Serving Luton and surrounding areas
Building Regulations Part L
Air Tightness Testing in Luton and Surrounding Areas
ATTMA accredited air permeability testing to demonstrate Part L compliance. Our certified technicians deliver fast, reliable results with detailed reporting for building control sign-off
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Calibrated equipment
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Luton & 50-mile area
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Accreditations
- Elmhurst
- ATTMA
What Is Air Tightness Testing?
Air tightness testing, also known as air permeability testing or blower door testing, is a method of measuring how much air leaks through the fabric of a building. The test is conducted by temporarily sealing a building, installing a calibrated fan in an external doorway, and pressurising or depressurising the building to measure the rate of air leakage.
The result is expressed as cubic metres of air per hour per square metre of building envelope area at a pressure differential of 50 Pascals (m³/h.m² @50Pa). This figure is compared against the design air permeability specified in the SAP or SBEM calculation for the building.
Air tightness testing is a mandatory requirement under Building Regulations Approved Document Part L (Conservation of Fuel and Power). It applies to all new dwellings and most new non-domestic buildings. The test demonstrates that the building has been constructed to a sufficient standard to minimise uncontrolled air leakage, which contributes to energy efficiency and thermal comfort.
Who Needs an Air Tightness Test?
Under Part L of the Building Regulations, an air tightness test is required for:
All new-build dwellings
New non-domestic buildings with a floor area greater than 500m²
Extensions and conversions (where required by building control)
Buildings undergoing a material change of use
Social housing and affordable housing developments
When Is Air Tightness Testing Required?
Air tightness testing should be scheduled once the building envelope is substantially complete. This means all external doors, windows, and rooflights are installed, all service penetrations through the envelope are sealed, and the building is in a condition that represents its final airtight state.
It is important to test before internal decoration begins. If the building fails to meet its target air permeability, remedial work will be required, and this is much easier to carry out before plasterboard is decorated or flooring is laid.
How Does the Air Tightness Test Process Work?
Our accredited technicians follow a standardised procedure in accordance with ATTMA TSL1 (dwellings) or TSL2 (non-domestic buildings):
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1
Preparation
All external openings are closed. Internal doors are opened. Mechanical ventilation is turned off. Extract fans, flues, and other intentional openings are temporarily sealed.
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2
Equipment Setup
A calibrated blower door fan assembly is installed in an external doorway. Pressure gauges and flow measurement devices are connected.
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3
Pressurisation & Depressurisation
The building is pressurised and depressurised to 50 Pascals. Air flow rates are measured at multiple pressure increments to establish a reliable result.
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4
Leak Detection
If required, a smoke pencil or thermal imaging can be used to identify specific air leakage paths for remediation.
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5
Reporting
Results are calculated and a detailed report is produced, including the measured air permeability, pass/fail status, and any observations. Reports are typically delivered within 24–48 hours.
How Does the Air Tightness Test Process Work?
What is air tightness testing?
Air tightness testing (also known as air permeability testing or blower door testing) measures the rate at which air leaks through the building envelope. It is a mandatory requirement under Building Regulations Approved Document Part L for new builds and certain refurbishments.
Who needs an air tightness test?
All new dwellings and non-domestic buildings require an air tightness test to demonstrate Part L compliance. Conversions, extensions, and refurbishments may also require testing depending on the scope of work and local building control requirements.
When should air tightness testing be carried out?
Testing should be carried out once the building envelope is complete - meaning all doors, windows, and service penetrations are sealed. It must be done before internal decoration to allow for any remedial work if needed.
How long does an air tightness test take?
A standard dwelling test typically takes 1–2 hours. Larger or more complex buildings may take longer. We can test multiple units on the same day to keep your programme on track.
What happens if my building fails the air tightness test?
If a building fails to meet the design air permeability, our technicians will conduct a smoke test to identify leak paths. We provide guidance on remedial measures and can return for a re-test once issues are addressed.
How should I prepare for an air tightness test?
Ensure all external doors and windows are fitted and closed, all service penetrations are sealed, mechanical ventilation is turned off, and any extract fans or flues can be temporarily sealed. We provide a full preparation checklist when you book.
What are ATTMA accredited testers?
ATTMA (Air Tightness Testing & Measurement Association) accredited testers have demonstrated competence in air pressure testing. Using ATTMA members ensures tests are conducted to recognised standards and results are accepted by building control.
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