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.

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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

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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.

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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.

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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

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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.

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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.

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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.

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✅ 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.

Air Tightness Testing Across the UK

At APT Sound Testing, we provide comprehensive air tightness testing services throughout the United Kingdom. Our experienced team works on projects of all sizes — from single residential dwellings to large-scale commercial developments.

We are proud to be one of the few UKAS-accredited companies qualified to carry out both Air and Sound Testing in full compliance with UK Building Regulations and Standards. This accreditation allows us to deliver combined Air, Sound, and Vent Testing packages during a single site visit — saving our clients time, reducing costs, and improving on-site coordination. Importantly, we never subcontract our testing work; all services are delivered by our fully trained in-house engineers.

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Why Air Testing Matters

Since 2006, air testing has been a legal requirement in England and Wales under Part L of the Building Regulations. Its importance continues to grow as the construction industry focuses on reducing carbon emissions and improving energy efficiency.

Part L defines air leakage as the uncontrolled flow of air through gaps and cracks in a building’s structure — commonly known as draughts. When buildings lose energy through their fabric, this contributes to the building emission rate (BER). To meet regulatory approval, new developments must achieve strict air permeability targets:

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

Improving airtightness reduces unnecessary heat loss, lowers energy consumption, and contributes to greener, more sustainable buildings.

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The Risks of Poor Air Tightness

Air infiltration and exfiltration can create a range of issues:

• Energy Loss: Escaping air must be replaced and conditioned, increasing heating and cooling demands.
• Condensation & Mould: In winter, warm moist air entering cold cavities can cause condensation, mould growth, and structural damage.
• Uncomfortable Draughts: Uncontrolled airflow can make both residential and commercial properties unpleasant to occupy.
• Indoor Air Quality Concerns: Air leakage can allow polluted external air to enter buildings, particularly in locations near busy roads, fuel stations, restaurants, or waste storage areas.

We have previously tested buildings with air leakage rates as high as 25 m³/hr/m² — far above acceptable levels. After identifying and sealing leakage paths, the same buildings were brought below 5 m³/hr/m², dramatically improving comfort and performance.

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Our Consultancy & Pre-Completion Support

Achieving compliance starts at the design stage. We offer air tightness consultancy and detailed design reviews to help ensure your project meets its targets first time.

Our support includes:

• Early-stage air leakage line design advice
• Pre-completion inspections
• On-site testing for building control sign-off
• Weekend and out-of-hours testing services to minimise disruption

To avoid costly failures, we strongly recommend considering air barrier design as early as possible in your project.

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Combined Air & Sound Testing Packages

Because our multi-skilled engineers are UKAS accredited for both disciplines, we offer significant savings through combined testing packages. Our popular “3-Step Pre-Completion Package” allows clients to avoid employing multiple contractors, simplifying project management and improving efficiency.

By conducting both tests on the same day in a structured and coordinated manner, we help streamline site operations and reduce downtime.

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What Is a Blower Door Test?

Air tightness testing is carried out using blower door equipment, which measures:

• The airflow entering or leaving a building
• The pressure difference across the building envelope

This data helps estimate energy performance under various weather conditions and supports equipment sizing and energy consumption predictions.

Using blower door and smoke testing, we can accurately locate leakage paths. While some issues stem from large, obvious gaps, more often it is multiple smaller leaks that contribute most significantly to poor results. Our experienced engineers quickly identify and document these areas so corrective action can be taken efficiently.

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Protecting Energy Performance and Occupant Health

Excessive air leakage can:

• Increase heating and cooling costs
• Cause condensation, mould, and rot
• Reduce occupant comfort
• Allow outdoor pollutants to enter the building

A well-designed and properly installed air barrier is essential for controlling both air quality and air quantity within a building.

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Work With Experienced Air Tightness Specialists

APT Sound Testing has extensive experience delivering thousands of successful air tightness tests across London and the wider UK. Our in-depth knowledge of Approved Document L ensures your development is supported from concept through to completion.

By working collaboratively with clients throughout the design and construction phases, we help identify practical solutions to minimise air leakage and achieve compliance first time.

If you are preparing for an upcoming test, we recommend reviewing an air tightness checklist to ensure your project is ready.

For friendly, expert advice tailored to your development, contact our team today on 01525 303905 or via our online contact form to discuss your air testing requirements.

Why Is Air Tightness Testing Important?

Maintaining a continuous and well-sealed air tightness barrier is essential for any building’s energy efficiency. Air tightness testing measures how much air escapes from inside the building to the outside through unintended gaps or leaks. When air leaks occur, they not only cause uncomfortable draughts but also significantly reduce energy performance.

A poorly sealed building can lose up to 50% of its heat through air leakage. This undermines the benefits of investing in energy-saving measures such as additional insulation, high-efficiency boilers, or renewable heating systems like ground source heat pumps.

Prioritising air tightness testing ensures your building performs as designed—helping you save money on energy bills and meet regulatory requirements. In fact, failing an air tightness test could prevent you from achieving Building Control sign-off and handing over the property.

By carrying out a test, you’ll receive a measurable air leakage rate (in m³/hr/m²), which indicates the volume of air lost or gained. This figure is then compared to the limits set by Building Regulations, determining whether the property meets compliance standards.

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What Building Regulations Govern Air Tightness Testing?

Air tightness testing is required under two main parts of UK Building Regulations:

• Part L1A – Governs air tightness for all new dwellings.
• Part L2A – Applies to commercial and public buildings such as offices, schools, and retail spaces.

Compliance with these regulations is enforced by Building Control.

Air tightness testing is also a crucial component of both SAP (Standard Assessment Procedure) calculations for domestic buildings and SBEM (Simplified Building Energy Model) assessments for commercial ones. These assessments determine a building’s overall carbon footprint, which is directly influenced by how airtight the structure is.

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What Happens if the Building Fails the Air Tightness Test?

At Air Pressure Testing, our goal is for your building to pass the first time. However, if the initial test doesn’t meet the required standard, we’ll work with you to identify and resolve the issues quickly to ensure a successful retest.

Some of the diagnostic techniques we use include:

• Commercial Smoke Testing: We fill the building with smoke and then pressurise it to highlight leakage points — the smoke visibly escapes through gaps in the envelope. For smaller properties, we use handheld “smoke pencils” to pinpoint problem areas.
• Thermal Imaging: Using infrared cameras, we can identify hot and cold spots throughout the building, helping locate areas of heat loss and air leakage.

Unlike some testing companies that simply test and leave, we provide a proactive support service, assisting you until your building achieves full compliance and Building Control approval.

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Common Causes of Air Leakage

Air leakage can occur in many areas, often due to construction detailing or poor installation. The most common problem areas include:

• Junctions between external walls and floors
• Behind fitted kitchen or bathroom units
• Around poorly sealed windows and doors
• Around service penetrations (pipes, ducts, cables, etc.)
• Through attic or loft access doors

By addressing these weak points early in the construction process, you can dramatically reduce the likelihood of air tightness test failures later on.

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Need Expert Air Tightness Testing?

If you’d like more information about our air tightness testing and consultancy services, please don’t hesitate to contact Air Pressure Testing on 01525 303905, or visit our website to learn how we can help your project achieve full compliance and energy efficiency.

Why Your Building Needs an Air Tightness Test

When it comes to energy efficiency, keeping a building’s air barrier continuous and leak-free is essential. Air tightness testing measures how much air escapes from inside a building to the outside at low pressure. Even small leaks can create cold draughts and dramatically increase energy use.

Why Air Tightness Matters

Up to 50% of a building’s heat can be lost through an unsealed envelope. That means the money you invest in high-performance insulation, premium boilers, or ground-source heat pumps can be wasted if the structure isn’t airtight. A failed air test can also delay handover, adding cost and frustration to any project.

Testing provides a clear air-leakage figure (measured in m³/hr/m²), which is then compared to the limits set by building regulations. This ensures the property meets efficiency standards and gives you a benchmark for improvements.

Building Regulations to Know

Two main UK regulations govern air tightness:

• Part L1A – for new dwellings
• Part L2A – for commercial spaces such as offices and public buildings

Compliance is checked by Building Control and feeds into energy assessments: SAP (domestic) and SBEM (commercial). Both evaluate a building’s carbon footprint, where airtightness plays a major role.

If Your Building Fails the Test

A first-time pass is the goal, but if your property falls short, targeted diagnostics can identify the leaks:

• Commercial Smoke Testing – Pressurising the building while filling it with smoke reveals hidden gaps as smoke escapes. Smaller properties can use handheld “smoke pencils.”
• Thermal Imaging – Infra-red cameras highlight hot and cold spots, showing exactly where air is leaking.

Unlike companies that simply test and walk away, a good testing service will work with you to plan fixes and retest for compliance.

Common Air Leakage Points

Addressing these trouble spots early can prevent failed tests:

• External wall/floor junctions
• Behind fitted kitchen or bathroom units
• Around poorly sealed windows and doors
• Around service penetrations (pipes, cables, vents)
• Through attic hatches or loft doors

Bottom Line

Air tightness testing is more than a regulatory checkbox, it’s key to comfort, lower bills, and a reduced carbon footprint. By planning for airtight construction from the start and working with a proactive testing team, you’ll protect your investment and ensure your building performs as efficiently as possible.

For expert testing or consultancy, visit the Air Pressure Testing website or call 01525 303905.

Why Air Tightness Testing Matters

In an era where energy efficiency and environmental responsibility are top priorities in the construction industry, air tightness testing has become an essential part of building compliance. Since 2006, it has been a legal requirement in England and Wales under Building Regulations Part L. But beyond legal obligations, air testing plays a crucial role in reducing energy consumption, minimising environmental impact, and improving indoor comfort.

At APT Sound Testing, we offer professional and reliable Air Tightness Testing services across the UK, working with a wide range of clients, from private homeowners and developers to large-scale commercial contractors. What sets us apart is our commitment to quality, our comprehensive services, and our status as one of the few UKAS-accredited companies able to carry out both air and sound testing under one roof.

The Importance of Air Tightness Testing

Air tightness refers to how well a building can prevent the uncontrolled flow of air through gaps and cracks in its structure. In layman’s terms, it’s about reducing draughts and unwanted ventilation that leads to energy loss. Building Regulations refer to this as “air leakage,” and the more airtight a building is, the more energy efficient it becomes.

If a building isn’t airtight, heated or cooled air can escape, making heating and cooling systems work harder. This not only increases energy bills but also contributes to higher carbon emissions. In response, regulations now require new developments to meet specific air permeability rates, usually around 5.0 m³/hr/m² for residential dwellings. Commercial properties often face even stricter standards, with targets as low as 3.0 m³/hr/m².

But airtightness isn’t just about energy efficiency. It also affects the long-term health of a building. For example, in colder months, moist indoor air can escape into the walls and cause condensation within cavities. This can lead to mould, damp, and even structural rot, all of which are expensive and disruptive to fix.

Comprehensive Testing Packages

APT Sound Testing is uniquely positioned to help developers meet their compliance goals efficiently and cost-effectively. We provide combined Air, Sound, and Vent Testing packages, often completing all three during a single site visit. This streamlined approach not only saves money but also improves on-site coordination and reduces delays.

We believe in doing the job properly, so unlike many other providers, we never subcontract our work. Our in-house team of multi-skilled, UKAS-accredited engineers carry out all testing to the highest professional standards.

Many of our clients take advantage of our three-step pre-completion package, which includes:

1. Air Tightness Testing – to assess and reduce air leakage.
2. Sound Insulation Testing – to ensure acoustic performance between walls and floors meets regulatory standards.
3. Ventilation Testing – to verify that airflow systems meet design specifications and building codes.

This all-in-one solution means fewer contractors to manage, fewer appointments to schedule, and faster results.

Support from Design to Completion

Achieving air tightness begins long before the test itself. At APT Sound Testing, we provide design-stage consultancy to identify potential problem areas before construction even begins. Our experienced consultants review architectural drawings and offer expert advice on construction techniques and materials that will help your project meet its targets.

This early intervention helps avoid costly delays or retesting later on. We also conduct on-site inspections and walkthroughs to ensure the building is prepared before the final air test, significantly increasing the chance of a first-time pass.

Flexible Testing to Suit Your Schedule

We understand that construction sites are busy places, often running on tight deadlines. That’s why we offer flexible scheduling, including weekend and out-of-hours testing. This ensures your project stays on track without disrupting other critical work during normal hours.

Whether you’re managing a small residential build or a major commercial development, our goal is to make the compliance process as smooth and stress-free as possible.

Expert Advice and Friendly Service

Our clients appreciate our professional yet approachable service. We’re always happy to answer questions, explain procedures, and work closely with your site team to ensure successful outcomes.

Whether you’re new to air testing or an experienced builder looking for a reliable partner, we’re here to help. Our team of air tightness experts can provide tailored advice based on your project’s unique needs.

Get in Touch

If you need assistance with air tightness testing, or would like to explore our full suite of compliance services, contact APT Sound Testing today. Use our simple online contact form or call our offices at 01525 303905 to speak with one of our knowledgeable consultants.

We’re ready to support your project from planning through to completion with professional service, competitive pricing, and industry-leading expertise.