Air Tightness Testing: What You Need to Know

A well-built property should be comfortable, energy efficient and able to keep unwanted air leakage under control. This is where air tightness testing plays an important role.

At APT Sound Testing, we provide professional air tightness testing across the UK, working on everything from individual homes and housing developments to large commercial buildings. We are one of the few UKAS-accredited companies able to carry out both air and sound testing to the relevant Building Regulations and standards.

Because our engineers are qualified to carry out multiple types of testing, we can often complete air, sound and ventilation testing during the same visit. This can save our clients money, reduce disruption and make site coordination much easier. Unlike many testing companies, we also carry out our own work rather than subcontracting it.

What is air tightness testing?

Air tightness testing, sometimes referred to as an air permeability test or blower door test, measures how much uncontrolled air leakage occurs through a building’s envelope.

Every building needs some ventilation, but uncontrolled air movement through gaps, cracks and joints in the building fabric can waste energy. These unwanted gaps are commonly experienced as draughts.

During an airtightness test, specialist blower door equipment pressurises or depressurises the building. The equipment measures the airflow required to maintain a set pressure difference between the inside and outside of the building. This allows the building’s air leakage rate to be calculated.

The more airtight a building is, the less conditioned air it loses unnecessarily. This can reduce energy consumption, lower carbon emissions and reduce the demand placed on heating, cooling and mechanical ventilation systems.

Why is air tightness testing important?

Air tightness testing became a legal requirement for many new buildings in England and Wales in 2006 under Part L of the Building Regulations.

Part L covers the conservation of fuel and power and includes requirements for the energy performance and air permeability of buildings. For domestic projects, Part L1A is generally applicable to new dwellings, while Part L2A relates to new non-domestic buildings.

The required air permeability target depends on the building type and design. A common target for a standard dwelling is around 5.0 m³/hr/m² at 50 Pa, although the required figure depends on the specific project. Commercial buildings can have significantly lower target air permeability rates, often around 3.0 m³/hr/m² or below.

Meeting the required target is important for achieving Building Control approval and demonstrating that the building has been constructed in accordance with its design requirements.

Where does air leakage occur?

Air leakage can occur almost anywhere there is an unintended gap or break in the building envelope.

Common problem areas include:

• Around windows and doors
• Service penetrations
• Floor and wall junctions
• Roof and ceiling junctions
• Electrical sockets and fittings
• Pipe and cable penetrations
• Around ventilation systems
• Poorly sealed joints
• Gaps between construction materials

One challenge is that individual leaks can be difficult to see. A building may have dozens, or even hundreds, of relatively small leakage paths which collectively have a significant effect on its overall air permeability.

This is why testing during construction, rather than waiting until the very end of a project, can be so valuable.

Air leakage, condensation and moisture

Uncontrolled air movement can cause more than just wasted energy.

In winter, warm, moist indoor air can pass through gaps in the building fabric and reach colder areas within walls, floors, or roofs. Depending on the construction and conditions, this can contribute to condensation and potentially lead to mould, damp or deterioration of building materials.

During warmer or more humid periods, unwanted infiltration can also introduce humid outdoor air into a building.

A properly designed and constructed air barrier helps control where air enters and leaves the building. This makes it easier to manage energy use, indoor comfort and moisture movement.

How much heat can be lost through air leakage?

The amount of heat lost through air leakage varies considerably depending on the building, its construction and the extent of the leakage.

Poor airtightness can significantly contribute to heat loss and increase the energy required to maintain comfortable indoor temperatures. In some poorly performing buildings, uncontrolled air leakage can account for a substantial proportion of overall heat loss.

An air tightness test provides measurable information about building performance rather than relying on assumptions.

What does an air tightness test tell you?

A blower door test does more than provide a pass-or-fail result.

The test measures the amount of air moving through the building at a known pressure difference. This information helps you understand how well the building envelope is performing and, when needed, investigate individual leakage paths.

Finding air leakage paths

One of the biggest advantages of testing is that it can help identify areas where air is escaping or entering the building.

At APT Sound Testing, our engineers can use techniques such as smoke testing alongside blower door testing to help locate leakage paths.

Sometimes one or two relatively large gaps cause the problem. More often, however, a building’s overall air leakage results from numerous smaller defects spread throughout the building.

Finding these issues before completion allows contractors to seal them and improve the building’s performance before the final test.

Improving energy efficiency

Every time conditioned air escapes a building, replacement air must be heated or cooled. The greater the uncontrolled air leakage, the greater the potential energy requirement.

Air tightness information can therefore be useful when considering energy consumption, heating and cooling requirements and the overall performance of the building.

Improving occupant comfort

Draughts can noticeably affect the comfort of people using a building.

Cold air entering through unintended gaps can create uncomfortable conditions, particularly in homes, offices and other occupied spaces.

We have previously investigated buildings where occupants were experiencing significant comfort problems. In one case, testing identified an air leakage rate of approximately 25 m³/hr/m². Once the leakage paths were identified and sealed, the building achieved an air permeability below 5 m³/hr/m², significantly improving its performance.

Reducing the risk of moisture problems

Uncontrolled air movement can carry moisture through parts of the building fabric. Depending on the construction, this can contribute to condensation and other moisture-related problems.

Good air barrier design and careful construction can reduce these risks by controlling where air can move through the building envelope.

Controlling outdoor pollutants

Air leakage can also allow outdoor pollutants to enter a building through uncontrolled routes.

For properties close to busy roads, garages, commercial premises, restaurants or other potential pollution sources, this can be an important consideration. A well-designed and properly constructed air barrier helps provide greater control over where outdoor air enters the building.

When should you carry out an air tightness test?

Although the final air tightness test is normally carried out before completion, we recommend considering air permeability from the earliest stages of a project.

Consider the design of the building’s air leakage line alongside the construction details. Everyone involved in the project should understand where the air barrier is located and how it will be maintained around junctions, openings, and service penetrations.

Early testing can also be extremely useful.

If an initial test identifies problems while the construction team is still on site, leakage paths can usually be repaired more easily than after the building is complete.

Air tightness consultancy and design reviews

At APT Sound Testing, our involvement doesn’t have to start on the day of the final test.

We provide air tightness consultancy and design reviews to help clients identify potential problems before they become expensive to fix. We can work with project teams throughout the design and construction process, providing practical advice on reducing unwanted air leakage and achieving the required target.

Our experience across a wide range of residential and commercial developments means we understand the practical challenges that can affect air permeability results.

We also provide guidance to help contractors prepare for testing, including our air tightness checklist.

Combine air and sound testing to save time and money

One advantage of working with APT Sound Testing is that our engineers are UKAS accredited to carry out both air and sound testing.

This means we can often combine testing into a single planned visit.

For many projects, our clients use our three-step pre-completion testing package, reducing the need to coordinate several different testing companies.

Combining tests can provide:

• Reduced testing costs
• Fewer site visits
• Less disruption to the construction programme
• Easier site coordination
• A single point of contact for multiple testing requirements

Where required, we can also arrange out-of-hours testing, including Saturdays and Sundays. This can be particularly useful on busy commercial developments where testing during normal working hours could disrupt other trades or occupants.

Why choose APT Sound Testing?

We have extensive experience carrying out airtightness testing on developments throughout London and across the UK.

Our team understands building regulations requirements and the practical challenges of achieving an airtight building. Rather than arriving only to carry out a final test, we can work with your project team throughout the design and construction stages to help identify potential issues before they become problems.

Whether you need a final compliance test, early-stage testing, leakage investigation or advice on your air barrier design, our experienced engineers can help.

If you are planning a new residential or commercial development and need advice on airtightness testing, get in touch with the APT Sound Testing team. We can discuss your project, explain what testing is required and help you plan for a successful result.

Need help preparing for your air tightness test? Contact our team by calling 01525 303905 or by using our online contact form.

Specialist Air Tightness Testing for COLO Data Centres & HAC Corridors

APT provides specialist air tightness testing for data centres, including COLO suites, data halls, containment pods and Hot Aisle Containment (HAC) corridors.

Our testing helps data centre operators verify containment performance, minimise unwanted airflow, maintain stable rack inlet temperatures and optimise cooling efficiency. As a UKAS-accredited air testing laboratory, APT provides accurate testing, detailed analysis and clear reporting to support commissioning, compliance and ongoing operational performance.

Our specialist testing identifies leakage paths, measures containment performance and highlights areas where improvements may be required to achieve the intended airflow separation within mission-critical environments.

Why Air Leakage Testing Matters in Modern Data Centres

Effective airflow containment is essential to maintain efficient, reliable data centre cooling. Uncontrolled air leakage can allow conditioned and return air to mix, reducing cooling effectiveness and creating unnecessary load on CRAH and CRAC systems.

Air tightness testing can help operators achieve:

• Reduced cooling energy consumption
• More stable rack inlet temperatures
• Lower bypass airflow
• Improved CRAH/CRAC efficiency
• Better airflow separation
• Improved cooling performance for high-density IT environments

Poorly sealed COLO pods, containment systems or HAC corridors can contribute to thermal instability, hot spots and increased cooling demand.

APT’s specialist testing provides measurable evidence of containment performance and helps identify areas requiring remedial work.

What We Air Test in Data Centres

APT can test a range of containment and airflow-controlled areas, including:

• COLO containment zones
• HAC corridors
• Hot aisle containment systems
• Pod-based containment systems
• Return-air plenums
• Data hall containment enclosures

Our testing can assess both operational leakage performance and construction air tightness, giving operators and project teams a comprehensive understanding of how effectively the containment system is performing.

Key Airtightness & Leakage Measurements

3% Leakage Criterion – Performance Testing

APT can assess HAC and COLO containment leakage against the specified project performance criterion, including a 3% leakage target based on the design IT airflow, where tthe projecthas bdopted fthis criterion

This provides a practical measure of how effectively the containment system is separating supply and return airflow under controlled test conditions.

Always confirm the applicable leakage criterion against the project’s design specification, commissioning requirements, and relevant standards.

ATTMA Air Tightness Testing – Construction Quality

APT can also measure air leakage relative to the enclosure’s surface area. This assesses the physical airtightness and construction quality of the containment system.

Testing can help identify defects such as:

• Poorly sealed doors
• Gaps around containment panels
• Inadequately sealed joints
• Cable and service penetration leakage
• Floor and ceiling interface gaps
• Construction defects within the enclosure

Using both performance-based leakage measurements and air permeability testing gives project teams a more complete picture of containment quality.

High-Pressure Integrity Testing for COLO & HAC Enclosures

In addition to operational air leakage testing, APT can undertake high-pressure integrity testing of COLO pods and HAC corridors.

A higher-pressure test, typically around 75 Pa where specified, can expose weaknesses that may not appear during lower-pressure operational testing.

Potential issues can include:

• Panel deflection
• Door movement or bowing
• Seal failure
• Roof-panel movement
• Plenum interaction
• Weaknesses around interfaces and penetrations

High-pressure testing provides additional information about the enclosure’s behaviour and integrity under increased pressure conditions. This can be particularly useful when assessing containment systems during commissioning or investigating performance concerns.

Blower Door Smoke Air Leakage Surveys

APT also provides specialist blower door smoke leakage surveys for COLO suites and HAC corridors.

This diagnostic approach combines controlled pressure testing with smoke tracing to identify the location and direction of unwanted air movement visually.

Smoke surveys can reveal leakage paths that may be difficult to locate through airflow measurements alone, including:

• Leakage around containment doors and seals
• Gaps between panels and roof sections
• Cable tray and service penetrations
• Leakage at floor interfaces
• Plenum bypass routes
• Construction defects behind or around IT equipment

By pressurising the containment area and introducing controlled smoke, our engineers can trace air movement and identify specific leakage locations.

Photographic evidence can then help contractors undertake targeted remedial sealing.

This makes blower door smoke surveys particularly useful during:

• Data centre commissioning
• Pre-go-live inspections
• Defect investigations
• Remedial works
• Post-remediation validation

Our Data Centre Air Tightness Testing Process

APT’s testing process can include:

1. Initial assessment of the containment area and test requirements.
2. Test preparation, including identifying and temporarily sealing relevant openings where required.
3. Blower door installation and controlled pressurisation of the test enclosure.
4. ATTMA flow-curve analysis and leakage measurement.
5. Operational pressure testing, including testing at 7.5 Pa where specified.
6. Higher-pressure integrity testing, where required by the project.
7. Smoke-tracing diagnostics to identify individual leakage paths.
8. Leakage identification and photographic documentation.
9. Clear reporting against the agreed project criteria.
10. Practical recommendations for remedial sealing and retesting.

This gives project teams clear, actionable information on the airtightness and containment performance of their data centre environment.

Benefits of Air Testing COLOs & HAC Corridors

Specialist air tightness testing can help data centre operators and project teams achieve:

• Reduced cooling energy consumption
• Lower unwanted or bypass airflow
• Improved CRAH/CRAC performance
• More consistent rack inlet temperatures
• Better airflow separation
• Improved cooling performance for high-density loads
• Greater confidence during commissioning
• Identification of construction defects before handover
• Verification of remedial works
• Improved long-term containment performance

For mission-critical facilities, early leak detection can prevent avoidable cooling inefficiencies and increase confidence that the installed containment system is performing as intended.

Why Choose APT for Data Centre Air Testing?

APT specialises in air tightness testing for data centres, combining air testing expertise with an understanding of containment systems and the airflow requirements of mission-critical environments.

We provide:

• Accurate leakage measurements
• Detailed and easy-to-understand reports
• Specialist diagnostic testing
• Smoke leakage surveys
• High-pressure integrity testing
• Practical, contractor-friendly recommendations
• Post-remediation verification
• UK-wide testing coverage

Our services support data centre operators, COLO providers, M&E consultants, commissioning teams, main contractors and mission-critical facility managers.

APT provides testing across the UK, including major data centre locations such as London, Manchester, Poole, Dorset and other UK data centre hubs.

Get a Quote for COLO & HAC Air Tightness Testing

APT Sound Testing provides specialist airtightness testing for COLO suites, HAC corridors, and data centre containment systems across the UK.

Whether you require testing during construction, commissioning, pre-go-live checks, or after remedial works, our team can provide accurate measurements, diagnostic investigation, and clear reporting.

For more information or to discuss your data centre testing requirements:

Email: info@airpressuretesting.net
Telephone: 01525 303905

Contact APT today to discuss your COLO or HAC air tightness testing requirements and arrange a quotation.

APT Sound Testing – Air Tightness Testing Service

APT Sound Testing provides air tightness testing across London and the United Kingdom. We undertake air testing on all types of projects from single dwelling to the largest commercial buildings and data centres. We are one of the few companies that are UKAS accredited to undertake both Air & Sound testing in compliance to Building Regulations and Standards. This means we can undertake Air, Sound and Vent Testing Packages during the same visit which provides our clients with cost savings and improved on site co-ordination. Unlike many companies we do not subcontract our works.

Also known as blower door testing, air tightness testing, is the process of measuring the amount of air leakage from a building through the building envelope. To try and help our clients better understand and prepare for their air tightness testing, we have tried to explain and answer our customer’s most common questions. For more information on our air tightness testing services you can also visit our Services Page.

What is Air Tightness Testing for Building Regulations?
Air testing is mandatory in the United Kingdom and is governed by Part L of the Building Regulations, this split into two parts; for domestic properties Part L1A should be used and for commercial properties Part L2A should be referenced.

Building Regulations Part L states air tightness testing should be carried to check the air leakage that occurs through a buildings envelope. The air leakage test checks the amount of air that escapes through gaps or air leakage paths through the building fabric. If the building is more air tight, less energy will be being needlessly lost, thus lowering the carbon emissions of the building. Air testing also shows how efficient a building is at retaining conditioned air which will also put less straight on your mechanical and ventilation system. Failing to maintain adequate air tightness can lead to up to 50% of heat loss from within a building to the outside atmosphere.

What air leakage target do I need to achieve?
Most new dwellings and commercial buildings need to achieve an air leakage of 3m3/hr/m2 to 5m3/hm2, this rate would usually be acceptable by building control and your SAP assessor as an acceptable result, although you need to check each your designed SAP assessment as there may be items within your buildings design that that may affect this figure.

How long does the air test take?
Most air tightness tests can be completed in 1-2 hours if they pass straight away; however, tests can take much longer if they initially fail. It usually speeds up the process if customs prepare their buildings in-line with our air tightness checklist as its means we can start the testing as soon as we arrive on site instead of waiting for the client to tape up areas, or make upgrades to the building envelope.

We also offer a smoke testing service to locate the air leakage paths within a building envelope which can also take extra time; however this often allows our clients to seal and pass their building at the first attempt even if their building initially fails the air test.

How do you undertake an air tightness test?
The air tightness test is undertaken in-line with Building Regulations Part L1 & L2 and ATTMA TS1 & TS2. Basically we measure the pressure differential across the envelope of the building by means of the temporarily installation of a large fan inside a door panel. Thereafter, a range of static pressures and environmental readings are taken.

The fan is switched on and the air pressure in the property is gradually increased or decreased and the differential pressure is recorded at each step, usually from 25 Pa to 70 Pa. The total air flow required to achieve a pressure differential of 50 Pa is calculated and divided by the total building envelope area to provide the leakage rate in m3/h.m2@50Pa.

How do I prepare my building for the air test?
The more complete you’re building the more chance you have of passing the air tightness test at the first attempt. We send our and air test checklist with every quotation to help our client prepare for the testing. It is our aim to help clients pass their air test at the first attempt.

Basically you prepare the building in-line with our checklists and the items below, you will generally have a much better chance of passing the testing at the first attempt.

1. The building envelope should be fully complete; this includes walls, floors and ceilings.
2. All doors and windows must be fully fitted and able to shut tightly against their seals.
3. All electric fittings must be installed and functional.
4. All mechanical fittings must be installed and functional.
5. Gaps within walls and floors must be sealed.
6. All service penetrations must be fully sealed through the building envelope.
7. Bathrooms and kitchens must be fully fitted and all service penetrations sealed.
8. All mechanical ventilation turned off with grilles sealed.
9. All trickle vents to windows and doors must be sealed.
10. All fireplaces must be sealed.
11. Ensure water is present in soil pipes.
12. 240v power must be available on site.

If you need an airtightness test, please call us on 01525 303905 or email info@aptsoundtesting.co.uk for a no-obligation quote. If you need more information on how to prepare your building for the air test,, please download our airtightness testing checklist. Alternatively, please visit our website at www.aptsoundtesting.co.uk for more information on our pre-completion testing services.

Commercial Air Tightness Testing Requirements: A Complete Guide

Commercial air tightness testing is a legal requirement for most new commercial buildings across the UK. It plays a vital role in demonstrating compliance with Approved Document L (Part L) of the Building Regulations, helping to ensure that buildings achieve modern standards for energy efficiency, carbon reduction, and overall operational performance.

Whether you’re developing a warehouse, office building, retail unit, school, healthcare facility, industrial unit, or another commercial property, you’ll usually need to prove that your building meets specified air permeability targets before Building Control will issue final approval.

This guide explains everything you need to know about commercial air tightness testing, including when testing is mandatory, what Part L requires, how to prepare successfully, and why achieving a good result benefits your business long after construction has finished.

What Is Commercial Air Tightness Testing?

Commercial air tightness testing, also known as air permeability testing or air pressure testing, measures the amount of uncontrolled air leakage through the external envelope of a building. Using specialist blower door equipment, engineers pressurise and depressurise the building to identify how much air escapes through unintended gaps and openings.

Every commercial building will experience some degree of air leakage. However, excessive leakage significantly reduces energy efficiency by allowing heated or cooled air to escape while permitting external air to enter the building. This forces heating, ventilation and air conditioning (HVAC) systems to work harder, increasing operational costs and reducing occupant comfort.

Poor air tightness can result in:

• Higher heating and cooling costs
• Increased carbon emissions
• Difficulty complying with Part L Building Regulations
• Poor energy performance and EPC ratings
• Draughts and uncomfortable internal environments
• Reduced overall building performance

Many leakage paths are hidden behind finishes or located at complex construction junctions. Common examples include poorly sealed service penetrations, cladding interfaces, structural steel connections, door thresholds and roof junctions. Identifying and addressing these issues early can significantly improve a building’s overall performance and reduce the likelihood of failing the final compliance test.

When Is Commercial Air Tightness Testing Mandatory?

Under Approved Document L2, air tightness testing is mandatory for most newly constructed commercial buildings.

Testing is generally required for:

• All new commercial buildings with a floor area greater than 500 m²
• Large commercial extensions
• Major refurbishments where substantial alterations have been made to the building envelope
• Buildings where Building Control specifically requests verification of air permeability

Even commercial buildings below 500 m² may still require testing if it forms part of the approved energy assessment or Building Control considers it necessary.

The air tightness certificate produced after testing forms an essential part of the Building Regulations compliance package. Without satisfactory results, final sign-off may be delayed until remedial work has been completed and the building successfully retested.

For developers, contractors and project managers, this makes early planning essential. Leaving air tightness until the end of a project often leads to unnecessary delays, additional costs and programme disruption.

Understanding Part L Air Tightness Requirements

Approved Document L establishes the minimum energy efficiency standards for commercial buildings in England. Air tightness forms one of the key performance criteria used to demonstrate compliance.

1. Target Emission Rate (TER)

The building must achieve a calculated carbon emission rate that does not exceed the Target Emission Rate (TER). Excessive air leakage increases heating demand and can make it difficult to satisfy this requirement.

2. Air Permeability Target

Most commercial developments are designed to achieve an air permeability of 10 m³/h·m² at 50 Pascals (Pa) or better.

However, many projects specify significantly lower targets to improve energy efficiency or satisfy sustainability objectives such as BREEAM certification. Modern office buildings, schools and public sector developments frequently require much tighter envelopes than the minimum regulatory standard.

3. Demonstrating Compliance

Once testing has been completed, a formal air tightness test certificate must be submitted to Building Control as evidence that the completed building meets its design specification.

If the measured air permeability exceeds the design target, remedial sealing works will normally be required before the building can be retested.

4. Competent Testing

Testing should only be undertaken by suitably qualified and accredited organisations using calibrated equipment and recognised industry procedures. Selecting an experienced testing provider helps ensure accurate results while providing valuable guidance should remedial works become necessary.

Why Commercial Buildings Fail Air Tightness Tests

Many commercial buildings fail not because of one major defect, but due to hundreds of small leakage paths spread throughout the building envelope.

Some of the most common areas where air leakage occurs include:

• Roller shutter doors
• Loading bay doors
• Service penetrations for ducts, pipes and electrical cables
• Curtain walling interfaces
• Cladding joints
• Structural steel connections
• Roof-to-wall junctions
• Lift shafts
• Mechanical risers
• Door thresholds
• Expansion joints
• Ceiling void penetrations

On large commercial projects, coordination between multiple trades is often the biggest challenge. Electrical contractors, mechanical installers, cladding specialists and drylining contractors all create penetrations through the building envelope, and unless these are correctly sealed, they become significant sources of unwanted air leakage.

Early quality inspections during construction can dramatically reduce the likelihood of discovering problems during the final test.

Preparing for a Successful Air Tightness Test

Good preparation is one of the most effective ways to achieve a first-time pass and avoid costly delays.

Before the test takes place, contractors should ensure that:

• All external doors and windows are fully installed and operational.
• Service penetrations are permanently sealed.
• Internal finishes affecting the building envelope are complete.
• Trickle vents are closed where appropriate.
• Mechanical ventilation systems are switched off or temporarily sealed in accordance with testing procedures.
• Roof hatches, access panels and external openings are properly secured.
• Temporary construction openings have been permanently closed.

For larger or more complex developments, arranging a pre-test inspection can identify potential issues before formal compliance testing begins. This proactive approach often saves significant time and money by highlighting leakage areas while they remain easy to access.

Where buildings fail initial testing, diagnostic techniques such as smoke tracing and thermal imaging can quickly pinpoint leakage paths, allowing contractors to target remedial works rather than relying on trial and error.

The Benefits of Good Air Tightness

Although air tightness testing is a regulatory requirement, the benefits extend far beyond simply obtaining Building Control approval.

A well-sealed commercial building offers significant long-term advantages, including:

Reduced Energy Costs

Heating and cooling systems operate far more efficiently when conditioned air remains inside the building. Lower energy consumption translates directly into reduced operating costs throughout the building’s life.

Improved Occupant Comfort

Reduced draughts create more consistent internal temperatures, improving comfort for employees, customers and building users.

Better EPC Ratings

Improved air tightness contributes to stronger energy performance calculations, helping buildings achieve higher EPC ratings and supporting sustainability objectives.

Lower Carbon Emissions

Reduced energy demand leads directly to lower carbon emissions, helping organisations meet environmental targets and future-proof their property portfolios.

Faster Regulatory Approval

Passing the air tightness test first time avoids delays with Building Control sign-off and helps projects remain on programme.

Increased Asset Value

Buildings with better energy performance are increasingly attractive to occupiers, investors and institutional landlords. Strong environmental performance can enhance rental value while reducing long-term operational expenditure.

As energy prices continue to rise and environmental legislation becomes more demanding, achieving excellent air tightness has become both a compliance requirement and a valuable commercial investment.

Accredited Expertise You Can Trust

Selecting an experienced, accredited testing provider is essential to achieving reliable, repeatable and fully compliant results.

APT Sound Testing is a UKAS-accredited ISO/IEC 17025 testing laboratory specialising in on-site air tightness testing for commercial and large-scale buildings. UKAS accreditation demonstrates that our testing procedures, reporting systems and quality management processes meet the highest recognised technical standards within the UK.

We are also an ATTMA Level 2 Registered Organisation, qualified to undertake testing on Large, Complicated and High-Rise (LCHR) buildings, including phased developments and zonal handovers. In addition, our ATTMA EA accreditation enables us to produce accurate envelope area calculations for complex commercial structures.

With more than 20 years of specialist industry experience, our engineers have successfully delivered testing and consultancy services on some of the UK’s most prestigious and technically demanding developments, including Battersea Power Station and the Imperial War Museum London.

Our combination of accredited competence, advanced testing equipment and practical construction experience allows us to deliver dependable results while helping clients achieve compliance as efficiently as possible.

Book Your Commercial Air Tightness Test

Commercial air tightness testing should never be viewed as a final hurdle at the end of construction. When planned correctly and supported by experienced specialists, it becomes an integral part of delivering an energy-efficient, compliant and high-performing commercial building.

APT Sound Testing provides nationwide commercial air tightness testing using the latest UKAS-calibrated modular blower door systems. We test everything from small commercial units to large warehouses, schools, offices, healthcare facilities and complex multi-storey developments.

Our engineers also provide advanced diagnostic services, including smoke tracing and thermal imaging, enabling us to quickly identify air leakage paths and support remedial works where required. This proactive approach helps maximise the likelihood of achieving a first-time pass while keeping projects on schedule.

If you’re planning a new commercial development or require testing for an existing project, our experienced team is ready to help.

Contact APT Sound Testing today by emailing info@aptsoundtesting.co.uk or call our friendly team on 07775 623464 to arrange your commercial air tightness test and ensure full compliance with UK Building Regulations.

BREEAM Indoor Air Quality Testing – Why It Matters

When it comes to creating healthy, comfortable buildings, indoor air quality is just as important as energy efficiency or acoustic performance. That’s why BREEAM places such a strong focus on ensuring the air inside a building is safe for the people who use it every day.

At APT Sound Testing, we’ve been carrying out BREEAM Indoor Air Quality (IAQ) testing for many years, helping developers, contractors, architects, and project managers achieve valuable BREEAM credits while ensuring buildings meet the highest standards of indoor environmental quality.

Whether you need an Indoor Air Quality Plan, post-construction air quality testing, or expert advice throughout your project, our experienced team is here to make the process straightforward from start to finish.

What is BREEAM Indoor Air Quality Testing?

BREEAM Indoor Air Quality Testing is designed to assess the quality of the air within a newly completed building before it is occupied. The aim is simple – to minimise harmful pollutants and create healthier indoor environments for future occupants.

As part of the assessment, we test for key airborne contaminants, including:

• Total Volatile Organic Compounds (TVOCs)
• Formaldehyde

If required, we can also test for additional pollutants depending on your project’s specific requirements.

The Two Stages of BREEAM Hea02

To achieve the available BREEAM credits under the Hea02 category, there are two important stages.

Stage 1 – Indoor Air Quality Plan (IAQP)

The first step is producing an Indoor Air Quality Plan during the design stage of your project.

This plan helps reduce the risk of poor indoor air quality by considering factors such as ventilation strategies, construction methods, building materials, and future maintenance. By identifying potential sources of contamination early, your project can be designed to provide a healthier environment for everyone who will use the building.

Our bespoke Indoor Air Quality Plans typically include:

• Advice on identifying and removing contamination sources
• Recommendations for controlling and diluting airborne pollutants
• Pre-occupancy flush-out procedures
• A practical checklist to prepare for third-party testing
• Guidance on maintaining good indoor air quality after occupation
• Independent testing and analysis

Stage 2 – Post-Construction Indoor Air Quality Testing

Once construction is complete and the building’s HVAC system is fully operational, it’s time for the post-construction Indoor Air Quality Test.

During our site visit, we collect air samples from representative occupied spaces, such as offices, classrooms, healthcare facilities, apartments, or other regularly occupied rooms.

The samples are analysed to measure pollutant levels against the limits specified by BREEAM. If any readings exceed the required thresholds, we’ll explain the findings clearly and recommend practical steps to help bring the building into compliance.

Why Choose APT Sound Testing?

We’ve helped clients across the UK successfully achieve BREEAM, Home Quality Mark (HQM), and other environmental compliance standards through reliable, accurate Indoor Air Quality Testing.

When you work with APT Sound Testing, you can expect:

• Experienced, qualified testing engineers
• Fixed, competitive quotations with no hidden surprises
• Helpful pre-test guidance to maximise the chances of success
• Testing carried out strictly in accordance with BREEAM Hea02 requirements
• Fast, clear reporting and expert technical advice

We understand that preparation is often the key to achieving compliance, which is why we’re always happy to provide practical advice before we even arrive on site.

Preparing for Your Air Quality Test

A successful Indoor Air Quality Test starts with good preparation. Our team provides a comprehensive checklist to ensure your building is ready before testing begins, helping to avoid unnecessary delays or repeat visits.

If you’re planning a BREEAM assessment, we’d be happy to provide our Indoor Air Quality Testing Checklist to help your project stay on track.

Need BREEAM Indoor Air Quality Testing?

If you’re looking for a trusted partner to carry out your BREEAM Indoor Air Quality Testing, APT Sound Testing is here to help.

From creating your Indoor Air Quality Plan to completing post-construction testing and reporting, we’ll guide you through every stage of the process with friendly advice and professional support.

Get in touch with our team today on 01525 303905 or email info@aptsoundtesting.co.uk to discuss your project. Alternatively, visit our Contact page to request a quotation.

Expert Air Tightness Testing Across the UK

APT Sound Testing provides professional Air Tightness Testing services throughout the United Kingdom, supporting projects of all sizes — from individual residential properties to large-scale commercial developments.

As one of the few companies in the UK accredited by UKAS to undertake both Air and Sound Testing, we provide a complete testing solution that helps clients achieve Building Regulations compliance efficiently. Our experienced engineers can complete Air Tightness, Sound Insulation and Ventilation Testing packages during the same visit, improving site coordination while reducing costs.

Unlike many testing companies, we do not subcontract our work. Every project is completed by our own highly skilled and accredited engineers, ensuring consistent quality, reliability and expert advice from start to finish.

---

Why is Air Tightness Testing Required?

Air Tightness Testing became a legal requirement in England and Wales in 2006 under Building Regulations Part L, which focuses on the conservation of fuel and power.

Today, airtightness testing plays an increasingly important role in creating energy-efficient, low-carbon buildings. Poor airtightness allows uncontrolled air leakage through gaps and cracks in the building fabric, resulting in unnecessary heat loss, increased energy consumption and higher carbon emissions.

Building Regulations define air leakage as the uncontrolled movement of air through the gaps and openings within a building’s structure. In everyday terms, this is what we commonly experience as draughts.

By reducing unwanted air leakage, buildings can retain heat more effectively, improve energy performance and provide a more comfortable environment for occupants.

---

Understanding Air Leakage Rates and Building Performance

When energy is lost through uncontrolled air movement, it contributes to the building’s overall emission rate. New developments must achieve specific air leakage targets to comply with Building Regulations.

For a typical residential property, the target air permeability rate is often around:

5.0m³/hr/m²

For commercial buildings, requirements are usually more demanding, with target rates commonly around:

3.0m³/hr/m² or lower

Achieving these targets requires careful consideration of the building’s air barrier from the early design stage through to construction completion.

---

The Risks of Poor Airtightness

Air leakage affects buildings throughout the year.

Where air enters a building through uncontrolled gaps (infiltration), air usually escapes elsewhere (exfiltration). These unwanted air movements can create a number of problems:

Increased Energy Costs

Air leaking from a building envelope causes additional energy demand because replacement air must be heated or cooled. Air Tightness Testing helps identify leakage rates, allowing designers and building owners to better understand energy performance and optimise heating and cooling systems.

Condensation, Damp and Mould Problems

In winter, warm moist indoor air can escape through gaps in the building fabric and enter colder areas such as wall cavities and roof spaces. This can lead to condensation, mould growth and, over time, timber decay or structural damage.

Reduced Occupant Comfort

Draughts can significantly affect the comfort of people using a building. Cold air entering offices, homes or commercial spaces can create uncomfortable conditions and reduce occupant satisfaction.

APT Sound Testing has investigated buildings where excessive air leakage caused serious workplace comfort issues. In one case, a building recorded an air leakage rate of 25m³/hr/m². After leakage paths were identified and remedial works completed, the building achieved a result below 5m³/hr/m², significantly improving performance.

Increased Risk of External Pollutants Entering Buildings

Uncontrolled air leakage can also allow pollutants from outside to enter a building, including emissions from nearby roads, fuel stations, waste areas, restaurants and other external sources.

A well-designed and properly installed air barrier helps control airflow, improve indoor air quality and reduce the risk of unwanted pollutants entering occupied spaces.

---

How Does Air Tightness Testing Work?

Air Tightness Testing is commonly carried out using a blower door test.

During the test, specialist equipment measures:

• The amount of air moving into or out of the building
• The pressure difference across the building envelope
• The overall air leakage rate

Where leakage is detected, our engineers can use techniques such as smoke testing to accurately locate air leakage paths.

Many buildings do not fail because of one obvious opening; instead, the main issues are often caused by multiple smaller gaps throughout the construction. Identifying these areas early allows corrective action to be taken before final compliance testing.

---

Air Tightness Consultancy and Design Support

APT Sound Testing provides expert air tightness consultancy from the earliest design stages through to final completion testing.

Our team works with architects, developers, contractors and building professionals to help:

• Review building designs and air barrier strategies
• Identify potential leakage risks
• Provide guidance during construction
• Reduce the likelihood of failed air tests
• Achieve Building Control approval

As air tightness targets continue to become more demanding, early consideration of the building’s air leakage line is essential.

By working with us throughout the design and construction process, we can help ensure that airtightness requirements are achieved efficiently and cost-effectively.

---

Combined Air and Sound Testing Packages

Many of our clients choose our combined testing packages because our engineers are accredited to carry out both Air Tightness and Sound Testing.

Our multi-skilled team allows multiple compliance tests to be completed during one coordinated visit, providing:

• Reduced project costs
• Improved site scheduling
• Less disruption for contractors
• Faster completion of compliance requirements

We can also provide out-of-hours testing, including weekend appointments, to minimise disruption to working sites and occupied buildings.

---

Preparing for Your Air Tightness Test

To achieve a successful result, preparation is essential.

We recommend that developers and contractors consider airtightness requirements early and ensure that all elements of the air barrier are correctly installed before testing.

Our team can provide advice and guidance throughout your project, and we offer an air tightness checklist to help you prepare for your test.

---

Why Choose APT Sound Testing?

APT Sound Testing has extensive experience delivering successful air tightness tests across London and throughout the UK.

Our team understands the requirements of Approved Document L and has completed thousands of tests across a wide range of residential and commercial developments.

With expert advice, UKAS accreditation and a commitment to quality, we help clients achieve compliance while improving the energy efficiency and performance of their buildings.

---

Contact APT Sound Testing

If you need professional Air Tightness Testing, consultancy or compliance support, our experienced team is ready to help.

📞 01525 303905
📧 info@aptsoundtesting.co.uk

Contact APT Sound Testing today to discuss your project requirements and discover how our specialist air testing services can help you achieve compliance and improve building performance.

Common Air Leakage Paths: PAS 2035 Air Tightness Testing

One of the key observations from our extensive experience in air tightness testing is that the more complete a development is at the time of testing, the more likely it is to achieve a low air leakage result.

To help our clients prepare, we provide a comprehensive Air Leakage Checklist alongside every quotation. By engaging with projects throughout the retrofit process, we can offer practical advice and guidance on the most effective ways to minimise air leakage and achieve PAS 2035 Compliance first time.

Most Common Air Leakage Paths We Identify

During air tightness and smoke leakage testing, we frequently identify air leakage from:

• Poorly installed windows and doors that do not seal correctly against frames
• Missing or damaged window and door seals
• Faulty or damaged trickle vents
• Gaps at wall and skirting board junctions
• Gaps through existing floorboards on all levels
• Perimeter and internal wall-to-floor junctions
• Service penetrations for electrical, plumbing and mechanical installations
• Ceiling voids connecting to masonry cavity walls
• Eaves and roof cavity pathways
• Gaps around window sills and door reveals
• Bathroom and WC service penetrations
• Kitchen and utility service penetrations
• Gaps between dry lining systems and ceilings
• Unsealed chimneys and fireplaces
• Electrical, data and IT installations
• Loft hatches and access panels
• Ventilation penetrations through walls, roofs and ceilings
• Poorly installed extractor fans in kitchens, utilities and bathrooms

Failed an Air Tightness Test?

If your building doesn’t achieve the required result, there is no need to panic.

Our smoke leakage testing service can accurately identify the source of air leakage throughout the building envelope. We provide a detailed smoke survey report, allowing your team to carry out targeted remedial sealing works before retesting.

How We Can Help

APT Sound Testing has extensive experience supporting PAS 2035 retrofit projects and helping clients achieve compliance with Approved Document L and air tightness requirements.

As a UKAS-accredited ISO/IEC 17025 testing laboratory, we specialise in on-site air tightness testing for commercial and large-scale developments. We are also an ATTMA Level 2 registered organisation, qualified to test Large, Complex and High-Rise (LCHR) buildings, as well as phased and zonal handover projects.

Using the latest UKAS-calibrated Retrotec blower door equipment, our engineers have successfully delivered thousands of air tightness tests across the UK, including landmark developments such as Battersea Power Station and the Imperial War Museum London.

Our combination of accredited competence, technical expertise and over 20 years of industry experience ensures reliable, repeatable and fully compliant testing on every project.

📞 Need help preparing for your PAS 2035 air tightness test?

Preparing for your PAS 2035 air tightness test? Contact the APT Team on 01525 303905 or email info@aptsoundtesting.co.uk to discuss your project and avoid costly delays or test failures.

APT Sound Testing: the Leading Choice for Commercial Air Tightness Testing on Large Buildings

Airtightness has become one of the most important performance metrics in modern commercial construction. As the UK tightens energy‑efficiency requirements under Approved Document L and pushes toward net‑zero targets, developers and contractors must ensure their buildings achieve low air‑leakage rates, reduced heat loss, and long‑term operational efficiency.

APT Sound Testing Ltd has established itself as one of the UK’s leading specialists in commercial air tightness testing, particularly for large and complex buildings. With UKAS accreditation, ATTMA Level 2 certification, advanced multi‑fan blower door systems, and integrated diagnostic tools such as smoke testing and thermal imaging, APT delivers a level of accuracy and insight that few companies can match.

This article explores why APT Sound Testing is the preferred partner for commercial clients—and how their combined testing methodology helps buildings achieve compliance first time.

---

The Importance of Airtightness in Commercial Buildings

Air leakage is one of the biggest contributors to heat loss in commercial buildings. Uncontrolled infiltration can account for 20–40% of total heating demand, especially in older or poorly sealed structures. APT’s blog Measuring the Air Tightness of Buildings explains how leakage affects energy performance and why accurate testing is essential:

Reducing leakage from 12–15 m³/hr/m² to below 5 m³/hr/m² can save thousands of pounds annually in heating costs. For large buildings, the financial and environmental benefits are even greater.

---

High‑Power Multi‑Fan Blower Door Testing for Large Buildings

APT Sound Testing is one of the few UK companies equipped with six‑fan blower door systems, enabling them to test buildings over 10,000 m² in a single setup. This capability is essential for:

• Warehouses and logistics hubs
• Hospitals and healthcare facilities
• Schools and universities
• Office buildings
• Mixed‑use developments

Their blog Our Air Tightness Testing Procedure provides a detailed breakdown of the testing process, including pressure steps, equipment, and compliance requirements:

Using high‑power multi‑fan systems ensures:

• Faster testing
• Minimal disruption
• Highly accurate results
• Full compliance with ATTMA TSL2 and Building Regulations

---

Smoke Testing: Visual Identification of Leakage Paths

While blower door testing quantifies leakage, smoke testing reveals it visually. APT uses small and large scale smoke machines to show exactly where air is escaping or entering the building envelope.

This method is particularly effective for identifying leakage around:

• Raised access floors
• Suspended ceilings
• Service penetrations
• Door sets and lobbies
• Roof junctions
• Wet rooms and plant areas

APT’s blog The Importance of Air Tightness Testing highlights how smoke testing provides immediate clarity for site teams, enabling targeted remedial sealing:

This reduces guesswork and increases the likelihood of passing the final compliance test on the first attempt.

---

Thermal Imaging: The Most Powerful Diagnostic Tool for Hidden Defects

APT’s thermal imaging surveys are carried out by Level 2 and Level 3 certified thermographers using high‑resolution FLIR cameras. Thermal imaging is essential for identifying:

• Missing or damaged insulation
• Cold bridging
• Hidden air leakage
• Moisture ingress
• Poor thermal comfort
• Mould and condensation risks

When combined with blower door depressurisation, thermal imaging becomes even more effective. Cold external air entering the building appears as clear thermal signatures, revealing:

• Poorly sealed windows and doors
• Leaking service penetrations
• Defective roof/wall junctions
• Gaps behind cladding or drylining

APT’s blog Residential Air Tightness Testing– Q&A explains how thermal imaging can uncover issues that would otherwise remain invisible:

---

Why APT’s Combined Approach Delivers the Best Results

APT Sound Testing’s integrated methodology, blower door testing + smoke testing + thermal imaging, provides a complete picture of a building’s airtightness.

This combined approach ensures:

• No leakage path is missed
• Hidden defects are exposed
• Contractors receive clear, actionable guidance
• Remedial works are targeted and efficient
• Compliance is achieved faster

Their blog Air Tightness Testing for PAS2035 reinforces how diagnostic‑rich testing supports both compliance and long‑term building performance:

---

Regulatory Compliance and BREEAM Benefits

APT’s testing approach aligns with:

• Approved Document L2A – New non‑dwellings
• Approved Document L2B – Existing non‑dwellings

Thermal imaging also contributes to BREEAM credits, making it a valuable tool for sustainable building certification.

---

Why Commercial Clients Choose APT Sound Testing Ltd

UKAS Accredited Testing

Ensures full compliance with Building Regulations and industry standards.

Expertise in Large and Complex Buildings

Engineers are ATTMA Level 2 certified and highly experienced in large‑scale commercial testing.

Advanced Diagnostic Capability

Few companies offer integrated blower door, smoke, and thermal imaging surveys at this level.

Fast Reporting and Clear Contractor Guidance

Reports are designed for site teams—clear, actionable, and technically robust.

Nationwide Coverage

APT can respond quickly to projects across the UK.

Over 22 Years of Experience

A long‑established specialist with a proven track record.

---

Conclusion: APT Delivers Compliance, Efficiency, and Long‑Term Value

For developers, contractors, and building owners, airtightness is not just a compliance checkbox, it is a long‑term investment in energy performance, operational efficiency, and occupant wellbeing.

APT Sound Testing Ltd stands out because they don’t just test buildings, they diagnose, explain, and solve airtightness problems. Their integrated approach, advanced equipment, and highly trained engineers make them one of the UK’s leading providers for large‑scale commercial air testing.

---

Contact APT Sound Testing Ltd

If you would like to arrange commercial air tightness testing, smoke testing, or thermal imaging for your project, APT Sound Testing Ltd offers nationwide coverage and rapid response times.

APT Sound Testing Ltd
Phone: 07775 623464
Email: info@aptsoundtesting.co.uk
Website: https://aptsoundtesting.co.uk

For more technical guidance, case studies, and insights, visit the APT Sound Testing blog: https://aptsoundtesting.co.uk/blog/

High-Capacity Air Tightness Testing for Buildings Over 10,000 m²

As building regulations tighten and energy performance standards continue to rise, airtightness testing has become a critical part of modern construction. For large commercial and industrial developments, achieving compliance is no longer just about meeting regulations — it’s about improving long-term efficiency, reducing operational costs, and ensuring high-quality construction standards.

However, testing very large buildings requires far more than standard equipment and basic experience.

APT Sound Testing is one of the few specialist companies in the UK with the capability to carry out air pressure testing on buildings exceeding 10,000 m². Backed by a high-powered 6-fan blower door system, Level 2 ATTMA registration, and UKAS accreditation, we provide reliable, accurate, and fully compliant airtightness testing for even the most complex projects.

Specialist Equipment for Very Large Buildings

Most air tightness testing companies operate with one or two fans, which is generally sufficient for residential properties and smaller commercial units. Large-scale developments, however, demand significantly greater airflow and testing capacity.

APT Sound Testing has invested in an advanced multi-fan blower door system specifically designed for testing large-volume buildings, including:

• Warehouses and logistics centres
• Supermarkets and large retail developments
• Schools, hospitals, and public sector buildings
• Multi-storey residential developments
• Industrial and manufacturing facilities
• Buildings with complex internal zoning

Our high-capacity system allows us to maintain stable test pressures across vast internal spaces while delivering highly accurate results. This not only ensures compliance with ATTMA TSL1, TSL2, and Part L requirements, but also reduces testing time and minimises disruption to construction programmes.

For buildings over 10,000 m², this level of capability is essential — and still relatively rare within the industry.

Why Accreditation Matters

Large-scale airtightness testing is not simply about using larger fans. It requires technical expertise, precise procedures, and recognised accreditation to ensure results are accepted by Building Control and project stakeholders.

APT Sound Testing is:

• Level 2 ATTMA Registered — authorised to test large, complex, and multi-zone buildings
• UKAS Accredited — providing independently verified testing procedures and traceable results

This gives contractors, developers, and consultants complete confidence that testing is carried out to the highest industry standards.

Our accreditation helps clients achieve:

• Compliance with Building Regulations Part L
• Acceptance by Building Control and warranty providers
• Support for BREEAM and sustainability targets
• Reduced risk of costly retesting or project delays

For large and high-value developments, using an accredited testing provider is essential to avoid unnecessary complications later in the programme.

Advanced Air Leakage Diagnostic Surveys

Achieving airtightness on large buildings can be challenging. Minor defects repeated across thousands of square metres can quickly lead to significant leakage rates.

To help identify and resolve problems efficiently, APT Sound Testing provides detailed air leakage diagnostic surveys using advanced testing methods.

Smoke Testing

Under pressurised conditions, smoke testing visually identifies leakage paths throughout the building envelope, including:

• Cladding interface failures
• Poorly sealed service penetrations
• Faulty window and door seals
• Roof-to-wall junction leakage
• Hidden construction gaps and voids

This allows contractors to pinpoint issues quickly and carry out targeted remedial works.

Thermal Imaging Surveys

Thermal imaging inspections are another highly effective diagnostic tool, especially when combined with depressurisation testing.

Thermal imaging can identify:

• Cold air infiltration
• Missing or poorly installed insulation
• Thermal bridging
• Hidden air leakage not visible during visual inspections

These surveys provide valuable insight into both airtightness performance and overall building envelope quality.

Detailed Leakage Reporting

APT Sound Testing provides comprehensive reports designed to help site teams resolve issues quickly and efficiently.

Our reports include:

• Annotated photographs and thermal images
• Leakage severity assessments
• Root-cause analysis
• Recommended remedial actions
• Prioritised sealing guidance

This structured approach helps contractors achieve compliance faster while avoiding unnecessary remedial costs.

Why Large Buildings Need Specialist Testing

Testing a building over 10,000 m² is fundamentally different from testing smaller properties. It requires:

• High-capacity blower door systems
• Advanced airflow measurement
• Multi-zone testing strategies
• Experienced engineers
• Robust diagnostic procedures
• Accredited reporting methods

Without the correct expertise and equipment, test results can become unreliable — potentially leading to failed compliance, programme delays, and expensive retesting.

APT Sound Testing removes these risks by providing a complete large-building airtightness testing solution from initial consultation through to final certification.

Supporting Projects from Design to Completion

Modern construction programmes are demanding, and airtightness performance must often be achieved within tight timescales.

APT Sound Testing supports clients throughout the entire process with services including:

• Design-stage consultancy
• Pre-test inspections
• Large-scale air pressure testing
• Diagnostic leakage surveys
• Remedial guidance and support
• Fast-turnaround reporting

Our objective is simple: help projects achieve compliance first time.

Airtightness Testing for BREEAM and Energy Efficiency

For developments targeting BREEAM certification, improved EPC ratings, or enhanced energy performance, airtightness plays a major role in overall building efficiency.

Our testing services support:

• BREEAM Hea 02 and Ene 01 credits
• Improved EPC and SBEM calculations
• Reduced heating and cooling demand
• Lower long-term operational energy costs

On large buildings, even small improvements in airtightness can result in significant energy savings over the building’s lifespan.

Why Choose APT Sound Testing?

APT Sound Testing is trusted nationwide for large-scale airtightness testing because we combine specialist equipment with accredited expertise.

Our services include:

• High-powered blower door systems for buildings above 10,000 m²
• Level 2 ATTMA Registered testing
• UKAS Accredited procedures
• Smoke testing and thermal imaging diagnostics
• Detailed and actionable reporting
• Fast turnaround times
• Nationwide coverage

We continue to support contractors, developers, architects, and consultants across the UK on some of the country’s most demanding airtightness projects.

Contact APT Sound Testing

For large-scale air pressure testing, air leakage diagnostics, or technical advice, contact APT Sound Testing today.

Phone: 07775 623464
Email: info@aptsoundtesting.co.uk
Website: https://aptsoundtesting.co.uk/

Air Tightness Testing – APT Sound Testing

At APT Sound Testing, we provide professional Air Tightness Testing services across the United Kingdom, supporting projects of all sizes, from single residential dwellings to large-scale commercial developments. Our experienced team works closely with developers, contractors, and property owners to ensure buildings meet the required performance standards and achieve compliance with UK Building Regulations.

What sets us apart is that we are UKAS-accredited to carry out both Air and Sound Testing in accordance with Building Regulations and industry standards. Because our engineers are multi-skilled and fully accredited, we can perform Air, Sound, and Ventilation Testing during the same visit. This combined approach saves our clients time and money while improving on-site coordination. Unlike many providers, all of our testing is carried out by our own in-house engineers, we never subcontract our work.

---

Why Air Tightness Testing Is Required

Air tightness testing became a legal requirement in 2006 in England and Wales under Building Regulations Part L, which focuses on the conservation of fuel and power. The goal is to create more energy-efficient buildings by reducing uncontrolled air leakage.

Air leakage refers to the uncontrolled movement of air through gaps, cracks, and joints in the building fabric, something most people simply recognise as draughts.

Reducing these air leakage paths helps:

• Improve energy efficiency
• Reduce carbon emissions
• Lower heating and cooling costs
• Improve indoor comfort

When energy escapes through a building’s fabric, it contributes to what is known as the Building Emission Rate (BER). To meet regulatory standards, new developments must achieve specific air leakage targets.

Typical targets include:

• Standard dwellings: around 5.0 m³/hr/m²
• Commercial buildings: often 3.0 m³/hr/m² or lower

---

The Impact of Poor Air Tightness

Air infiltration and exfiltration occur simultaneously in buildings. If air enters in one location, it must exit somewhere else.

Poor air tightness can lead to several problems:

1. Increased Energy Loss

Air leaking out of a building must be replaced by conditioned air that needs heating or cooling. This significantly increases energy consumption and operational costs.

2. Condensation and Moisture Issues

In winter, warm indoor air can escape into colder wall cavities where moisture condenses. This can lead to:

• Mould growth
• Rot
• Structural damage
• Poor indoor air quality

3. Indoor Comfort Problems

Draughts can make buildings uncomfortable for occupants. In extreme cases, excessive air leakage can disrupt normal building use.

For example, during one investigation we conducted smoke testing on a building where employees refused to work due to constant draughts. The building had an air leakage rate of 25 m³/hr/m². After identifying and sealing the leakage paths, the building achieved below 5 m³/hr/m², resolving the issue.

4. Pollution Ingress

Excessive air leakage can draw polluted air into buildings from nearby sources such as:

• Busy roads
• Fuel stations
• Waste areas
• Restaurants

Creating a well-sealed air barrier helps control indoor air quality and minimise pollutant entry.

---

Our Air Tightness Testing Process

At APT Sound Testing, we use professional blower door testing equipment to measure air leakage accurately.

Step 1: Install the Blower Door System

Our fan system is mounted into a standard door opening (approximately 900mm x 2000mm) and adjusted to fit securely within the frame.

Step 2: Environmental Measurements

Before testing begins, we record environmental data including:

• Internal and external temperatures
• Barometric pressure
• Ambient conditions

Step 3: Pressure Testing

The fan system is activated and pressure readings are taken between 25 Pa and 70 Pa in 5 Pa increments. These readings allow us to measure airflow through the building envelope.

Step 4: Final Calculations

Once measurements are complete, our technicians calculate the air leakage rate at 50 Pascals (m³/h·m² @ 50Pa) based on the airflow required to maintain that pressure difference.

Step 5: Smoke Testing (Leak Detection)

The building is then pressurised to around 50 Pascals, forcing air through any gaps or leakage paths. Using smoke testing equipment, our engineers walk through the property to identify and record the exact locations of air leaks.

This diagnostic stage helps contractors quickly locate and seal problem areas.

---

How Long Does Testing Take?

A typical air tightness test and smoke investigation usually takes 2–3 hours per building.

However, we can remain on site for the full day if required. This allows contractors to carry out sealing works immediately, followed by re-testing if necessary.

If you plan to undertake remedial work during the test day, it is helpful to have materials such as:

• Mastic sealant
• Expanding foam
• Draught excluders
• Plasterboard
• Grip fill adhesive
• Safe access equipment

---

Air Tightness Consultancy and Design Support

Achieving the required air tightness target is becoming increasingly challenging as regulations continue to tighten. That is why we strongly recommend considering air leakage control during the design stage of a project.

Our consultancy services include:

• Air tightness design reviews
• Construction stage advice
• Pre-completion testing support
• Leakage investigation and reporting

By working with our clients throughout the design and construction process, we can help identify potential issues early and significantly reduce the risk of failing the final test.

---

Combined Air and Sound Testing Packages

Most of our clients now choose our combined pre-completion testing packages, which include:

• Air Tightness Testing
• Sound Insulation Testing
• Ventilation Testing

Because our engineers are UKAS accredited in multiple disciplines, we can complete all tests during the same site visit. This eliminates the need to coordinate multiple companies and greatly simplifies site scheduling.

Additional benefits include:

• Reduced testing costs
• Faster project completion
• Improved on-site coordination

We also offer out-of-hours testing, including weekend appointments, to minimise disruption during working hours.

---

Nationwide Air Tightness Testing You Can Trust

APT Sound Testing has extensive experience conducting thousands of successful air tightness tests across London and the UK. Our knowledgeable consultants provide friendly, practical advice to help your project meet regulatory requirements quickly and efficiently.

If you’re preparing for an upcoming test, we also provide a helpful air tightness checklist to ensure your building is fully prepared.

---

✅ Need help with air tightness testing?
Contact our team today to discuss your project requirements and receive expert guidance from our experienced air tightness consultants. Call 01525 303905 or email: info@aptsoundtesting.co.uk and we will respond as quickly as we can.