Air Tightness Testing

Air tightness testing is a mandatory requirement under Building Regulations Part L for most new build residential and non-domestic buildings in England and Wales. The test measures how much air leaks from a building and confirms whether it meets the required energy efficiency standards.

At [Your Company Name], we provide reliable, fully compliant air tightness testing services for domestic and commercial projects. Our tests are carried out by qualified technicians using calibrated equipment, with clear reports accepted by all local authority and approved Building Control bodies.

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What Is Air Tightness Testing?

Air tightness testing (also known as air permeability testing or blower door testing) measures how much uncontrolled air leakage occurs through a building’s fabric.
During the test, a high-powered fan is temporarily installed in an external doorway. The fan pressurises and depressurises the building, allowing us to measure how much air escapes through gaps, cracks, and unintended openings in the building envelope.
The result is expressed as:

· Air permeability (m³/h·m² @ 50 Pa)

This figure is used within:

SBEM calculations (non-domestic)
BREL reports
Part L compliance submissions

Why Is Air Tightness Testing Important?

Air leakage has a significant impact on:

Energy efficiency
Heating demand
Carbon emissions
Occupant comfort

Poor air tightness can lead to:

Higher energy bills
Difficulty passing Part L
Delays to Building Control sign-off

Air tightness testing ensures that the building performs as designed and that energy efficiency targets set at design stage are actually achieved on site.

When Is Air Tightness Testing Required?

Air tightness testing is required for:

New Build Dwellings

Most new residential buildings must be air tested unless a valid exemption applies.

New Non-Domestic Buildings

Commercial buildings above certain size thresholds require testing in line with Part L.

Large Developments

For multi-plot housing developments, a percentage of plots must be tested depending on the chosen compliance route.

Building Control Completion

Without a compliant air tightness test result, Building Control will not issue a completion certificate.

Air Tightness Testing & Part L Compliance

Under Part L 2021, air tightness performance plays a critical role in meeting:

DER vs TER targets
Fabric Energy Efficiency requirements
Overall carbon reduction targets

The air permeability value achieved on site is fed directly into:

SAP calculations for dwellings
SBEM calculations for non-domestic buildings

A worse-than-expected result can cause a previously compliant design to fail at as-built stage, making early planning and good site practices essential.

Domestic Air Tightness Testing

For residential properties, air tightness testing applies to:

New build houses
Flats and apartments
Conversions and change-of-use projects

What We Test:

The entire dwelling envelope
Including walls, floors, roofs, windows, and service penetrations

Typical Target Values:

Building Regulations maximum: 10 m³/h·m² @ 50 Pa
Most modern designs aim for ≤ 5 m³/h·m²
High-performance homes may target ≤ 3 m³/h·m² or lower

We work closely with your SAP assessor to ensure the test result aligns with your compliance strategy.

Non-Domestic Air Tightness Testing

Non-domestic buildings are also subject to air permeability requirements under Part L.
Typical projects include:

Offices
Retail units
Industrial and warehouse buildings
Mixed-use developments

Testing is carried out in accordance with:

ATTMA standards
Approved Document L

Our reports are fully compatible with SBEM and BREL submissions.

Design Stage Advice & Pre-Test Support

Passing an air tightness test starts long before the fan is switched on.
We provide pre-test guidance to help you avoid common causes of failure, including:

Poor sealing around windows and doors
Unsealed service penetrations
Inadequate sealing at junctions
Loft hatches and access panels

For developers and contractors, this proactive approach:

Reduces the risk of failed tests
Saves time and retest costs
Protects your build programme

On-Site Air Tightness Testing Process

Our testing process is straightforward and efficient:

Site Preparation

We confirm the building is ready for testing and that:

The envelope is complete
Windows and doors are installed
Temporary seals are in place where required

Blower Door Test

We carry out pressurisation and depressurisation tests using calibrated equipment.

Data Collection

Airflow rates are measured and recorded in line with ATTMA methodology.

Test Report

A full air tightness test certificate is issued, ready for:

SAP or SBEM input
BREL report submission
Building Control approval

Failed Air Tightness Tests

If a building fails to achieve the required air permeability:

We explain exactly why
Identify the most likely leakage points
Provide practical recommendations for improvement

Once remedial works are completed, we can carry out a re-test promptly to keep your project moving.

Air Tightness Testing for Developers & Contractors

We regularly support:

Property developers
Main contractors
House builders
Design & build teams

For larger developments, we offer:

Flexible scheduling
Multiple plot testing
Consistent reporting
Coordination with SAP, SBEM, and BREL services

This joined-up approach reduces risk and improves compliance outcomes.

What We Need Before Testing

To carry out air tightness testing, we require:

Site access
Confirmation the building is test-ready
Plot or unit details
Site contact information

We’ll advise if any preparation is needed before attending site.

Why Choose Us for Air Tightness Testing?

ATTMA-compliant testing

Calibrated, approved equipment

Qualified and experienced testers

Fast turnaround on reports

Accepted by all Building Control bodies

Integrated with SAP, SBEM, and BREL services

Our focus is on passing first time wherever possible.

Air Tightness Testing & Energy Performance

Air tightness test results directly influence:

SAP calculations
SBEM results
EPC ratings
Overall energy efficiency

A good result can:

Reduce reliance on costly renewables
Improve EPC ratings
Support long-term energy savings

We help ensure your air tightness performance works with your compliance strategy — not against it.

Areas We Cover

We provide air tightness testing across England and Wales, working on:

Single dwellings
Multi-plot developments
Commercial and industrial projects

Our service is flexible, responsive, and nationwide.

Get a Quote for Air Tightness Testing

If you need air tightness testing for a domestic or non-domestic project, get in touch today.

Call us to book a test

Email your project details for a fast quote

Building Control–ready certification

Let us handle your air tightness testing — so your project stays compliant and on track.

Professional Air Tightness Testing for Building Regulations Compliance