The building envelope must be complete, with final touches underway. Use our air testing checklist to ensure you’re ready.
Is air tightness testing useful for refurbishments?
Yes. Testing existing dwellings before renovation identifies air leakage rates and defects. For systems like MVHR or air source heat pumps to function efficiently, dwellings must achieve an air tightness of 3 to 5 m³/h.m². Older homes often exceed 15 m³/h.m², meaning targeted sealing work may be necessary.
We can perform smoke and thermal imaging surveys to guide improvements.
How can I find a professional air tightness tester?
Look for companies accredited by:
- UKAS (United Kingdom Accreditation Service)
- ATTMA (Air Tightness Testing & Measurement Association)
Accredited testers comply with standards like ATTMA TS1/TS2 and CIBSE TM23 (2022). APT Sound Testing is both UKAS and ATTMA accredited, ensuring professional service.
Why choose APT Sound Testing?
- Fully accredited for air tightness testing on all dwelling sizes, including large projects over 1000m².
- Expertise on prestigious projects such as The Imperial War Museum and Battersea Power Station.
- Unique combined smoke and thermal imaging surveys for accurate air leakage detection.
If you need air tightness testing or air leakage surveys, contact APT Sound Testing today.
- Phone: 07775 623 464
- Website: https://aptsoundtesting.co.uk
